Portail des publications scientifiques IMT Mines Alès
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Comprehensive characterization of European house dust contaminants: Concentrations and profiles, geographical variability, and implications for chemical regulation and health risk
No full textInternational audienceThis study investigated the concentration profiles and geographical variability of contaminants in house dust across Europe. A collaborative trial (CT) was organized by the NORMAN network using pooled dust and advanced chromatographic and mass spectrometric techniques combined with suspect screening and non-target screening (NTS). Over 1200 anthropogenic compounds were tentatively identified. Additionally, seventy-five individual samples were subjected to target analysis and NTS. The median concentrations of most contaminants varied <3-fold across Europe, and the contaminant profile of European dust was similar to that of North American dust, which was investigated in a previous CT. This similarity may be attributed to the use of similar consumer articles and building materials throughout the developed world. Multivariate data analysis revealed geographical trends in contaminant distribution, with north-south gradients across Europe. Geographical trends were more frequently found for compounds with rapid release (pharmaceuticals, personal care products, fragrances, pesticides, biocides) and smoke-related compounds. The concentrations of chlorinated paraffins, polycyclic aromatic hydrocarbons (PAHs), perfluorinated alkyl substances and stimulants generally increased from north to south, whereas the biocides levels decreased from north to south. Despite widespread presence of in-use contaminants in dusts, some of the highest risks come from compounds that have been restricted for decades or more. These include di(2-ethylhexyl) phthalate (DEHP), polychlorinated biphenyl (PCB) 118 and polybrominated diphenyl ethers 47, 99, and 153. DEHP remains the most abundant contaminant in European house dust, while the other compounds are classified as persistent organic pollutants (POPs). Moreover, there is a striking lack of reliable toxicity data, particularly for emerging compounds. For instance, although acceptable daily intakes (ADIs) were examined for 202 compounds, only 46 had consensus-based ADI values. The results highlight the need for proactive measures to prevent hazardous chemicals from entering the market and for careful selection of substitute chemicals, when such are needed, to avoid regrettable substitutions
Effect of Supplementary Cementitious Materials (SCMs) on the Structural Build-Up of Cement Pastes
No full textInternational audienceThe comprehension of the effect of supplementary cementitious materials (SCMs) on the structural build-up is of great interest, especially for the development of modern concretes. The structural build-up of fresh cement paste describes the evolution of rheological properties with resting time and can be related to the loss of workability. It originates from particle flocculation and chemical changes and is mainly affected by the inter-particle distance and the nucleation of hydrates. The effect of SCMs on this structural build-up is complex and depends on several factors. This study aims to examine the effect of SCMs (fly ash, slag, limestone filler, and metakaolin) on the reversibility of the structural build-up of cement paste. It appears that the addition of slag, fly ash, or metakaolin leads to a decrease in the structural build-up with a negligible irreversible part, while cement paste with limestone filler (LF) exhibits the same trend as Portland cement paste. In addition, it appears that the reversibility of the structural build-up would not depend solely on chemical change
Towards a model-based simulation approach for safety analysis of complex systems
No full textInternational audienceCritical infrastructure systems are complex systems that need different stakeholders to work together, with specific engineering objectives and viewpoints. This paper proposes a literature review of safety analysis through simulation, integrating MBSE (Model-Based Systems Engineering), MBSA (Model-Based Safety Assessment), and M&S (Modelling & Simulation). As a result of the literature review, the cross of MBSE/MBSA/M&S does not appear to be well established. By transforming system models into safety models and using them as simulation foundations, our method intent to enable interoperability across the different model views and viewpoints. In addition, we conclude the paper with a tentative unified framework that may provide an innovative pathway for comprehensive safety analysis, advancing simulation-based verification and validation at conceptual engineering phases of complex systems
Surrogate Modelling with Deep Learning for Optimizing Manufacturing Assembly Lines
No full textInternational audienceAirbus Helicopters needs to modify its manufacturing lines and workshops to meet diverse client requests and growing demands for customization. The challenge is to develop adaptive, dynamic production systems and to optimize key performance indicators. The main goal is to maximize customer satisfaction and mini-mize delivery times, investments, costs, and work in progress. Airbus Helicopters has long used a classical simulation-based technique to define the best settings for its production lines. Nonetheless, the model needs 48 hours to complete each run and test a single set of parameters for the workshop. This paper presents an artificial intelligence based surrogate model designed to outperform traditional simulations by potentially delivering similar results much faster, in seconds rather than hours. It has been trained with synthetic data generated by a genetic algorithm and the simulation
Supplier Selection Considering Flexibility, Order Splitting, and Uncertainty of lead times
No full textInternational audienceEffective replenishment planning and inventory control are essential for the smooth operation and adaptability of supply chains. These aspects play a pivotal role in upholding a company’s competitiveness and triumph in today’s fiercely competitive markets. Supply chain planners encounter significant hurdles in choosing the most appropriate suppliers in diverse scenarios, reducing average inventory levels, and determining optimal safety lead times. This research tackles these challenges by examining and evaluating a multi-period replenishment planning issue within the framework of dynamic demand and multiple suppliers. The suppliers are pre-selected and defined by procurement costs, with lead times considered as independent discrete random variables with known and limited probability distributions. The goal is to optimize the distribution of order quantities among these pre-selected suppliers while minimizing the anticipated total cost. Two strategies and corresponding linear models are suggested to investigate the impact of dividing orders between suppliers, order crossover, and order flexibility. Numerical experiments provide evidence that concurrently considering splitting and flexibility yields benefits in terms of cost optimization
Small-scale BLEVE: Near-field aerial shock overpressure and impulse
No full textInternational audienceThis paper presents an investigation into one of the most damaging hazards associated with Boiling Liquid Expanding Vapor Explosion (BLEVE), specifically focusing on the near-field overpressure and impulse effects. Experiments were conducted at a small-scale to study the overpressure and impulse using aluminum tubes with a diameter of 50 mm and a length of 300 mm. The tubes were filled with pure propane liquid and vapor. The controlled variables, in this work included the failure pressure, the liquid fill level, and the weakened length along the tube top. These variables control the strength of the overpressure characterized by the peak overpressure amplitude, duration of this overpressure event, and the resultant impulse. Notably, these experiments at a small scale included experiments with a 100 % liquid fill level. This further confirmed that the vapor space is the main driver of the lead overpressure hazard. High-speed cameras and blast gauges effectively illustrated the progressive formation of the shock wave in both temporal and spatial dimensions. Furthermore, various predictive models available in the literature are discussed in this paper and new correlations were developed to quantify the overpressure duration and impulse. The current analysis aims to predict the potential consequences of overpressure events during a BLEVE
Stokes-darcy fluid flow simulations within 3d Interlock fabrics with capillary effects
No full textDOI Proceedings : 10.60691/yj56-np80International audienceResin Transfer Moulding is a widely used process in composite material manufacturing, involving the compaction of a fibrous 3D interlock preform to reach the desired Fibre Volume Fraction (FVF), followed by impregnation with liquid polymer resin. Understanding the dual-scale flows of resin within and between homogeneous equivalent porous yarns is essential for predicting impregnation defects. At the mesoscopic scale, fabric unit cells are characterised by yarn morphology and intra-yarn FVF fields, converted into a permeability tensor field via Darcy’s law. This dual-scale nature significantly affects saturated and unsaturated fluid flows, especially due to capillary phenomena within yarns, modelled by a capillary pressure. The aim is to develop a robust numerical framework for simulating fibrous media impregnation at the mesoscopic scale. Fluid flow is modelled by Darcy'sequation within porous yarns and by Stokes' equation between yarns, employing a monolithic approach with a mixed velocity-pressure formulation stabilised by a VMS method. Accurate description of resin flow within porous yarns requires locally oriented intra-yarn permeability tensor fields and capillary stress tensor at the resin-air interface. Additionally, pressure enrichment is introduced at the fluid front, represented by a level set function, to capture pressure discontinuity in Darcy domains. Saturated and unsaturated Stokes-Darcy fluid flow simulations are conducted to determine fabric permeability as a function of global FVF at different compactions and to evaluate the influence of capillary phenomena on the impregnation scenario
Fostering Mobile Field Hospitals Collaboration During Disaster Response for Seamless Continuity of Care: A Mini Review
No full textInternational audienceWhen mobile field hospitals are deployed in response to a disaster, they may sometimes face unprecedented challenges that require collaboration either with other mobile field hospitals or with existing regional hospitals to maintain continuity of care for the impacted populations. This article explores the pivotal role of enhancing healthcare team collaboration to ensure seamless care continuity during disaster response in an austere disaster-stricken environment. To improve patient outcomes during disasters, this study aims to investigate the barriers to care continuity in disaster response and highlight frameworks that can enhance healthcare team collaboration during sudden onset of disasters. Several bibliographical databases, including Pub Med, Science Direct, Web of Science, and Google Scholar were utilized. Articles examined from the databases were focused on state-of-the-art healthcare collaboration frameworks. To shed light on the difficulties and the necessity of implementing a collaborative healthcare disaster response framework, a case study of an American mobile field hospital deployed during the 2010 Haiti earthquake was examined. The literature review highlighted several factors that are responsible for lack of coordination during disaster response especially in an austere setting like Haiti. The review further highlights some frameworks that have the potential to improve care continuity in such an environment. In the event of a disaster, especially in austere settings like Haiti where the usual coordination mechanisms with regional or local government is difficult, deployed mobile hospitals must find alternative frameworks to enable them to work in tandem among themselves and with the local hospitals to improve the affected population’s continuity of care. The five frameworks highlighted have the potential to facilitate care coordination and hence continuity of care in such settings
A new strategy toward synthesis of novel bifunctional N- and S-bearing sorbent for platinum(IV) removal from aqueous solutions and acidic leaching residue of Pt/Al2O3 catalyst
No full textInternational audienceStrong incentive politics have been elaborated for promoting the recovery of precious metals from secondary resources. Solid leaching generates acidic effluents that can be pre-treated using precipitation steps for partial separation before applying sorption for metal recovery from mild acidic solutions. For this purpose, a new sorbent was designed carrying numerous N- and S-bearing reactive groups with good affinity for platinum (as chloroanionic species). Thiazole precursors were first reacted before being grafted (by free radical reaction) with triallyl cyanurate (to form CTTR sorbent). The material was characterized by a series of analytical tools (SEM, BET, FTIR, XPS, TGA, elemental analysis, and titration). The effect of pH combined with FTIR and XPS spectroscopy analyses allowed identifying the mechanisms involved in metal binding: electrostatic attraction of chloroplatinate anions with protonated amine groups (especially in acidic conditions), while at moderate acidic pH, metal sorption proceeds through ligand exchange and chelation onto N-based and S-based groups. Optimum sorption was found at pH close to 4 (near pHpzc value). Under selected experimental conditions, the equilibrium was reached in 25–35 min. The pseudo-first order rate equation fitted well experimental profile (though the resistance to intraparticle diffusion contributed to the kinetic control). The maximum sorption capacity at room temperature reached up to 1.58 mmol Pt g−1 (at pH 4). The sorption isotherm was successfully fitted by the Temkin equation. The sorption is spontaneous and exothermic (with reduction in maximum sorption capacity reaching up to 25 %, when temperature increases to 50 °C). Optimum platinum desorption was obtained with 0.3 M HCl solution (with solid/liquid ratio 1.67 g L−1) for complete desorption and enrichment factor close to 4.6. Complete desorption was maintained over 5 cycles, while the sorption efficiency decreased by less than 3.5 % at the fifth cycle. The sorbent showed remarkable stability for PGMs (Pd(II) in addition to Pt(IV)) against alkali-earth elements or base metals (from equimolar synthetic solutions); the selectivity is driven by the preference of the reactive groups (soft base and intermediary base) for soft PGM metals against hard and borderline metal ions; this selectivity is also affected by metal speciation (formation of chloro-anionic species). The valorization of platinum from non-compliant Pt/Al2O3 catalyst was investigated after leaching with aqua regia. Platinum was precipitated from the leachate with ammonium chloride. In a second step, aluminum was removed by precipitation at pH 5. The residual solution was then treated by adsorption on CTTR: optimum separation between Pt and Al was achieved at pH ≈ 3
Investigation of cathodic protection of reinforced concrete in marine environment for the application of floating offshore wind turbine
No full textInternational audienceReinforced concrete (RC) floaters to support floating offshore wind turbine (FOWT) can exhibit prematurecorrosion due to high chloride content in the marine environment. To address the concerns about theirdeterioration in harsh marine environment, such as corrosion of reinforcements, eventually influenced bybiofouling on the material’s surface, this study has been designed to understand the interrelations betweennatural seawater, biofouling, and cathodic protection for RC structures. The objective of the research studyis to quantify the effectiveness of cathodic protection using sacrificial aluminium galvanic anode inconjugation with biofilm development. However, this paper presents a part of the long-term research studyinvestigating the comparative effects of galvanic anodes on passive steel in concrete, using CEM I andCEM V cement types, in seawater. Experimental tests were conducted on RC blocks installed in the tidalzone of Banyuls-sur-mer harbour and connected to a data logger for continuous monitoring of theelectrochemical state of steel. After three months of immersion, the exposed surface of RC blocks exhibitedbiofouling, while its influence on the cathodic protection should be probed in detail. Monitoring the mixedpotential under temporal variations require careful consideration of tidal influences to ensure continuedprotection of reinforced concrete. Each binder was tested with three replicate RC blocks, in which therebars exhibited similar trends in mixed potential and protection current density over time. The aluminiumanode delivered slightly higher currents, resulting in greater consumption in the rebars of CEM I reinforcedconcrete blocks compared to those in CEM V