11,653 research outputs found
Complementary use of TEM and APT for the investigation of steels nanostructured by severe plastic deformation
The properties of bulk nanostructured materials are often controlled by
atomic scale features like segregation along defects or composition gradients.
Here we discuss about the complimentary use of TEM and APT to obtain a full
description of nanostructures. The advantages and limitations of both
techniques are highlighted on the basis of experimental data collected in
severely deformed steels with a special emphasis on carbon spatial
distribution
Technological potential of logistics service providers and the relationship dynamics.
Notre papier porte sur plusieurs rĂ©sultats d'une enquĂȘte effectuĂ©e auprĂšs des prestataires logistiques français. L'idĂ©e dĂ©fendue est que l'effort technologique des prestataires de services logistiques contribue Ă la performance de la relation et plus gĂ©nĂ©ralement de la chaĂźne logistique dans sa globalitĂ©. Etre innovant semble constituer un indicateur d'autonomie et de capacitĂ© Ă copiloter les flux. L'effort technologique apparaĂźt ainsi comme une trajectoire stratĂ©gique de diffĂ©renciation pertinente pour les prestataires logistiques.logistic, service providers
Nanostructure and properties of a Cu-Cr composite processed by severe plastic deformation
A Cu-Cr composite was processed by severe plastic deformation to investigate
the role of interphase boundaries on the grain size reduction mechanisms. The
as-deformed material exhibits a grain size of only 20nm. This gives rise to a
dramatic increase of the hardness. Some deformation induced Cu super saturated
solid solutions were clearly exhibited and it is shown that they decrease the
hardness. The formation of such supersaturated solid solution and their
influence on the mechanical properties are discussed
Mechanical alloying of Cu and Fe induced by severe plastic deformation of a Cu-Fe composite
A filamentary composite elaborated by cold drawing was processed by High
Pressure Torsion (HPT). The nanostructure resulting from this severe plastic
deformation (SPD) was investigated thanks to scanning electron microscopy,
transmission electron microscopy, X-ray diffraction and 3D atom probe. Although
the mutual solubility of Cu and Fe is extremely low at room temperature in
equilibrium conditions, it is shown that nanoscaled Fe clusters dissolve in the
Cu matrix. The non-equilibrium copper supersaturated solid solutions contain up
to 20at.% Fe. The driving force of the dissolution is attributed to capillary
pressures and mechanisms which could enhanced the atomic mobility during HPT
are discussed. We conclude that the interdiffusion is the result of a dramatic
increase of the vacancy concentration during SPD.Comment: 20 page
Chemical behavior of tungstate solutions. Part 1. A spectroscopic survey of the species involved
This study is focused on the composition and the evolution of tungstate ions solutions as a function of pH and increasing concentrations. The Raman analysis showed that, during the titration of the tungstate solutions, WO4 2â, HWO4 â ions and probably W2O7 2â, HW2O7 2â and H2W2O7 solvated species could exist in aqueous solutions. For diluted solutions, additions of a strong acid does not cause any precipitation, whereas the formation of the unstable solid tungstic acid (H2WO4 or WO3·H2O) could occur in concentrated solutions
Secure Silicon: Towards Virtual Prototyping
Evaluating security vulnerabilities of software implementations at design step is of primary
importance for applications developers, while it has received litte attention from scientific
communauty. In this paper, we describe virtual prototyping of an implementation of
Elliptic curve cryptography (ECC), aiming to make it secure against first-order horizontal
and vertical side-channel attacks (SCAs). Reproducing information leakage as close to
reality as possible requires bit- and clock-cycle accuracy, we got with Mentor Graphics
Modelsim tool, simulating the execution of the ECC software implementations on PULPino,
an open-source 32-bit microcontroller based on the recently released RISC-V instruction
set architecture. For each clock cycle, we compute the number of bit toggles into
microcontroller's registers, an image of the power consumption, and watch the program
counter to identify the assembly instruction executed, then the corresponding C function.
We first start with a naive double-and-add implementation relying on cryptographic
primitives of the mbed TLS library, formerly PolarSSL before acquisition by ARM. The
virtual analysis pinpoints differences in the way the double function on one side and the
add function on the other side manage variables and internal operations, which can be used
for horizontal SCAs. We propose some modifications of the C code, hence independent of
the considered microcontroller, with an overhead extremely small compared to that of the
double-and-add-always countermeasure. Then, we reiterate analyses, still for the mbed
TLS library, but using the regular Montgomery ladder version, most used in practice as
more efficient
Decomposition process in a FeAuPd alloy nanostructured by severe plastic deformation
The decomposition process mechanisms have been investigated in a Fe50Au25Pd25
(at.%) alloy processed by severe plastic deformation. Phases were characterized
by X-ray diffraction and microstructures were observed using transmission
electron microscopy. In the coarse grain alloy homogenized and aged at , the bcc \alpha-Fe and fcc AuPd phases nucleate in the fcc
supersaturated solid solution and grow by a discontinuous precipitation process
resulting in a typical lamellar structure. The grain size of the homogenized
FeAuPd alloy was reduced in a range of 50 to 100nm by high pressure torsion.
Aging at this nanostructure leads to the decomposition
of the solid solution into an equi-axed microstructure. The grain growth is
very limited during aging and the grain size remains under 100nm. The
combination of two phases with different crystallographic structures (bcc
\alpha-Fe and fcc AuPd) and of the nanoscaled grain size gives rise to a
significant hardening of the allo
INAUT, a Controlled Language for the French Coast Pilot Books Instructions nautiques
We describe INAUT, a controlled natural language dedicated to collaborative
update of a knowledge base on maritime navigation and to automatic generation
of coast pilot books (Instructions nautiques) of the French National
Hydrographic and Oceanographic Service SHOM. INAUT is based on French language
and abundantly uses georeferenced entities. After describing the structure of
the overall system, giving details on the language and on its generation, and
discussing the three major applications of INAUT (document production,
interaction with ENCs and collaborative updates of the knowledge base), we
conclude with future extensions and open problems.Comment: 10 pages, 3 figures, accepted for publication at Fourth Workshop on
Controlled Natural Language (CNL 2014), 20-22 August 2014, Galway, Irelan
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