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International audience; Non-intrusive approaches for the construction of computational vademecums face different challenges, especially when a parameter variation affects the physics of the problem considerably. In these situations, classical interpolation becomes inaccurate. Therefore, classical approaches for the construction of an offline computational vademecum, typically by using model reduction techniques, are no longer valid. Such problems are faced in different physical simulations, for example welding path problems, resin transfer molding, or sheet compression molding, among others. In such situations, the interpolation of precomputed solutions at prescribed parameter values (built using either intrusive or non intrusive techniques) generates spurious numerical artifacts. In this work, we propose an alternative interpolation and simulation strategy by using physically-based morphing of spaces. The morphing will transform the uncompatibe physical domains of the problem’s solution into a compatible one, where an interpolation free of artifacts can be performed. Later on, an inverse transformation can be used to push-back the solution. Different relevant examples are illustrated in this work to motivate the use of the proposed method

This paper investigates the role of the regional context with regard to the influence of human capital and knowledge spillovers on SMEs' financial soundness. Our empirical setting is based on a multilevel analysis of panel data, which allows superior treatment of hierarchical data. The analysis is applied to SMEs belonging to the manufacturing sector and operating in four European countries over the period 2010–2015. We find that a combination of individual and regional‐level characteristics explains firm soundness better than individual features alone. Furthermore, we find that a high local educational level and knowledge spillovers improve firm soundness and that their effects vary according to the regional level of knowledge. These results are confirmed by several robustness tests. Este articulo investiga el papel del contexto regional en relacion a la influencia de los spillovers de conocimiento y de capital humano sobre la solidez financiera de las PYMES. La configuracion empirica se basa en un analisis multinivel de datos de panel, ya que permite un mejor tratamiento de datos jerarquicos. El analisis se aplico a PYMES del sector manufacturero y que operaban en cuatro paises europeos en el periodo 2010‐2015. Se encontro que una combinacion de caracteristicas a nivel individual y regional explica mejor la solidez de las empresas que las caracteristicas individuales por si solas. Ademas, se observa que un alto nivel educativo local y los spillovers de conocimiento mejoran la solidez de las empresas y que sus efectos varian segun el nivel regional de conocimientos. Estos resultados se pudieron confirmar mediante varias pruebas de robustez. 本稿では、中小企業の財務健全性に対する人材と知識のスピルオーバーの影響に関する地域コンテキストの役割を検討する。本研究の実証セッティングはパネルデータのマルチレベル分析に基づくものであり、これによって階層データの優良な処理が可能になる。2010~2015年の期間で、欧州の4つの国で稼働している製造業の中小企業を対象に分析を行う。企業個別の特性だけでなく、それと地域レベルの特性を組み合わせた方が、企業の健全性がよく説明されることがわかる。さらに、地域の教育レベルの高さと知識スピルオーバーが企業の健全性を高めること、また知識スピルオーバーの影響は地域の知識レベルによって異なることが考えられる。この結果は、複数の検定により頑健性が確認された。

Accurate experimental characterization of longitudinal vortices induced by rectangular winglets is necessary to develop and validate numerical models that can predict these flows. For this aim, an experimental investigation is conducted to examine the characteristics of longitudinal vortices generated downstream rectangular winglets in fully developed turbulent channel flow. A row of rectangular winglet pairs is implemented in a parallel plate flow. Stereoscopic Particle Image Velocimetry (SPIV) is used to harvest three-dimensional (3D) instantaneous velocity fields for a Re = 4400 based on the channel’s hydraulic diameter and mean flow velocity. 3D velocity components, velocity streamlines, topologies of Γ2 function and normalized turbulent kinetic energy downstream the winglets are analyzed. It is shown that the flow properties are disturbed, and a main vortex pair is generated in addition to induced vortices downstream the rectangular winglets. Moreover, this work provides an SPIV benchmark of the complex flow developing downstream rectangular winglet pairs, where this configuration has been widley studied using numerical simulations.

Vortex generators (VG) are widely used in enhancing the heat transfer coefficients in heat exchangers due to the development of longitudinal and transverse vortices. Therefore, understanding the development of these vortices has a high importance for the design and optimization of heat exchangers. When using numerical simulations, the choice of an appropriate turbulence model that can better predict the flow structure downstream a VG is fundamental. In the present study, three-dimensional numerical simulations, with two different commonly used eddy viscosity turbulence models, are performed for channel flow fitted with rectangular-winglet pairs (RWP) vortex generators. The numerical results are compared to experimental data obtained by stereoscopic particle image velocimetry (SPIV). The shear-stress transport (SST) κ-ω model and the re-normalization-group (RNG) κ-e model are used for modeling turbulence. Validation is conducted by comparing the flow structure topology and velocity field obtained from numerical simulations to those obtained using the SPIV method. It is found that the SST κ-ω model is better than the RNG κ-e turbulence model in predicting the flow characteristics downstream the RWP.

Many efforts have been deployed by the IR community to extend free-text query processing toward semi-structured XML search. Most methods rely on the concept of Lowest Comment Ancestor (LCA) between two or multiple structural nodes to identify the most specific XML elements containing query keywords posted by the user. Yet, few of the existing approaches consider XML semantics, and the methods that process semantics generally rely on computationally expensive word sense disambiguation (WSD) techniques, or apply semantic analysis in one stage only: performing query relaxation/refinement over the bag of words retrieval model, to reduce processing time. In this paper, we describe the building blocks of a new approach for XML keyword search aiming to solve the limitations mentioned above. Our solution first transforms the XML document collection (offline) and the keyword query (on-the-fly) into meaningful semantic representations using context-based and global disambiguation methods, specially designed to allow almost linear computation efficiency. Consequently, the semantically augmented XML data tree is processed for structural node clustering, based on semantic query concepts (i.e., key-concepts), in order to identify and rank candidate answer sub-trees containing related occurrences of query key-concepts. Preliminary experiments highlight the quality and potential of our approach.

A nonparametric method assessing the error and variability margins in solutions depicted in a separated form using experimental results is illustrated in this work. The method assess the total variability of the solution including the modeling error and the truncation error when experimental results are available. The illustrated method is based on the use of the PGD separated form solutions, enriched by transforming a part of the PGD basis vectors into probabilistic one. The constructed probabilistic vectors are restricted to the physical solution’s Stiefel manifold. The result is a real-time parametric PGD solution enhanced with the solution variability and the confidence intervals.

International audience; This work aims at proposing a new procedure for parametric problems whose separated representation has been considered difficult, or whose SVD compression impacted the results in terms of performance and accuracy. The proposed technique achieves a fully separated representation for layered domains with interfaces exhibiting waviness or – more generally – deviating from planar surfaces, parallel to the coordinate plane. This will make possible a simple separated representation, equivalent to others, already analyzed in some of our former works. To prove the potentialities of the proposed approach, two benchmarks will be addressed, one of them involving an efficient space–time separated representation achieved by considering the same rationale.

International audience; In this work we develop a void filling and void motion dynamics model using volatile pressure and squeeze flow during tape placement process. The void motion and filling are simulated using a non-local model where their presence is reflected in the global macroscale behavior. Local pressure gradients during compression do play a critical role in void dynamics, and hence the need for a non-local model. Deriving a non-local model accounting for all the void motion and dynamics entails a prohibitive number of degrees of freedom, leading to unrealistic computation times with classical solution techniques. Hence, Proper Generalized Decomposition – PGD – is used to solve the aforementioned model. In fact, PGD circumvents the curse of dimensionality by using separated representation of the space coordinates. For example, a 2D problem can be solved as a sequence of 1D problems to find the 2D solution. The non-local model solution sheds light on the fundamental of the void dynamics including their pressure variation, motion and closure mechanisms. Finally, a post treatment of the transient compression of the voids is used to derive conclusions regarding the physics of the void dynamics.

International audience; Microwave (MW) technology relies on volumetric heating, where thermal energy is induced from an electromagnetic field. Nowadays, the main drawback of this technology is that the complex physics involved in the conversion of electromagnetic energy into thermal energy is not entirely understood and controlled. The main objective of this work is to model, simulate and validate the interactions of microwaves with a composite laminate consisting of a stack of unidirectional layers composed of a resin matrix and carbon fibers, to predict its heating. Once validated, this simulation tool will serve to predict, control and optimize composites forming processes.

International audience; The purpose of this study was to investigate the relationships between skeletal muscle index (SMI) and bone variables in a group of young adults. Three hundred and thirty-five young adults (129 men and 206 women) whose ages ranged from 18 to 35 yr voluntarily participated in this study. Weight and height were measured, and body mass index (BMI) was calculated. Body composition, bone mineral content (BMC), bone mineral density (BMD), geometric indices of hip bone strength and trabecular bone score (TBS) were determined for each individual by Dual-energy X-ray absorptiometry (DXA). Appendicular skeletal mass (ASM, in kg) was calculated by summing the muscle masses of the 4 limbs, assuming that all nonfat and nonebone mass is skeletal muscle. Skeletal muscle index (SMI) was defined as ASM/height². In young men, SMI was positively correlated to WB BMC (r = 0.63; p < 0.001), WB BMD (r = 0.53; p < 0.001), L1-L4 BMC (r = 0.33; p < 0.001), L1-L4 BMD (r = 0.30; p < 0.001), L1-L4 TBS (r = 0.26; p < 0.01), TH BMC (r = 0.61; p < 0.001), TH BMD (r = 0.46; p < 0.001), FN BMC (r = 0.51; p < 0.001), FN BMD (r = 0.46; p < 0.001), FN cross-sectional area (CSA) (r = 0.56; p < 0.001), FN cross-sectional moment of inertia (CSMI) (r = 0.52; p < 0.001) and FN section modulus (Z) (r = 0.54; p < 0.001) but negatively correlated to FN strength index (SI) (r = -0.24; p < 0.01). In young women, SMI was positively correlated to WB BMC (r = 0.61; p < 0.001), WB BMD (r = 0.60; p < 0.001), L1-L4 BMC (r = 0.35; p < 0.001), L1-L4 BMD (r = 0.33; p < 0.001), L1-L4 TBS (r = 0.29; p < 0.001), TH BMC (r = 0.61; p < 0.001), TH BMD (r = 0.53; p < 0.001), FN BMC (r = 0.45; p < 0.001), FN BMD (r = 0.49; p < 0.001), FN CSA (r = 0.60; p < 0.001), FN CSMI (r = 0.52; p < 0.001), and FN Z (r = 0.40; p < 0.001) but negatively correlated to FN SI (r = -0.20; p < 0.01). The current study suggests that SMI is a positive determinant of bone mineral density and geometric indices of hip bone strength in young adults.

Arsenic is amongst the most hazardous heavy metals released into the environment by natural or human-induced sources. A known carcinogen and irritant, its trivalent and pentavalent forms are the most common in aqueous media rendering their onsite monitoring and removal crucial. In this work, different adsorbents based on iron oxide nanoparticles (Fe­3O4 NPs) coated with (3-aminopropyl)triethoxysilane (APTES) were prepared. The nanoparticles were then functionalized with one of the three nucleobase derivatives: adenine hydrazide (AH), guanine hydrazide (GH) or uracil hydrazide (UH). The successful functionalization of the nanoparticles was confirmed using Fourier transform infrared spectroscopy. Boron-doped diamond electrodes were modified using the different functionalized nanoparticles, and the interaction of the nucleobases with trivalent arsenic ions was assessed using square wave voltammetry, the adsorption efficiency being extracted from the decrease of the nucleobase peak maximum intensity. The electrochemical evaluation of adsorption isotherms showed that the Langmuir model was a better fit compared to Freundlich, and that the adsorption capacity increased in the following order: AH < UH < GH. Furthermore, it was shown that the adsorption follows a pseudo-second order kinetic model implying the involvement of chemisorption in the process. The electrochemical detection of arsenic utilizing the magnetic nanoparticles functionalized with guanine hydrazide showed a better analytical performance compared to adenine and uracil hydrazide, with a sensitivity of 1.92 µA.µg-1.L and limit of detection of 1.6 µg/L.

A novel Model Order Reduction (MOR) technique is developed to compute high-dimensional parametric solutions for electromagnetic fields in synchronous machines. Specifically, the intrusive version of the Proper Generalized Decomposition (PGD) is employed to simulate a Permanent-Magnet Synchronous Motor (PMSM). The result is a virtual chart allowing real-time evaluation of the magnetic vector potential as a function of the operation point of the motor, or even as a function of constructive parameters, such as the remanent flux in permanent magnets. Currently, these solutions are highly demanded by the industry, especially with the recent developments in the Electric Vehicle (EV). In this framework, standard discretization techniques require highly time-consuming simulations when analyzing, for instance, the noise and vibration in electric motors. The proposed approach is able to construct a virtual chart within a few minutes of off-line simulation, thanks to the use of a fully separated representation in which the solution is written from a series of functions of the space and parameters coordinates, with full space separation made possible by the use of an adapted geometrical mapping. Finally, excellent performances are reported when comparing the reduced-order model with the more standard and computationally costly Finite Element solutions. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Microwave (MW) technology relies on volumetric heating, where thermal energy is induced from an electromagnetic field. Nowadays, the main drawback of this technology is that the complex physics involved in the conversion of electromagnetic energy into thermal energy is not entirely understood and controlled. The main objective of this work is to model, simulate and validate the interactions of microwaves with a composite laminate consisting of a stack of unidirectional layers composed of a resin matrix and carbon fibers, to predict its heating. Once validated, this simulation tool will serve to predict, control and optimize composites forming processes. This work was partially done in the framework of the Simutool H2020 Project. The authors would like to thank Jasmin Stein from TWI (UK) for the thermal measurements done in the microwave oven, and Remi Chauveau from Loiretech (France) for the tooling and experimental set up.

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International audience; Most heavy metal ions are known to be toxic and carcinogenic when present in high amounts. Thus, rapid and reliable on-site detection of these ions is crucial. Voltammetry is a highly sensitive electrochemical method that has been widely used for heavy metal detection offering the advantages of sensitivity and rapidity. On the other hand, nanoparticles offer the advantages of high surface area and high selectivity. Thus, this review aims to highlight the application of metallic and metallic oxide nanoparticles for the voltammetric detection of heavy metals. The nanoparticles used were either applied solely on the electrode or as modifiers with various materials. In all cases, the synthesized devices showed an enhanced analytical performance, such that the limits of detection were lowered and the sensitivities were increased as compared to voltammetric systems not using nanoparticles. Moreover, the applicability of some of these systems was investigated in real samples.

Promotion of both market fairness and efficiency has long been a goal of securities market regulators worldwide. While previous studies mostly focused on market efficiency, our paper proposes tools to improve market fairness. We define market fairness as the ability of a market structure and its regulatory framework to guarantee unimpeded competition while curbing excessive speculation and market manipulation. Such behaviors undermine the quality of financial markets in the sense that they cause volatility and lead to instability. To encourage value generation and improve market quality, we advance a graduated Non-Value-Added Tax. The proposed tax is implemented in a simulation-based model whereby a profitable transaction is taxed at the higher rate if it does not enhance efficiency measured by deviation from fundamentals. When an agent locks in profit not supported by fundamentals but driven by trend-following strategies, the generated profit is taxed at graduate rates under the Non-Value-Added Tax regime. Unlike existing Financial Transaction Taxes, the Non-Value-Added Tax is levied on profit and not on price. More concretely, our findings show that this tool encourages profitable trades that add-value to the market and discourages valueless profit making. It significantly curtails volatility, and prevents the occurrence of extreme market events like bubbles and crashes.

Neonates, especially preterm and sick infants, face difficulty controlling their body temperature. Thus, they are nursed inside incubators in order to improve their hygrothermal condition and monitor their body temperature as well as other vital signs. The complex processes of heat and mass transfer between the neonates and the surrounding air and surfaces are the key concerns essential to their growth and survival. Several methods are used in order to better understand the physical phenomena of dry and latent heat losses from neonates and the body-environment interaction occurring during transient clinical processes and in thermoneutrality, which is the optimum thermal environment for neonates nursed inside incubators. These methods can be classified into three main categories: bioheat modeling, computational fluid dynamics and experimental studies. The objective of these methods is to analyze the effect of different ambient conditions, such as air temperature and humidity, incubator wall temperatures and air flow, on the dry heat losses by convection, conduction and radiation and on latent heat losses due to skin evaporation and respiratory process. The main indicators are the metabolic heat generation, skin and core body temperatures. Moreover, based on these methods, different techniques are proposed to enhance the incubator hygrothermal conditions. All these issues are reviewed in this paper and some future recommendations are drawn.

International audience; Phase Change Materials (PCM) have been a emerging research topic for the last few years. However, the lack of detailed and precise information regarding their thermophysical properties is a major concern for researchers. The current paper presents a simple method to determine the specific heat (Cp), thermal conductivity (K) and melting temperature (Tm) of a PCM using a novel low cost device. Compared to the conventional existing methods such as Differential Scanning Calorimetry (DSC), T-history, panel test and simple thermal analysis, this new method grants the following features: simplicity and ease of manufacturing and the ability to measure the thermophysical properties of heterogeneous PCMs samples without a reference material. Using this novel device, the thermophysical properties of the sodium sulfate decahydrate were measured and good agreement is obtained with values collected from the open literature using other devices.

The Riemannian product $\mathbb M_1(c_1) \times \mathbb M_2(c_2)$, where $\mathbb M_i(c_i)$ denotes the $2$-dimensional space form of constant sectional curvature $c_i \in \mathbb R$, has two different Spin$^c$ structures carrying each a parallel spinor. The restriction of these two parallel spinor fields to a $3$-dimensional hypersurface $M$ characterizes the isometric immersion of $M$ into $\mathbb M_1(c_1) \times \mathbb M_2(c_2)$. As an application, we prove that totally umbilical hypersurfaces of $\mathbb M_1(c_1) \times \mathbb M_1(c_1)$ and totally umbilical hypersurfaces of $\mathbb M_1(c_1) \times \mathbb M_2(c_2)$ ($c_1 \neq c_2$) having a local structure product, are of constant mean curvature., Comment: arXiv admin note: text overlap with arXiv:1203.3034

International audience; In SMC processes, a charge of a composite material, which typically consists of a matrix composed of an unsaturated polyester or vinylester, reinforced with chopped glass fibres or carbon fi bre bundles and fillers, is placed on the bottom half of the preheated mould. The charge usually covers 30 to 90% of the total area. The upper half of the mould is closed rapidly at a speed of about 40 mm/s. This rapid movement causes the charge to flow inside the cavity. The reinforcing fibres are carried by the resin and experience a change of confi guration during the flow. This strongly influences the mechanical properties of the final part. Several issues compromises its efficient numerical simulation, among them: (i) the modeling of flow kinematics able to induce eventual fibres/resin segregation, (ii) the con ned fibres orientation evolution and its accurate prediction, (iii) local dilution effects, (iv) flow bifurcation at junctions and its impact on the fibres orientation state, (v) charge / mould contact and (vi) parametric solutions involving non-interpolative fields.The present paper reports advanced modeling and simulation techniques for circumventing, or at least alleviating, the just referred difficulties.

National audience; Local analysis and visualization of convective heat transfer is fundamental for many engineering applications. In fact, the correlation between the flow structure and the transport of heat by advection and diffusion is crucial for designing and optimizing devices undergoing heat transfer, such as heat exchangers. The field synergy principle has been used for more than two decades in order to analyze and enhance the convective heat transfer in different applications. In this paper, the validity of the field synergy principle in elliptic flows is tested for both laminar and turbulent flow regimes. For this end, the flow past a backward facing step is considered for a wide range of Reynolds numbers based on the step height ranging from 36 to 36,000. It is shown that the synergy angle and synergy number both fail to represent the local physics of heat transfer process near the step. This is caused by the assumption of negligible molecular and turbulent thermal diffusivities in this principle. In this paper, it is shown that these diffusivities play a crucial role in heat transfer in elliptic flows and cannot be ignored. Moreover, a global analysis shows that the field synergy number could be used to predict the Nusselt number variation if the elliptic region in the flow is small however, the synergy angle fails here also to characterize the variation in Nusselt number.

National audience; Cross-linked polyethylene (XLPE) is a thermoset polymeric material extensively used in the industry, including in firefighting systems, hot water and sanitary piping, and for the insulation of electric cables. The cross-linking of polyethylene increases its performance while reducing its recyclability. A recent approach considers processing XLPE waste materials in the form of small flakes to partially replace natural aggregates in concrete mixtures. Ongoing experimental and numerical studies addressing the homogenized mechanical properties of such composite mixtures are showing their feasibility. Despite a decreased stiffness and strength due to the presence of XLPE inclusions (which are typically weaker than traditional aggregates) the modified concrete mixtures can still maintain working structural properties. In this vein, it is also interesting to characterize the role of XLPE inclusions in improving the thermal insulation of XLPE-modified concretes. A virtual concrete wall is thus modeled numerically, in 2D at the mesoscale, to study the statistical effect of varying the volume fractions of XLPE inclusions, and aggregates, on the homogenized thermal conductivity of the modified concrete. The equivalent thermal conductivity of the wall k eq typically drops as more aggregates are replaced by XLPE inclusions, thus achieving better thermal insulation. The dependence of k eq on the area fraction of XLPE is roughly linear, while the statistical variability is very low. Nomenclature a f area fraction of inclusions d size of aggregate's trace in the domain, m D aggregate diameter, m k thermal conductivity, W/ (m. • C) L length of inclusions, m l x wall/domain thickness (x-direction), m l y Wall/domain height (y-direction), m m mass, kg q heat flux, W/m 2 T temperature, • C x position through wall/domain thickness, m y position through wall/domain height, m Greek symbols α cross-section/trace factor of aggregates Ω 2D wall domain Subscripts − (.) aggregate traditional aggregates − (.) Lef t left wall/domain boundary − (.) mortar mortar matrix − (.) Right right wall/domain boundary − (.) XLP E

National audience; Electromagnetic forcing could be used to produce streamwise vortices in order to enhance the heat and mass transfer processes in ducts and pipes. In our current study we take this novel method to a more practical use, to suggest a Magneto hydrodynamic heat exchanger in which several transverse Lorentz forces are arranged along the streamwise direction to produce secondary flow structures and enhance mixing of hot fluid particles near the wall with cold fluid particles near the center. The Reynolds number based on the mean flow velocity and hydraulic diameter is taken 1000. The flow structures, the local heat transfer and the thermal performances are quantitatively analyzed to show the effectiveness of this concept. Increases by more than 100% in the global Nusselt number and the thermal performance were detected. Several configurations of forcings were tested, where it was found that the increase in local and global Nusselt is more efficient with subsequent forces of the same direction, rather than changing directions. Nomenclature A overall area of heat transfer, m 2 B magnetic field, T c heat capacity of the fluid, J/kgK F Lorentz force, N/m 3 GCI Grid convergence index h convective heat transfer coefficient, W/m 2 K J current density, A/m 3 k bulk fluid thermal conductivity, W/mK N u global Nusselt number N u z local Nusselt number p c apparent order of converge q overall rate of heat transfer, W S exchange area, m 2 T temperature, K ∆T lm log mean temperature difference, K u velocity vector field, m/s Greek symbols ρ density, kg/m 3 µ dynamic viscosity, Pa.s φ electric field scalar potential, V σ electric conductivity of the fluid, S

International audience; Preterm infants face difficulties in maintaining their body temperature due to low metabolic rates of heat generation. Therefore, using incubators and radiant warmers is crucial for their comfort and health. The objective of the present work is to analyze the heat transfer processes for a preterm infant nursed in a simplified incubator under two different operating conditions: in the first one a classical simple incubator is considered and in the second case radiant heaters are used. This is achieved by using ANSYS Fluent 19.0 which his based on the finite volume method to discretize the Navier-Stokes, energy and radiation transfer equations. Conduction, convection and radiation heat transfer modes are modelled in the simulations and coupled to empirical correlations for metabolic heat generation and evaporative heat losses. The different incubator scenarios considered here are compared in terms of convection and radiation heat losses and skin temperature to access the thermal comfort of the preterm infant.

Biphasic soft materials are challenging to model by nature. Ongoing efforts are targeting their effective modeling and simulation. This work uses experimental atomic force nanoindentation of thick hydrogels to identify the indentation forces are a function of the indentation depth. Later on, the atomic force microscopy results are used in a GENERIC general equation for non-equilibrium reversible&ndash, irreversible coupling (GENERIC) formalism to identify the best model conserving basic thermodynamic laws. The data-driven GENERIC analysis identifies the material behavior with high fidelity for both data fitting and prediction.

International audience; The present work aims at proposing a new methodology for learning reduced models from a small amount of data. It is based on the fact that discrete models, or their transfer function counterparts, have a low rank and then they can be expressed very efficiently using few terms of a tensor decomposition. An efficient procedure is proposed as well as a way for extending it to nonlinear settings while keeping limited the impact of data noise. The proposed methodology is then validated by considering a nonlinear elastic problem and constructing the model relating tractions and displacements at the observation points.

International audience; The study of recommender systems is essential nowadays due to its great effect on businesses and customer satisfaction. Different active learning strategies were previously developed to gain ratings from the users on specific items, and this enables the system to have more information and consequently make more accurate recommendations. In previous studies, these strategies were evaluated using a different selection of metrics in each work, and the experimentations were done on different datasets. In this paper, we solve these weaknesses by comparing the main ten non-personalized strategies on a fair ground, by simulating them against two datasets and using seven of the mostly agreed upon metrics. This gives more trust and less biased results when comparing their performances. Also, the analysis of the computation time and the elicitation efficiency is added.

International audience; This paper analyzes the ability of different machine learning techniques, able to operate in the low-data limit, for constructing the model linking material and process parameters with the properties and performances of parts obtained by reactive polymer extrusion. The use of data-driven approaches is justified by the absence of reliable modeling and simulation approaches able to predict induced properties in those complex processes. The experimental part of this work is based on the in situ synthesis of a thermoset (TS) phase during the mixing step with a thermoplastic polypropylene (PP) phase in a twin-screw extruder. Three reactive epoxy/amine systems have been considered and anhydride maleic grafted polypropylene (PP-g-MA) has been used as compatibilizer. The final objective is to define the appropriate processing conditions in terms of improving the mechanical properties of these new PP materials by reactive extrusion.

International audience; Mixing in laminar flow regimes is crucial for many engineering applications in which highly viscous and fragile fluids are used. Moreover, the compactness of laminar mixers is a great challenge due to the large mixing time required to obtain the desired homogeneity. The "Split And Recombine" (SAR) static mixers are a promising solution for this challenge. This type of mixers consists of a network of separated and then recombined channels in which two fluids are introduced separately and mixed by a multi-lamination process. The SAR static mixers perform a series of baker's transforms on the concentration profile enhancing thus the mixing process at very low Reynolds numbers. In the present study, numerical simulations are carried out to analyze the mixing process in a new topology of SAR mixer with double separation and recombination in order to increase the lateral gradients and destroy the concentration profile faster. The new geometry proposed here is compared to two SAR configurations widely studied in the open literature namely the Gray and the Chen SAR configurations. The results show a good enhancement of the mixing process in the new double SAR configuration with decrease in the power dissipation. INTRODUCTION Efficient mixing remains a challenging process in many engineering applications such as food processing

International audience; This article portrays a compact wideband coplanar-fed V-shaped antenna. It has been designed for harvesting energy from wireless local area networks (IEEE 802.11) and other wireless communication systems covering the 2–6 GHz frequency band. The Structure of this antenna comprises a rectangular patch and an isosceles trapezoid. A V-shaped slot is introduced on the rectangular patch in order to perturb the surface current path which contributes to the formation of the wide-band characteristics. A trapezoid is inserted between the coplanar feed and the patch for the purpose of impedance matching and resonance shifting. A parametric study has been carried out to understand the effects of various dimensional parameters and to optimize the performance of the antenna. The measurement results which are in agreement with Ansoft HFSS simulation results, showed an agreeable bandwidth and satisfactory characteristics for omnidirectional radiation.

International audience; Recommender systems have a better performance whenever they have more information about the users. When little to no information is available for a certain user, the system fails to provide them with accurate recommendations, and this is referred to as the cold-start problem. To solve this issue, non- personalized and personalized active learning strategies were proposed, with an aim to obtain some ratings from the new user on specific items. In this paper, we tackle the non-personalized category, we compare the strategies that were previously suggested in the literature, and we propose a new strategy that combines some selected previous strategies. We use the public MovieLens dataset in the experimentations and we use MAE and RMSE to compare the strategies. The results show that our strategy performs better than the individual strategies previously used.

International audience; In this paper, a reconfigurable patch antenna design operating at 868MHz for Low Power Wide Area Network (LoRa), 1.58 GHz for Global Positioning System (GPS) and 2.4 GHz for Bluetooth is presented. The design is reconfigurable thanks to the integration of a digitally tunable capacitor (DTC). The DTC capacitance changes according to a 5 bits' sequence command. A microcontroller is used to assign the required sequence, and thus leading to frequency reconfiguration. The antenna is a circular patch with a gain that varies from 0.2 dB to 6 dB based on the desired frequency of operation and the reconfiguration state. The antenna is designed for internet of things (IoT) applications.

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Post-seismic investigations repeatedly indicate that structures having frequencies close to foundation soil frequencies exhibit significantly heavier damages (Caracas 1967; Mexico 1985; Pujili, Ecuador 1996; L’Aquila 2009). However, observations of modal frequencies of soils and buildings in a region or within a current seismic risk analysis are not fully considered together, even when past earthquakes have demonstrated that coinciding soil and building frequencies leads to greater damage. The present paper thus focuses on a comprehensive numerical analysis to investigate the effect of coincidence between site and building frequencies. A total of 887 realistic soil profiles are coupled with a set of 141 single-degree-of-freedom elastoplastic oscillators, and their combined (nonlinear) response is computed for both linear and nonlinear soil behaviors, for a large number (60) of synthetic input signals with various PGA levels and frequency contents. The associated damage is quantified on the basis of the maximum displacement as compared to both yield and ultimate post-elastic displacements, according to the RISK-UE project recommendations (Lagomarsino and Giovinazzi in Bull Earthq Eng 4(4):415–443, 2006), and compared with the damage obtained in the case of a similar building located on rock. The correlation between this soil/rock damage increment and a number of simplified mechanical and loading parameters is then analyzed using a neural network approach. The results emphasize the key role played by the building/soil frequency ratio even when both soil and building behave nonlinearly; other important parameters are the PGA level, the soil/rock velocity contrast and the building ductility. A numerical investigation based on simulation of ambient noise for the whole set of 887 profiles also indicates that the amplitude of H/V ratio may be considered as a satisfactory proxy for site amplification when applied to measurements at urban scale. A very easy implementation of this method, using ambient vibration measurements both at ground level and within buildings, is illustrated with an example application for the city of Beirut (Lebanon). Graphical abstract .

International audience

International audience; Aeronautic Certification rules established for the metallic materials are not convenient for the composite structures concerning the resistance against impact. The computer-based design is a new methodology that is thought about to replace the experimental tests. It becomes necessary for numerical methods to be robust and predictive for impact. Three questions are addressed in this study: (i) can a numerical model be \textquotedblleftmechanically intrinsic\textquotedblright to predict damage after impact, (ii) can this model be the same for a lab sample and a large structure, and (iii) can the numerical model be predictive enough to predict the Compression After Impact (CAI)? Three different computational strategies are used and compared: a Cohesive Model (CM), a Continuous Damage Model (CDM) coupling failure modes and damage, and a Mixed Methodology (MM) using the CDM for delamination initiation and the CM for cracks propagation. The first attempts to use the Smooth Particle Hydrodynamics method are presented. Finally, impact on a fuselage is modelled and a numerical two-stage strategy is developed to predict the CAI.

This study characterizes a new mixing process based on chaotic advection for the production of water/oil (w/o) emulsified engine fuel. At low and intermediate Reynolds numbers, in curved pipes, Dean roll-cells induce radial convective mass transfer, a mechanism exploited in the technology of helical static mixers. The succession of bends of alternating curvature planes produces in addition spatially chaotic flow trajectories that enhance the mixing over and above that in the reference helically coiled geometry made of coplanar bends. This feature is assessed in the present work by comparison of the droplet sizes obtained in helical (regular) and alternating (chaotic) static mixers of the same cross section and the same tube length. The coils are assembled from 90 degrees bends, and the chaotic configuration is obtained by turning each bend by +/- 90 degrees with respect to the previous one. To cover a large range of Reynolds numbers [30-350] and capillary numbers [0.1-1], a lipophilic solvent (Butanol) is added to the continuous phase (oil) to decrease the viscosity and a surfactant (Tween 20) is used beyond the critical concentration (covering the whole w/o interface) to decrease the interfacial tension. Drop-size measurements at the exit of the mixer in the chaotic advection configuration show substantial drop-size reduction and tightening in drop-size distribution. Moreover, it is shown that mixing intensification by chaotic advection is almost independent of Reynolds number in the studied range, with a mixing efficiency enhancement around 30%. (C) 2013 Elsevier Ltd. All rights reserved.

Nevertheless the huge amount of numerical and experimental works on non-colloidal suspension flows, most studies in the literature were limited to the dynamics in different geometries like in channels and pipes. To author's knowledge, mixing enhancement quantification and suspension mixing behavior in static mixers has been rarely studied before. In the present contribution, the mixing enhancement in isothermal monodisperse neutrally buoyant non-Brownian suspensions is investigated through transient 3D CFD simulations. It is quantified for suspension Reynolds (ReS) numbers varying between 50 and 150, for spheres’ diameters (dp) between 25 and 400 μm and for initial volume fractions of particles (ϕ) between 0.25 and 0.45. The influences of dp, ReS and ϕ on the overall mixing enhancement and on pressure drop are quantified for a suspension flow in a chaotic and helical separate pipes (static mixers of equal lengths). It is found that for all cases, the chaotic flow configuration has better mixing performances than the helical pipe flow with almost no significant increase in pressure losses. Moreover, good mixing quality is observed in both static mixers (better at larger particles) where the mixing index ranges between 10 and 75% relative to the initial unmixed particles leaving the straight pipe.

International audience; Passive methods are widely used for flow control in engineering processes for heat and mass transfer enhancement. Using flexible vortex generators (FVGs) in such applications in order to destabilize the flow can be thought to achieve higher performances taking advantage of the fluid-structure interaction. In this paper, we discuss the assessment of getting self-sustained large oscillation amplitudes of multiple FVGs from an upstream confined laminar flow. The FVGs are located on the opposite channel walls in alternated positions, separated by a distance equal to their span and inclined in the upstream direction with an angle of 30° with respect to the wall. Five cases are studied which differ by the number of alternating FVGs in the system and investigations are also performed adding two co-planar FVGs upstream. The Reynolds number is held constant with a value of 2000 (based on the hydraulic diameter) for all the cases. The effect of increasing the degree of freedom of the system, on creating a large displacement flapping motion is numerically investigated. The results show that a minimum of three alternating FVGs is needed to produce a self-sustained and periodic flow instability, leading to large FVG displacement when the co-planar FVGs are not present. The introduction of upstream co-planar FVGs destabilizes the flow by producing vortices which act as periodic forces on the downstream FVGs. In this case, large displacement amplitudes are thus observed with two alternating FVGs added downstream. A phenomenon of inverted drafting is observed in all the cases: upstream FVGs display smaller drag force values than the downstream ones. Since the downstream FVGs oscillate in resonance with the incoming flow, motion amplitudes become higher. Moreover, it has been observed that for all the configurations studied here, the FVGs located at the same wall location oscillate in phase with each others and out-of-phase with the ones located on the opposite channel wall.

Resonance period is a key parameter in the seismic design of a structure, thus dynamic parameters of buildings in Beirut (Lebanon) were investigated based on ambient vibration method for risk and vulnerability assessment. Lebanon is facing high seismic hazard due to its major faults, combined to a high seismic risk caused by dense urbanization in addition to the lack of a seismic design code implementation. For this study, ambient vibration recordings have been performed on 330 RC buildings, period parameters extracted and statistically analyzed to identify correlations with physical building parameters (height, horizontal dimensions, age) and site characteristics (rock sites or soft sites). The study shows that (1) the building height or number of floors (N) is the primary statistically robust parameter for the estimation of the fundamental period T; (2) the correlation between T and N is linear and site dependent: T ae N/23 for rock sites and N/18 for soft sites; (3) the measured damping is inversely proportional to the period: the taller the building the lower is the damping; (4) a significant overestimation of the period exists in current building codes. However part of the large discrepancy with building code recommendations may be due to the very low level of loading.

International audience; We extend the Friedrich inequality for the eigenvalues of the Dirac operator on Spin c manifolds with boundary under different boundary conditions. The limiting case is then studied and examples are given.

This paper aims to assess the impact of the envelope airtightness on both heating needs and airflow patterns for the case of a single-detached dwelling as function of the ventilation system. An original numerical approach based on the energy simulation tool TRNSYS coupled to the multi-zone airflow and contaminant transport model COMIS was used to compare the performance of four mechanical ventilation strategies. The impacts of the envelope leakage location (facades and/or ceiling), the zone configuration (one- or multi-zone model), the climatic and wind exposure conditions (exposed or surrounded by obstructions) were also investigated. The results show a significant increase of the heating needs when the air permeability at 4 Pa is increased depending on the climatic conditions. Furthermore, the desired airflow pattern, and hence the dispersion of pollutants from main rooms to service rooms can be significantly disturbed especially in the case of humidity-sensitive ventilation system.

Given a Riemannian spin $$^c$$ manifold whose boundary is endowed with a Riemannian flow, we show that any solution of the basic Dirac equation satisfies an integral inequality depending on geometric quantities, such as the mean curvature and the O’Neill tensor. We then characterize the equality case of the inequality when the ambient manifold is a domain of a Kahler–Einstein manifold or a Riemannian product of a Kahler–Einstein manifold with $$\mathbb R$$ (or with the circle $$\mathbb S^1$$ ).

In this paper, we consider a compact Riemannian manifold whose boundary is endowed with a Riemannian flow. Under a suitable curvature assumption depending on the O'Neill tensor of the flow, we prove that any solution of the basic Dirac equation is the restriction of a parallel spinor field defined on the whole manifold. As a consequence, we show that the flow is a local product. In particular, in the case where solutions of the basic Dirac equation are given by basic Killing spinors, we characterize the geometry of the manifold and the flow., Comment: 22 pages

The complex projective space $\mathbb C P^2$ of complex dimension $2$ has a Spin$^c$ structure carrying K\"ahlerian Killing spinors. The restriction of one of these K\"ahlerian Killing spinors to a surface $M^2$ characterizes the isometric immersion of $M^2$ into $\mathbb C P^2$ if the immersion is either Lagrangian or complex., Comment: 18 pages

Crowdsourcing mobile applications are of increasing importance due to their suitability in providing personalized and better matching replies. The competitive edge of crowdsourcing is twofold; the requestors can achieve better and/or cheaper responses while the crowd contributors can achieve extra money by utilizing their free time or resources. Crowdsourcing location-based services inherit the querying mechanism from their legacy predecessors and this is where the threat lies. In this paper, we are going to show that none of the advanced privacy notions found in the literature except forK-anonymity is suitable for crowdsourced location-based services. In addition, we are going to prove mathematically, using an attack we developed, thatK-anonymity does not satisfy the privacy level needed by such services. To respond to this emerging threat, we will propose a new concept, totally different from existing resource consuming privacy notions, to handle user privacy using Mobile Cloud Computing.

Several vortex generator shapes are used to increase heat and mass transfer in open and internal flows. Here we report a three-dimensional numerical study investigating the effects of longitudinal and transverse vortices on the heat and mass transfer mechanisms generated by rows of trapezoidal vortex generators. The turbulent macrostructures of these streamwise vortices appear greatly to enhance radial convective transfer. Due to Kelvin-Helmholtz instability, the shear layer shed from the tab's edge becomes unstable and generates periodic transverse vortices that enhance fluid mixing and heat transfer. A global performance analysis of the high-efficiency vortex (HEV) heat exchanger designed to exploit these embedded vortices, shows that the HEV is very competitive with other multifunctional heat exchangers/reactors, especially due to its very low energy consumption. (C) 2010 Elsevier Ltd. All rights reserved.

Dynamic parameters of buildings in Beirut (Lebanon) were investigated based on ambient vibration method for the risk and vulnerability assessment. Indeed the country is threatened by a high seismic hazard due to its location near major faults, combined to a high seismic risk caused by urban, economic and political chaos in addition to the lack of implementing a seismic design code (introduced recently in 2005). Researchers do not miss any opportunity to trigger the alarm and increase studies in the seismic field to reduce this risk. For this study, 330 RC buildings were measured, dynamic parameters extracted and a statistical analysis performed to identify correlations with geometrical characteristics. The regressions show that only the building height or number of floors N is statistically relevant for the estimation of the fundamental period T and the correlation between them is linear: T = N/25 for rock sites and N/18 for soft sites. The significant difference leads to the conclusion that the natural period of a structure depends on the type of soil. Moreover measured frequencies are compared to those estimated in seismic building codes. The latter significantly overestimates the recorded periods by 80%, while the measured damping exhibits a striking correlation with the frequency; the taller the building the lower is the damping. However results obtained in other areas based on ambient vibration are coherent. Part of the large discrepancy with building code recommendations may be due to the very low level of excitation. However it is a significant variation to be consistent with the observed frequency shifts for severely damaged structures., Les paramètres dynamiques des bâtiments à Beyrouth (Liban) ont été mesurés en se basant sur la méthode des vibrations ambiantes pour l'évaluation du risque et de la vulnérabilité sismique. Le pays est menacé par un aléa sismique élevé en raison de son emplacement près de failles majeures, combiné à un risque sismique important dû au chaos urbain, économique et politique, en plus de l'absence de l'application d'un code parasismique (introduit récemment en 2005). Ainsi des travaux scientifiques plus poussés sont requis pour réduire ce risque. Pour cette étude, 330 bâtiments en béton armé ont été mesurés, les paramètres dynamiques extraits et une analyse statistique réalisée pour établir des corrélations avec les paramètres géométriques. Les régressions montrent que seule la hauteur du bâtiment ou le nombre d'étages N est statistique-ment pertinente pour l'estimation de la période fondamentale T, avec une corrélation linéaire: T = N/25 pour les sites rocheux et N/18 pour les sites mous. La différence significative conduit à la conclusion que la période fondamentale de la structure dépend du type de sol. Les fréquences mesurées sont également comparées à celles calculées dans le code parasis-mique. Ce dernier surestime considérablement les périodes enregistrées de 80%, tandis que l'amortissement mesuré montre une corrélation bien nette avec la fréquence; au plus grand bâtiment correspond le plus faible amortissement. Cependant, les résultats obtenus sont cohérents avec ceux obtenus dans d'autres régions. Une partie de l'écart important avec le code du bâtiment peut être dû au très faible niveau d'excitation. Mais cette différence est si large qu'elle n'est pas consistente avec les variations de fréquences observées pour de fortes excitations

International audience; The composite materials are nowadays widely used in aeronautical domain. These materials are subjected to different types of loading that can damage a part of the structure. This diminishes the resistance of the structure to failure. In this paper, matrix cracking and delamination propagation in composite laminates are simulated as a part of damage. Two different computational strategies are developed: (i) a cohesive model (CM) based on the classical continuum mechanics and (ii) a continuous damage material model (CDM) coupling failure modes and damage. Another mixed methodology (MM) is proposed using the continuous damage model for delamination initiation and the cohesive model for 3D crack propagation and mesh openings. A good agreement was obtained when compared simple characterization tests and corresponding simulations.

À paraître dans Archiv der Mathematik.; International audience; We prove lower bounds for the eigenvalues of the Spin c Dirac operator on submanifolds. These estimates are expressed in terms of extrinsic and intrinsic quanti-ties. We also give estimates involving the Energy-Momentum tensor as well as conformal bounds. The limiting cases of these estimates give rise to particular spinor fields, called generalized twisted Killing spinors, which are also studied.