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Supercritical CO2‐assisted extrusion foaming: A suitable process to produce very lightweight acrylic polymer micro foams
No full textInternational audienceA strategy of CO2-assisted extrusion foaming of PMMA-based materials was established to minimize both foam density and porosities dimension. First a highly CO2-philic block copolymer (MAM: PMMA-PBA-PMMA) was added in PMMA in order to improve CO2 saturation before foaming. Then the extruding conditions were optimized to maximize CO2 uptake and prevent coalescence. The extruding temperature reduction led to an increase of pressure in the barrel, favorable to cell size reduction. With the combination of material formulation and extruding strategy, very lightweight homogeneous foams with small porosities have been produced. Lightest PMMA micro foams (ρ = 0.06 g cm−3) are demonstrated with 7 wt% CO2 at 130°C and lightest blend micro foams (ρ = 0.04 g cm−3) are obtained at lower temperature (110°C, 7.7 wt% CO2). If MAM allows a reduction of Tfoaming, it also allows a much better cell homogeneity, an increase in cell density (e.g., from 3.6 107 cells cm−3 to 2 to 6 108 cells cm−3) and an overall decrease in cell size (from 100 to 40 μm). These acrylic foams produced through scCO2-assisted extrusion has a much lower density than those ever produced in batch (ρ ≥ 0.2 g cm−3)
Compiling capacitated single-item lot-sizing problem in a CostMDD
No full textEdited by Alain Bernard, Alexandre Dolgui, Hichem Haddou Benderbal, Dmitry Ivanov, David Lemoine, Fabio SgarbossaInternational audienceThis paper deals with capacitated single-item lot sizing problem (CLSP) in an interactive support system context. The interaction is done thanks to queries to the system: The decision-maker makes partial choices and asks about the consequences in terms of costs but also about possible inventory levels. Hence, three fundamental queries are investigated: Find production plans with a cost less than K; Find possible plans with conditioning on a pair of variables (production and inventory); Find the production plans that simultaneously satisfy the previous queries. A knowledge compilation approach is used and composed of two phases: offline and online. Offline, a top-down algorithm computes cost multivalued decision diagrams. While online, we show how cost multivalued decision diagrams can improve the reactivity of answers to queries. The proposed approach is compared to classical constraint programming with CP Optimizer. Tests indicate that our algorithm is more efficient than CP resolving in terms of computation time
Polymer Nanocomposites for Energy Applications
No full textInternational audienceIn Polymer Nanocomposites for Energy Applications, a team of distinguished researchers delivers a comprehensive review of the synthesis and characterization of polymer nanocomposites, as well as their applications in the field of energy. Succinct and insightful, the book explores the storage of electrical, magnetic, and thermal energy and hydrogen. It also discusses energy generation by polymer-based solar cells. Finally, the authors present a life cycle analysis of polymer nanocomposites for energy applications and provide four real-world case studies where these materials have been successfully used
A Two-Temperature Model Based on Fin-Approximation for Transient Longitudinal Heat Transfer in Unidirectional Composite
No full textInternational audienceThe reliability of a two-temperature model is assessed in the case of longitudinal heat transfer in unidirectional composites. One interest is that it makes it possible to apply separate boundary conditions or source terms on the fibre and the matrix (emissivity for example), without necessitating an explicit description of the fibre and matrix domains. For the sake of simplicity, the model under study is based on a fin-approximation in both fibre and matrix, which implies a high interfacial thermal resistance. The range of validity of this assumption is investigated by comparing the model to an axisymmetric one-temperature model, using non-dimension variables and Dirichlet boundary conditions. It turns out that this range of validity is strongly dependent on the parameters
The role of project managers experience in success of innovative complex project
No full textInternational audienceThe most appealing concept in the project management literature is ``success''. However,achieving this success in projects comes with many challenges. Particularly in innovative complexprojects managed with strategic alliances. Because in addition to the challenges and inherentuncertainties of the project, the risk of non-cooperation between the partners is inevitable. Moreover,work experience is a key noticeable productivity characteristic in project management. The purpose ofthis research is to take a deeper look into the success of complex projects, focusing on the role ofproject managers’ experience in their opinion on some of the factors influencing the success ofcomplex projects. A standard survey is designed and used to gather data from European projectmanagers involved in complex projects with more than one partner. Then, the gathered data is used toperform Spearman’s correlation coefficient analysis to investigate, first, the role of project managers'work experience on the project success, and second, the role of project managers' work experience ontheir perception of project success factors. Finally, we try to provide suggestions for less experiencedproject managers and decision-makers to increase the chance of success in strategic alliances
Long-wave instabilities of evaporating/condensing viscous film flowing down a wavy inclined wall: Interfacial phase change effect of uniform layers
No full textInternational audienceThe interfacial phase change effect on a thin film flowing down an undulated wall has been investigated in the present study. The study is performed for a general periodic undulated bottom of moderate steepness that is long compared to the film thickness, followed by a case study over the sinusoidal bottom. The long-wave instabilities of the ununiform film are used by deriving a nonlinear evolution equation in the classical long-wave expansion method framework. The one-equation model can track the free surface evolution and involve the bottom undulation, viscosity, gravity, surface tension, and phase change (evaporation/condensation) effects. Linear stability analysis shows that the bottom steepness ζ has a dual role. In the downhill region, increasing ζ destabilizes, whereas increasing ζ stabilizes in the uphill region. Weakly nonlinear waves are studied using the method of multiple scales to obtain the complex Ginzburg–Landau equation. The results show that both supercritical and subcritical solutions are possible for evaporating and condensate film. Interestingly, while one subcritical region is visible for an evaporating film, two subcritical unstable regions are found for condensate film. The numerical solution of the free-surface equation demonstrates the finite-amplitude behavior that tends to dry out for an evaporating film. For condensate film, the thickness increases rapidly. The rupture dynamics highly depend on the initial perturbation, and the bottom steepness has a negligible effect on it. Kutateladze number has a significant impact on the stability characteristic of the film flow as it represents a sort of efficiency of phase change that occurs at the interface
Vers un prototype de mise à jour des plannings long-terme dans le secteur du service à domicile
No full textInternational audienceThis book is centered around the development of agile, high-performing healthcare institutions that are well integrated into their environment. The aim is to take advantage of artificial intelligence, optimization and simulation methods to provide solutions to prevent, anticipate, monitor and follow public health developments in order to intervene at the right time, using tools and resources that are both appropriate and effective. The focus is on the people involved – the patients, as well as medical, technical and administrative staff – in an effort to provide an efficient healthcare and working environment that meets safety, quality and productivity requirements.Healthcare Systems has been written by healthcare professionals, researchers in science and technology as well as in the social sciences and humanities from various French-speaking countries. It explores the challenges and opportunities presented by digital technology in our practices, organizations and management techniques
Correlation between microstructure and cyclic behavior of 316L stainless steel obtained by Laser Powder Bed Fusion
No full textInternational audienceIn this work, stainless steel 316L obtained by Laser Powder Bed Fusion (L-PBF) has been produced and characterized. The experimental campaign focuses on the samples in the as-built state under cyclic tension-compression loadings. Low cycle fatigue (LCF) and high cycle fatigue (HCF) tests are carried out. Microstructure observations are performed before and after the loadings. As-built L-PBF 316L has a good LCF performance despite the presence of surface defects but a low fatigue limit in the HCF regime. Removing the surface roughness has a beneficial effect but does not improve the fatigue strength to that of machined wrought 316L. Observations on the microstructure of fatigue samples indicate that LCF is dominated by the local plastic deformation, which is mostly achieved by the slip in the studied material and is not sensitive to the defect. The lack-of-fusion defect impairs the fatigue resistance in the HCF regime
Moussage par CO2 supercritique de composites à matrice biopolymère chargée de fibres végétales
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A comparative study of chemical treatment by MgCl2, ZnSO4, ZnCl2, and KOH on physicochemical properties and acetaminophen adsorption performance of biobased porous materials from tree bark residues
No full textInternational audiencePreparing sustainable and highly efficient biomass-based carbon materials (BBPM) as adsorbents remains a challenge for organic pollutant management. In this work, novel biobased carbon material has been synthesized via facile, sustainable, and different single-step pyrolysis chemical methods (KOH, ZnCl2, ZnSO4, and MgCl2) using a Norway spruce bark as suitable and efficient carbon precursor. The effects of each chemical activator on the physicochemical structure of synthesized were thoroughly investigated as well as its performance on the acetaminophen adsorption. The results showed that the use of different chemical activation provoked remarkable differences in the BBPM physicochemical characteristics. The KOH activation generated material with the highest specific surface area (2209 m2 g−1), followed by ZnCl2 (1019 m2 g−1), ZnSO4 (446 m2 g−1), and MgCl2 (98 m2 g−1). The chemical characterization of the carbon materials indicated that the activation of MgCl2 yielded a material around three times more hydrophobic when compared with the other activation methods. The acetaminophen removal showed to be ultrafast, not only due to the BBPM’s microstructure but also to the abundant active sites provided by the different chemical activation methods. The adsorption equilibrium times were reached at 1 min for BBPM-KOH and BBPM-MgCl2 and 15 min for BBPM-ZnSO4 and BBPM-ZnCl2. The adsorption process suggests that the pore-filling mechanism mainly dominates the acetaminophen removal but also some physical-chemical interactions such as hydrogen bonding between the amide group of acetaminophen and oxygenated or nitrogenated groups of biochar, π-π interactions between the aromatic ring of the pharmaceutical and the aromatics of biochar, n-π interaction, van der Waals interactions. The BBPM regeneration studies showed very good cyclability; in the 3rd cycle, the removal was approximately 70% for all four samples. The samples were also used to treat two synthetic effluents, which attained a removal percentage up to 91.9%