Modèle de planification tactique de chaîne d'approvisionnement soumise à des régulations environnementales

La problématique environnementale étant mise en avant lors des dernières décennies, la gestion de la chaîne d’approvisionnement devient de plus en plus complexe. Les grandes chaînes logistiques étant des acteurs majeurs du réchauffement climatique et des dommages causés à notre environnement, les entreprises concernées se retrouvent au centre de la polémique et de plus en plus elles doivent rendre des comptes au gouvernement ainsi qu’à leurs consommateurs. On utilise communément le terme de chaîne logistique durable lorsque les traditionnelles considérations économiques sont élargies aux dimensions environnementales et sociales, représentant ainsi un équilibre permettant à une activité industrielle de perdurer dans le temps sans causer de dommage à son entourage. C’est dans cette logique que s’inscrit ce travail de recherche, visant en particulier deux règlementations environnementales d’actualité pour les entreprises Québécoises : les limitations relatives aux émissions de gaz à effet de serre et le principe de compensation aux services de collecte. Dans ce travail nous avons mis en place un modèle d’optimisation linéaire permettant d’analyser les décisions tactiques d’approvisionnement en composants éco-conçus versus standards chez différents fournisseurs. Aussi la formulation mathématique utilisée permet d’évaluer le plan optimal de production aux usines manufacturières au moyen de deux technologies distinctes : standard versus propre. Le raisonnement appliqué suit trois étapes principales : tout d’abord une résolution préliminaire permet d’établir le plan optimal d’approvisionnement et de production dans le cas où l’entreprise étudiée n’est pas encore assujettie aux lois environnementales. Par la suite les simulations réalisées permettent de tester ce plan optimal lorsqu’il est soumis tout d’abord à une seule puis aux deux législations mentionnées plus haut simultanément. Si dans un premier temps nous privilégions les données réelles en vigueur actuellement dans la province du Québec, la suite de notre étude admet l’hypothèse que ces récentes règlementations vont être renforcées dans les prochaines années. Ainsi nous analysons les éventuelles conséquences d’un durcissement des législations sur le plan tactique optimal d’approvisionnement et de production de notre chaîne logistique

A Study of Nanoclay Reinforcement of Biocomposites Made by Liquid Composite Molding

Liquid composite molding (LCM) processes are widely used to manufacture composite parts for the automotive industry. An appropriate selection of the materials and proper optimization of the manufacturing parameters are keys to produce parts with improved mechanical properties. This paper reports on a study of biobased composites reinforced with nanoclay particles. A soy-based unsaturated polyester resin was used as synthetic matrix, and glass and flax fiber fabrics were used as reinforcement. This paper aims to improve mechanical and flammability properties of reinforced composites by introducing nanoclay particles in the unsaturated polyester resin. Four different mixing techniques were investigated to improve the dispersion of nanoclay particles in the bioresin in order to obtain intercalated or exfoliated structures. An experimental study was carried out to define the adequate parameter combinations between vacuum pressure, filling time, and resin viscosity. Two manufacturing methods were investigated and compared: RTM and SCRIMP. Mechanical properties, such as flexural modulus and ultimate strength, were evaluated and compared for conventional glass fiber composites (GFC) and flax fiber biocomposites (GFBiores-C). Finally, smoke density analysis was performed to demonstrate the effects and advantages of using an environment-friendly resin combined with nanoclay particles

Measurement of the in-plane thermal conductivity of long fiber composites by inverse analysis

ABSTRACT: In the present work, inverse thermal analysis of heat conduction is carried out to estimate the in-plane thermal conductivity of composites. Numerical simulations were performed to determine the optimal configuration of the heating system to ensure a unidirectional heat transfer in the composite sample. Composite plates made of unsaturated polyester resin and unidirectional glass fibers were fabricated by injection to validate the methodology. A heating and cooling cycle is applied at the bottom and top surfaces of the sample. The thermal conductivity can be deduced from transient temperature measurements given by thermocouples positioned at three chosen locations along the fibers direction. The inverse analysis algorithm is initiated by solving the direct problem defined by the one-dimensional transient heat conduction equation using a first estimate of thermal conductivity. The integral in time of the square distance between the measured and predicted values is the criterion minimized in the inverse analysis algorithm. Finally, the evolution of the in-plane composite thermal conductivity can be deduced from the experimental results by the rule of mixture

Progress in experimental and theoretical evaluation methods for textile permeability

ABSTRACT: A great amount of attention has been given to the evaluation of the permeability tensor and several methods have been implemented for this purpose: experimental methods, as well as numerical and analytical methods. Numerical simulation tools are being seriously developed to cover the evaluation of permeability. However, the results are still far from matching reality. On the other hand, many problems still intervene in the experimental measurement of permeability, since it depends on several parameters including personal performance, preparation of specimens, equipment accuracy, and measurement techniques. Errors encountered in these parameters may explain why inconsistent measurements are obtained which result in unreliable experimental evaluation of permeability. However, good progress was done in the second international Benchmark, wherein a method to measure the in-plane permeability was agreed on by 12 institutes and universities. Critical researchers’ work was done in the field of analytical methods, and thus different empirical and analytical models have emerged, but most of those models need to be improved. Some of which are based on Cozeny-Karman equation. Others depend on numerical simulation or experiment to predict the macroscopic permeability. Also, the modeling of permeability of unidirectional fiber beds have taken the greater load of concern, whereas that of fiber bundle permeability prediction remain limited. This paper presents a review on available methods for evaluating unidirectional fiber bundles and engineering fabric permeability. The progress of each method is shown in order to clear things up

A dimensionless characteristic number for process selection and mold design in composites manufacturing : part I — theory

ABSTRACT: The present article introduces a dimensionless number devised to assist composite engineers in the fabrication of continuous fiber composites by Liquid Composite Molding (LCM), i.e., by injecting a liquid polymer resin through a fibrous reinforcement contained in a closed mold. This dimensionless number is calculated by integrating the ratio of the injection pressure to the liquid viscosity over the cavity filling time. It is hereby called the “injectability number” and provides an evaluation of the difficulty to inject a liquid into a porous material for a given part geometry, permeability distribution, and position of the inlet gate. The theoretical aspects behind this new concept are analyzed in Part I of the article, which demonstrates the invariance of the injectability number with respect to process parameters like constant and varying injection pressure or flow rate. Part I also details how process engineers can use the injectability number to address challenges in composite fabrication, such as process selection, mold design, and parameter optimization. Thanks to the injectability number, the optimal position of the inlet gate can be assessed and injection parameters scaled to speed up mold design. Part II of the article completes the demonstration of the novel concept by applying it to a series of LCM process examples of increasing complexity

Impact of an interatrial shunt device on survival and heart failure hospitalization in patients with preserved ejection fraction

Aims: Impaired left ventricular diastolic function leading to elevated left atrial pressures, particularly during exertion, is a key driver of symptoms and outcomes in heart failure with preserved ejection fraction (HFpEF). Insertion of an interatrial shunt device (IASD) to reduce left atrial pressure in HFpEF has been shown to be associated with short‐term haemodynamic and symptomatic benefit. We aimed to investigate the potential effects of IASD placement on HFpEF survival and heart failure hospitalization (HFH). Methods and results: Heart failure with preserved ejection fraction patients participating in the Reduce Elevated Left Atrial Pressure in Patients with Heart Failure study (Corvia Medical) of an IASD were followed for a median duration of 739 days. The theoretical impact of IASD implantation on HFpEF mortality was investigated by comparing the observed survival of the study cohort with the survival predicted from baseline data using the Meta‐analysis Global Group in Chronic Heart Failure heart failure risk survival score. Baseline and post‐IASD implant parameters associated with HFH were also investigated. Based upon the individual baseline demographic and cardiovascular profile of the study cohort, the Meta‐analysis Global Group in Chronic Heart Failure score‐predicted mortality was 10.2/100 pt years. The observed mortality rate of the IASD‐treated cohort was 3.4/100 pt years, representing a 33% lower rate (P = 0.02). By Kaplan–Meier analysis, the observed survival in IASD patients was greater than predicted (P = 0.014). Baseline parameters were not predictive of future HFH events; however, poorer exercise tolerance and a higher workload‐corrected exercise pulmonary capillary wedge pressure at the 6 months post‐IASD study were associated with HFH. Conclusions: The current study suggests IASD implantation may be associated with a reduction in mortality in HFpEF. Large‐scale ongoing randomized studies are required to confirm the potential benefit of this therapy

One-year outcomes after transcatheter insertion of an interatrial shunt device for the management of heart failure with preserved ejection fraction

Background—Heart failure with preserved ejection fraction has a complex pathophysiology and remains a therapeutic challenge. Elevated left atrial pressure, particularly during exercise, is a key contributor to morbidity and mortality. Preliminary analyses have demonstrated that a novel interatrial septal shunt device that allows shunting to reduce the left atrial pressure provides clinical and hemodynamic benefit at 6 months. Given the chronicity of heart failure with preserved ejection fraction, evidence of longer-term benefit is required. Methods and Results—Patients (n=64) with left ventricular ejection fraction ≥40%, New York Heart Association class II–IV, elevated pulmonary capillary wedge pressure (≥15 mm Hg at rest or ≥25 mm Hg during supine bicycle exercise) participated in the open-label study of the interatrial septal shunt device. One year after interatrial septal shunt device implantation, there were sustained improvements in New York Heart Association class (P<0.001), quality of life (Minnesota Living with Heart Failure score, P<0.001), and 6-minute walk distance (P<0.01). Echocardiography showed a small, stable reduction in left ventricular end-diastolic volume index (P<0.001), with a concomitant small stable increase in the right ventricular end-diastolic volume index (P<0.001). Invasive hemodynamic studies performed in a subset of patients demonstrated a sustained reduction in the workload corrected exercise pulmonary capillary wedge pressure (P<0.01). Survival at 1 year was 95%, and there was no evidence of device-related complications. Conclusions—These results provide evidence of safety and sustained clinical benefit in heart failure with preserved ejection fraction patients 1 year after interatrial septal shunt device implantation. Randomized, blinded studies are underway to confirm these observations

Numerical prediction of saturation in dual scale fibrous reinforcements during Liquid Composite Molding

This paper presents a fractional flow model based on two-phase flow, resin and air, through a porous medium to simulate numerically Liquid Composites Molding (LCM) processes. It allows predicting the formation, transport and compression of voids in the modeling of LCM. The equations are derived by combining Darcy’s law and mass conservation for each phase (resin/air). In the model, the relative permeability and capillary pressure depend on saturation. The resin is incompressible and the air slightly compressible. Introducing some simplifications, the fractional flow model consists of a saturation equation coupled with a pressure/velocity equation including the effects of air solubility and compressibility. The introduction of air compressibility in the pressure equation allows for the numerical prediction of the experimental behavior at low constant resin injection flow rate. A good agreement was obtained between the numerical prediction of saturation in a glass fiber reinforcement and the experimental observations during the filling of a test mold by Resin Transfer Molding (RTM). 2015 Elsevier Ltd. All rights reserved.The authors acknowledge financial support of the Spanish Government (Project DPI2013-44903-R-AR).Gascón Martínez, ML.; García Manrique, JA.; Lebel, F.; Ruiz, E.; Trochu, F. (2015). Numerical prediction of saturation in dual scale fibrous reinforcements during Liquid Composite Molding. Composites Part A: Applied Science and Manufacturing. 77:275-284. https://doi.org/10.1016/j.compositesa.2015.05.019S2752847

A Comparative Study of Dispersion Techniques for Nanocomposite Made with Nanoclays and an Unsaturated Polyester Resin

Over the last few years, polymer/clay nanocomposites have been an area of intensive research due to their capacity to improve the properties of the polymer resin. These nanocharged polymers exhibit a complex rheological behavior due to their dispersed structure in the matrix. Thus, to gain fundamental understanding of nanocomposite dispersion, characterization of their internal structure and their rheological behavior is crucial. Such understanding is also key to determine the manufacturing conditions to produce these nanomaterials by liquid composite molding (LCM) process. This paper investigates the mix of nanoclays particles in an unsaturated polyester resin using three different dispersion techniques: manual mixing, sonication, and high shear mixing (HSM). This paper shows that the mixing method has a significant effect on the sample morphology. Rheology, scanning electron microscopy (SEM), and differential scanning calorimetry (DSC) characterization techniques were used to analyze the blends morphology and evaluate the nanoclays stacks/polymer matrix interaction. Several phenomena, such as shear thinning and premature polymer gelification, were notably observed

058 The ongoing MESAMI translational research program

PurposeDespite the improvement of pharmacological and surgical therapies, the mortality related to ischemic heart failure remains high. During the last years, bone marrow-mesenchymal stem cell (BM-MSC) therapy has been proposed as a novel approach for the prevention and therapy of heart failure. Intramyocardial injection allows concentration of grafted cells within the injured zone. However, a major problem of with intraparenchymal route of administration is the early death of most of grafted cells. The goal of the MESAMI program is to evaluate the effect of intramyocardial administration of BM-MSC preconditioned or not with the pineal hormone melatonin in ischemic cardiomyopathy.Methods and ResultsOur preclinical investigations have designed a preconditioning strategy of BM-MSCs with the melatonin that significantly increases survival and efficacy of grafted cells in animal models of myocardial ischemia. Melatonin treatment significantly ameliorates the beneficial effects of BM-MSC on the recovery of cardiac function. In the mean time, we started a phase I clinical trial in patients with severe ischemic cardiomyopathy and no option of revascularization, using the NOGA XP system to guide injections into the myocardium. Based on our basic research results, we are developing a multicenter phase II trial on the effects of intramyocardial administration of melatonin-preconditioned BM-MSC in patients with chronic ischemic cardiomyopathy.ConclusionThe ongoing MESAMI program is representative of a translational research program in France