Une optimisation en temps de calcul pour la prédiction de zones de couverture radioélectriques

This article presents a method which optimises the computation time for the prediction of a radio coverage, whatever the propagation model used. The principle consists in reducing the number of application points of the propagation model in relation to a classical technique. The proposed method is based on a multi resolution analysis of measured signals carried out around 2 GHz, and on an electromagnetic analysis of the propagation environment. The performances of the method are evaluated in term of reduction in computation time and of accuracy, in comparaison with the classical technique.     

Proof of usage: user-centric consensus for data provision and exchange

Annals of Telecommunications - This paper presents a new consensus algorithm, Proof of Usage (PoU), for the blockchain technology. This consensus is introduced for permissioned (or private)...     

New alginate foams: Box‐Behnken design of their manufacturing; fire retardant and thermal insulating properties

A new method for preparing alginate foams with progressive release of copper in the presence of sodium lauryl sulfate (SLS, foaming agent) has been designed. Copper acts as the ionotropic gelling agent through the reaction of copper carbonate with gluconolactone. The process does not require freeze‐drying contrarily to the conventional method used for preparing macroporous alginate foams. The new materials investigated in this study have remarkable thermal properties, including thermal conductivity lower than 0.041 W m^?1 K^?1 and low heat release (below 2 kJ g^?1), which allows labeling these foams self‐extinguishing materials. An experimental design methodology, based on a Box‐Behnken plan with three parameters and three levels, is successfully used for evaluating the impact of the amounts of alginate, SLS, and copper carbonate on the productivity, apparent density, and shrinking at air‐drying. It yielded an optimization of the process for the manufacturing of light, and stable/rigid insulating and thermally stable materials. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45868.     

Assessment of copper bioavailability and toxicity in vineyard runoff waters by DPASV and algal bioassay

The aim of this study was to assess the toxicity of runoff waters in an agricultural multipollution context through an in-depth assessment of copper bioavailability and toxicity. Runoff waters were screened for major ions, metals and diuron. The potential environmental impact of these runoff waters was evaluated using the conventional 72-h growth inhibition test with the green alga Pseudokirchneriella subcapitata. The results suggested that the toxicity detected in the calcareous vineyard field was due to the presence of diuron, whereas the non-calcareous runoff waters were non-toxic. Chemical speciation modelling by MINEQL revealed that most of the copper present in the non-toxic natural runoff waters was complexed by organic matter. These samples were spiked with copper, and then the toxicity and the electrochemically bioavailable copper fraction were measured. Differential pulse anodic stripping voltammetry (DPASV) was used to detect labile complexes and free copper. This combined approach highlighted the presence of some labile copper complexes in samples reaching the EC10-these could have contributed to the copper toxicity.     

Methodology for developing a high-precision ultrasound flow meter and fluid velocity profile reconstruction

This article reports the methodology used to develop a high-precision ultrasound transit time flow meter dedicated to liquid hydrocarbons. This kind of flow meter is designed for custody transfer applications requiring accuracy better than 0.15% of reading. We focus here on certain specific points to achieve this accuracy. The transit time method needs to estimate accurately the time delay between signals received by a pair of transducers. In this study, we review different ways of estimating this time delay. We also propose a specific configuration of the flow meter paths. In particular, this configuration compensates for the swirl phenomenon, which has a significant impact on the accuracy of the flow meter. We also propose a theoretical parametric profile to reconstruct the fluid velocity profile in order to perform in situ diagnosis of the flow. The parameters of the model are estimated from the measurements of the flow meter. Simulations and experimental results showed that this method provides characterization of the flow in disturbed and undisturbed flow conditions.     

Spatial fluorescence cross-correlation spectroscopy

We present an alternative method for diffusion measurements of fluorescent species in solution by use of confocal microscopy and fluorescence correlation spectroscopy techniques. It consists of making a time and spatial dual correlation in which one detects the fluorescence signals from two nearby separate confocal volumes and cross correlates them. To improve the spatial discrimination between the two confocal volumes we propose filtering of fluorescence photocounts by rejecting the fluorescence background, which corresponds to particles located far from the center of the detection volumes.     

Loss behavior of viscoelastic sandwich structures: A statistical-continuum multi-scale approach

This work presents a multi-scale model of viscoelastic constrained layer damping treatments for vibrating plates/beams. The approach integrates a finite element (FE) model of macro-scale vibrations and a statistical-continuum homogenization model to include effects of micro-scale structure and properties. The statistical-continuum homogenization model makes the micro- to macro-scale transition to approximate the effective behavior of the heterogeneous core by using n-point probability functions. A simple sound transmission model is used to show the effect of material microstructure on the sound transmission loss of the sandwich structure. The damping behavior resulting from the presence of voids and negative stiffness regions in the core material is modeled. This study clearly shows that, it is of high interest to research either material structures or processing techniques which lead to negative stiffness behavior. The results also poignantly show that the proposed multi-scale model yields insight on heterogeneous material behavior leading to increased damping properties and ultimately enhances the ability to design sandwich beam/plates.     

Assessment of olive pomace wastes as flame retardants

Olive pomace (OP) is a lignocellulosic waste from olive oil industry. In order to valorize these wastes as flame retardant (FR) fillers into polymers, OP residues are milled and screened into three different fractions. Two strategies are then investigated. The first one is to modify OP particles by phosphorus molecules using radiation grafting as already done successfully with flax. Nevertheless, pyrolysis combustion flow calorimetry analyses show that the introduction of phosphorus does not promote charring of OP and flame retardancy is not significantly improved whichever the considered fraction. The second strategy is to replace pentaerythritol by OP as char source into well-known FR systems based on ammonium polyphosphate. The incorporation of such system into ethylene-vinyl acetate copolymer leads to satisfying FR performances according to cone calorimeter tests. Moreover, the presence of high amount of extractives into OP such as oleic acid does not appear detrimental. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 47715.     

Hypoxic Conditions Promote the Angiogenic Potential of Human Induced Pluripotent Stem Cell-Derived Extracellular Vesicles

Stem cells secrete paracrine factors including extracellular vesicles (EVs) which can mediate cellular communication and support the regeneration of injured tissues. Reduced oxygen (hypoxia) as a key regulator in development and regeneration may influence cellular communication via EVs. We asked whether hypoxic conditioning during human induced pluripotent stem cell (iPSC) culture effects their EV quantity, quality or EV-based angiogenic potential. We produced iPSC-EVs from large-scale culture-conditioned media at 1%, 5% and 18% air oxygen using tangential flow filtration (TFF), with or without subsequent concentration by ultracentrifugation (TUCF). EVs were quantified by tunable resistive pulse sensing (TRPS), characterized according to MISEV2018 guidelines, and analyzed for angiogenic potential. We observed superior EV recovery by TFF compared to TUCF. We confirmed hypoxia efficacy by HIF-1α stabilization and pimonidazole hypoxyprobe. EV quantity did not differ significantly at different oxygen conditions. Significantly elevated angiogenic potential was observed for iPSC-EVs derived from 1% oxygen culture by TFF or TUCF as compared to EVs obtained at higher oxygen or the corresponding EV-depleted soluble factor fractions. Data thus demonstrate that cell-culture oxygen conditions and mode of EV preparation affect iPSC-EV function. We conclude that selecting appropriate protocols will further improve production of particularly potent iPSC-EV-based therapeutics.