Grenoble, France

The Grenoble Institute of Technology is a French technological university system consisting of six engineering schools.Grenoble INP also has a 2 year preparatory class programme, an adult education department, as well as 35 laboratories and a graduate school in Engineering science. More than 1,100 engineers graduate every year from Grenoble INP, making it France's biggest grande école.Most of Grenoble INP is located in Grenoble, except for the ESISAR which is located in Valence. Wikipedia.


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Brechet Y.,Grenoble Institute of Technology | Embury J.D.,McMaster University
Scripta Materialia | Year: 2013

The objective of this introduction to the viewpoint set on architectured materials is to illustrate the paradigm shift which occurs by introducing additional length scales into a material in addition to those provided by the microstructure. This provides new opportunities both to relate the processing of materials directly to design needs and to develop a variety of multifunctional materials in which both the microstructure and the overall architecture of the material are optimized. © 2012 Published by Elsevier Ltd.


Consonni V.,Grenoble Institute of Technology
Physica Status Solidi - Rapid Research Letters | Year: 2013

GaN nanowires, also called nanocolumns, have emerged over the last decade as promising nanosized building blocks for a wide variety of optoelectronic devices. In contrast to other III-V semiconductors, GaN nanowires have the ability to grow catalyst-free within the self-induced approach by plasma-assisted molecular beam epitaxy, which does not require the use of any foreign materials or patterned substrate. The self-induced growth has accordingly been considered as a valuable growth mode to form GaN nanowires on a wide number of substrates such as Si, Al2O3, diamond or SiC. The formation mechanisms have extensively been investigated and are specifically reviewed here from the very onset of the nucleation phase through the elongation phase to the coalescence process. A general approach of the self-induced growth of GaN nanowires is gained. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


De Boissieu M.,Grenoble Institute of Technology
Chemical Society Reviews | Year: 2012

We review some of the results obtained for the study of phason, phonon and atomic dynamics in quasicrystals. In the framework of the hydrodynamic theory long-wavelength phason modes are characteristic of quasicrystal and are diffusive modes. Quenched-in phason mode gives rise to a characteristic diffuse scattering, observed in all the 'stable' icosahedral quasicrystals studied so far. In the AlPdMn icosahedral phase, above T = 500 °C, equilibrium phason modes are shown to be diffusive modes in agreement with the hydrodynamic theory. The lattice dynamics has been studied by inelastic neutron or X-ray scattering. Well defined acoustic modes are only observed for wavevectors smaller than 0.3 Å -1. Above this value, the mode rapidly broadens as a result of mixing with higher energy modes. We show that the results can be interpreted using the concept of pseudo-Brillouin zone boundary and can qualitatively explain the differences observed in the response function of the ZnSc 1/1 approximant and its quasicrystalline counterpart. The observations are qualitatively and quantitatively reproduced using oscillating pair potentials, which open the route for a detailed analysis of the lattice dynamics at the atomic scale. An exceptional dynamical flexibility is also evidenced in the 1/1 approximant. A brief discussion on the implication of those results on the stabilizing mechanisms of quasicrystals is given at the end of the paper. © 2012 The Royal Society of Chemistry.


Dufresne A.,Grenoble Institute of Technology
Materials Today | Year: 2013

Owing to the hierarchical structure of cellulose, nanoparticles can be extracted from this naturally occurring polymer. Multiple mechanical shearing actions allow the release of more or fewer individual microfibrils. Longitudinal cutting of these microfibrils can be achieved by a strong acid hydrolysis treatment, allowing dissolution of amorphous domains. The impressive mechanical properties, reinforcing capabilities, abundance, low density, and biodegradability of these nanoparticles make them ideal candidates for the processing of polymer nanocomposites. With a Young's modulus in the range 100-130 GPa and a surface area of several hundred m2 g-1, new promising properties can be considered for cellulose. © 2013 Elsevier Ltd.


Vu N.-S.,Grenoble Institute of Technology | Caplier A.,Grenoble Institute of Technology
IEEE Transactions on Image Processing | Year: 2012

A good feature descriptor is desired to be discriminative, robust, and computationally inexpensive in both terms of time and storage requirement. In the domain of face recognition, these properties allow the system to quickly deliver high recognition results to the end user. Motivated by the recent feature descriptor called Patterns of Oriented Edge Magnitudes (POEM), which balances the three concerns, this paper aims at enhancing its performance with respect to all these criteria. To this end, we first optimize the parameters of POEM and then apply the whitened principal-component-analysis dimensionality reduction technique to get a more compact, robust, and discriminative descriptor. For face recognition, the efficiency of our algorithm is proved by strong results obtained on both constrained (Face Recognition Technology, FERET) and unconstrained (Labeled Faces in the Wild, LFW) data sets in addition with the low complexity. Impressively, our algorithm is about 30 times faster than those based on Gabor filters. Furthermore, by proposing an additional technique that makes our descriptor robust to rotation, we validate its efficiency for the task of image matching. © 2011 IEEE.


Proville L.,CEA Saclay Nuclear Research Center | Rodney D.,Grenoble Institute of Technology | Marinica M.-C.,CEA Saclay Nuclear Research Center
Nature Materials | Year: 2012

Crystal plasticity involves the motion of dislocations under stress. So far, atomistic simulations of this process have predicted Peierls stresses, the stress needed to overcome the crystal resistance in the absence of thermal fluctuations, of more than twice the experimental values, a discrepancy best-known in body-centred cubic crystals. Here we show that a large contribution arises from the crystal zero-point vibrations, which ease dislocation motion below typically half the Debye temperature. Using Wigner's quantum transition state theory in atomistic models of crystals, we found a large decrease of the kink-pair formation enthalpy due to the quantization of the crystal vibrational modes. Consequently, the flow stress predicted by Orowan's law is strongly reduced when compared with its classical approximation and in much closer agreement with experiments. This work advocates that quantum mechanics should be accounted for in simulations of materials and not only at very low temperatures or in light-atom systems. © 2012 Macmillan Publishers Limited. All rights reserved.


Controlling ferromagnetic/antiferromagnetic blocking temperatures in exchange biased based devices appears crucial for applications. The blocking temperature is ascribed to the ability of both antiferromagnetic grains and interfacial spin-glass-like phases to withstand ferromagnetic magnetization reversal. To better understand the respective contributions of grains versus spin-glass, blocking temperature distributions were measured after various thermal treatments for cobalt/iridium-manganese bilayers. The high-temperature contribution linked to antiferromagnetic grains shifts towards lower temperatures above a threshold thermal annealing. In contrast, the occurrence and evolution of training effects for the low-temperature contribution only agree with its inferred interfacial spin-glass-like origin. © 2013 American Institute of Physics.


Sebo A.,Grenoble Institute of Technology
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics) | Year: 2013

We prove the approximation ratio 8/5 for the metric {s,t}-path-TSP, and more generally for shortest connected T-joins. The algorithm that achieves this ratio is the simple "Best of Many" version of Christofides' algorithm (1976), suggested by An, Kleinberg and Shmoys (2012), which consists in determining the best Christofides {s,t}-tour out of those constructed from a family ℱ+ of trees having a convex combination dominated by an optimal solution x* of the Held-Karp relaxation. They give the approximation guarantee √5+1/2 for such an {s,t}-tour, which is the first improvement after the 5/3 guarantee of Hoogeveen's Christofides type algorithm (1991). Cheriyan, Friggstad and Gao (2012) extended this result to a 13/8-approximation of shortest connected T-joins, for |T| ≥ 4. The ratio 8/5 is proved by simplifying and improving the approach of An, Kleinberg and Shmoys that consists in completing x*/2 in order to dominate the cost of "parity correction" for spanning trees. We partition the edge-set of each spanning tree in ℱ+ into an {s,t}-path (or more generally, into a T-join) and its complement, which induces a decomposition of x*. This decomposition can be refined and then efficiently used to complete x*/2 without using linear programming or particular properties of T, but by adding to each cut deficient for x*/2 an individually tailored explicitly given vector, inherent in x*. A simple example shows that the Best of Many Christofides algorithm may not find a shorter {s,t}-tour than 3/2 times the incidentally common optima of the problem and of its fractional relaxation. © 2013 Springer-Verlag.


Lin N.,Grenoble Institute of Technology | Dufresne A.,Grenoble Institute of Technology
Macromolecules | Year: 2013

Impressive mechanical properties and reinforcing capability make cellulose nanocrystal (CN) a promising candidate as biomass nanofiller for the development of polymer-based nanocomposites. With the recent announcement of large-scale CN production, the use of industrial processing techniques for the preparation of CN-reinforced nanocomposites, such as extrusion, is highly required. However, low thermal stability of sulfuric acid-prepared CN limits the processing since most polymeric matrices are processed at temperatures close to 200 °C or above. It has been proved that surface adsorption of polymers on CN as compatibilizer, such as hydrophilic polyoxyethylene (PEO), can improve its thermal stability due to the shielding and wrapping of PEO. However, the weak combination between CN and PEO allows the free movement of surface polymer, which can induce the self-aggregation of CN and microphase separation in composites especially during melt processing. Using carboxylation-amidation reaction, short chains poly(ethylene glycol) (PEG) can be first grafted on the surface of the nanocrystals, and immobilize long PEO chains on modified nanocrystals through physical adsorption and entanglement. Two polymeric layers should further improve the thermal stability of CNs, and surface polymeric chains should provide significant dispersibility and compatibilization for extruded nanocomposites. Rheological analysis showed better PEO adsorption for PEG-grafted nanocrystals than pristine CN. Results from AFM and SEM revealed homogeneous dispersion and good compatibility of modified nanocrystals in PS matrix. Finally, the thermal, mechanical, and barrier properties of ensuing nanocomposites have been investigated to study the effect of physically and/or chemically modified nanocrystals. © 2013 American Chemical Society.


Lin N.,Grenoble Institute of Technology | Dufresne A.,Grenoble Institute of Technology
Nanoscale | Year: 2014

The process of sulfuric acid-hydrolysis of cellulose fibers for the preparation of cellulose nanocrystals (CNs) includes an esterification reaction between acid and cellulose molecules, which induces the covalent coupling of sulfate groups on the surface of prepared CNs. Negatively charged sulfate groups play an important role in both surface chemistry and physical properties of CNs. This study explored the strategy of introducing a gradient of sulfate groups on the surface of CNs, and further investigated the effect of the sulfation degree on surface chemistry, morphology, dimensions, and physical properties of different CN samples. Based on the discussion of their surface chemistry, the selection of different cross-section models was reported to significantly affect the calculation of the degree of substitution of sulfate groups on CNs. A new ellipsoid cross-section model was proposed on the basis of AFM observations. The effect of sulfate groups on crystal properties and thermal stability was discussed and validated, and the birefringence behavior of nanocrystal suspensions was observed. This journal is © the Partner Organisations 2014.

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