5,057 research outputs found
Catalytic dehydration of glycerol to acrolein: catalysts and processes
The valorization of glycerol has been widely studied notably due to the oversupply of the latter from biodiesel production. Among the different upgrading reactions, dehydration to acrolein is of high interest due to the importance of acrolein as an intermediate for polymer industry (via acrylic acid) and for feed additive (synthon for DL-methionine). It is known that acrolein can be obtained by glycerol catalytic dehydration over acid catalysts. Zeolites and heteropolyacid catalysts are initially highly active, but deactivate rapidly with time on stream by coking, whilst mixed metal oxides are more stable catalytic systems but less selective and in addition they require an activation period.
In this talk, the strategy we followed is described. It consisted in a parallel approach in which we developed supported heteropolyacid-based catalysts with increased stability and acrolein selectivity by using a ZrO2-grafted SBA-15 playing the role of the support for silico-tungstic acid active phase, as well as a new concept based on a two zones fluidized bed reactor (TZFBR) to tackle the unavoidable deactivation issue of the HPA catalysts. This type of reactor comprises â in one single capacity â reaction and regeneration zones.
In the second part of the lecture the REALCAT platform was introduced. REALCAT (French acronym standing for âAdvanced High-Throughput Technologies Platform for Biorefineries Catalysts Designâ) is an highly integrated platform devoted to the acceleration of innovation in all the fields of industrial catalysis with an emphasis on emergent biorefinery catalytic processes. In this extremely competitive field, REALCAT consists in a versatile High-Throughput Technologies (HTT) platform devoted to innovation in heterogeneous, homogeneous or biocatalysts AND their combinations under the ultra-efficient very novel concept of hybrid catalysis.Universidad de MĂĄlaga. Campus de Excelencia Internacional AndalucĂa Tec
Competition between shear banding and wall slip in wormlike micelles
The interplay between shear band (SB) formation and boundary conditions (BC)
is investigated in wormlike micellar systems (CPyCl--NaSal) using ultrasonic
velocimetry coupled to standard rheology in Couette geometry. Time-resolved
velocity profiles are recorded during transient strain-controlled experiments
in smooth and sand-blasted geometries. For stick BC standard SB is observed,
although depending on the degree of micellar entanglement temporal fluctuations
are reported in the highly sheared band. For slip BC wall slip occurs only for
shear rates larger than the start of the stress plateau. At low entanglement,
SB formation is shifted by a constant , while for more
entangled systems SB constantly "nucleate and melt." Micellar orientation
gradients at the walls may account for these original features.Comment: 4 pages, 4 figures, to appear in Phys. Rev. Let
A morphogenetic crop model for sugar-beet (Beta vulgaris L.)
This paper is the instructions for the proceeding of the International
Symposium on Crop. Sugar beet crop models have rarely taken into account the
morphogenetic process generating plant architecture despite the fact that plant
architectural plasticity plays a key role during growth, especially under
stress conditions. The objective of this paper is to develop this approach by
applying the GreenLab model of plant growth to sugar beet and to study the
potential advantages for applicative purposes. Experiments were conducted with
husbandry practices in 2006. The study of sugar beet development, mostly
phytomer appearance, organ expansion and leaf senescence, allowed us to define
a morphogenetic model of sugar beet growth based on GreenLab. It simulates
organogenesis, biomass production and biomass partitioning. The functional
parameters controlling source-sink relationships during plant growth were
estimated from organ and compartment dry masses, measured at seven different
times, for samples of plants. The fitting results are good, which shows that
the introduced framework is adapted to analyse source-sink dynamics and
shoot-root allocation throughout the season. However, this approach still needs
to be fully validated, particularly among seasons
Experimental demonstration of long-distance continuous-variable quantum key distribution
Distributing secret keys with information-theoretic security is arguably one
of the most important achievements of the field of quantum information
processing and communications. The rapid progress in this field has enabled
quantum key distribution (QKD) in real-world conditions and commercial devices
are now readily available. QKD systems based on continuous variables present
the major advantage that they only require standard telecommunication
technology, and in particular, that they do not use photon counters. However,
these systems were considered up till now unsuitable for long-distance
communication. Here, we overcome all previous limitations and demonstrate for
the first time continuous-variable quantum key distribution over 80 km of
optical fibre. The demonstration includes all aspects of a practical scenario,
with real-time generation of secret keys, stable operation in a regular
environment, and use of finite-size data blocks for secret information
computation and key distillation. Our results correspond to an implementation
guaranteeing the strongest level of security for QKD reported to date for such
long distances and pave the way to practical applications of secure quantum
communications
Multiscale modeling of upper mantle plasticity: From single-crystal rheology to multiphase aggregate deformation
We report a first application of an improved second-order (SO) viscoplastic self-consistent model for multiphase aggregates, applied to an olivine + diopside aggregate as analogue for a dry upper mantle peridotite deformed at 10 15 s 1 shear strain rate along a 20-Ma ocean geotherm. Beside known dislocation slip systems, this SO-model version accounts for an isotropic relaxation mechanism representing âdiffusionrelatedâ creep mechanisms in olivine. Slip-system critical resolved shear stress (CRSS) are evaluated in both phases â as functions of P, T, oxygen fugacity (fO2) and strain rate â from previously reported experimental data obtained on single crystals and first-principle calculations coupled with the PeierlsâNabarro model for crystal plasticity; and the isotropic-mechanism dependence on T and P matches that of Si selfdiffusion in olivine, while its relative activity is constrained by reported data. The model reproduces well the olivine and diopside lattice preferred orientations (LPO) produced experimentally and observed in naturally deformed rocks, as well as observed sensitivities of multiphase aggregate strength to the volume fraction of the hard phase (here diopside). It shows a significant weakening of olivine LPO with increasing depth, which results from the combined effects of the P-induced [100]/[001] dislocation-slip transition and the increasing activity with T of âdiffusion-relatedâ creep. This work thus provides a first quantification of the respective effects of [100]/[001] slip transition and diffusion creep on the olivine LPO weakening inducing the seismic anisotropy attenuation observed in the upper mantle
Technologies of Ascription: How Does a Dementia Diagnosis Acquire its Symbolic Power of Exclusion in Later Life?
Amidst the widespread stigma and exclusion attached to dementia in dominant narratives of successful ageing, this article addresses a gap in the scientific literature concerning our understanding of the medicalization of cognitive decline as a natural phenomenon. To this end, it explores how a dementia diagnosis acquires its symbolic power of exclusion in later life through an ethnography of cognitive rehabilitation therapy in two memory clinics in a southern European nation. It argues that this symbolic power of exclusion is locally produced through the meaning making practices of therapists and researchers administering regular cognitive training therapy and exercises to support autonomy. It shows how the different steps involved in rehabilitation play a role in dividing later life by defining and reifying a category of abnormal ageing during the cognitive assessment, and by applying a confrontational approach exposing decline. It shows how this approach generates the position of older adults who can be rehabilitated against those who cannot; the latter representing a âfailedâ ageing in the narrative of successful ageing. This article proposes the adoption of the concept of âtechnologies of ascriptionâ to characterize this process of exclusion through reification and confrontation of âabnormal cognitive decline.â The paper argues that such practices are central to the local production of the symbolic power attached to a dementia diagnosis as well as its capacity to fragment later life. Finally, it argues for the utility of this concept in offering new opportunities for anthropology to characterize exclusion in later life through medicalization
FPGA Implementation of a General Space Vector Approach on a 6-Leg Voltage Source Inverter
A general algorithm of a Space Vector approach is implemented on a 6-leg VSI controlling a PM synchronous machine with three independent phases. In this last case, the necessity of controlling the zero-sequence current motivates the choice of a special family of vectors, different of this one used in Pulse Width Modulation (PWM) intersective strategy and in common Space Vector PWM (SVPWM). To preserve the parallelism of the algorithm and fulfill the execution time constraints, the implementation is made on a Field Programmable Gate Array (FPGA). Comparisons with more classical 2-level and 3-level PWM are provided.Fui8 within the SOFRACI projec
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