Conception et réalisation de rover en matériaux composite M Rover 12

La majorité des robots, en particulier ceux utilisés dans l’industrie, sont immobiles. Ces dernières années beaucoup d'attention a été concentrée sur le succès des robots mobiles. Aujourd'hui, le marché commercial de la robotique mobile est toujours relativement restreint. Les applications de ses robots peuvent se trouver dans de nombreuses activités 'épuisantes, salissantes ou dangereuses', mais également pour des applications ludiques ou de service, comme l'assistance aux personnes âgées ou handicapées. L’application visée est la validation d’une conception et sa fabrication en utilisant des matériaux composites comme base du robot mobile. Nous décrivons de manière formelle la structure complète du robot mobile. Cette synthèse aborde l’interaction entre le robot mobile et un partenaire humain distant ou partageant son environnement dans le cadre de la robotique d’assistance à la personne. Une telle interaction s'exprime pleinement dans des situations où l'homme et le robot doivent agir en collaboration pour réaliser une tâche où ils partagent l'espace de travail et se perçoivent directement. Le succès d’un robot mobile dépend principalement de la bonne adéquation de la plate forme mobile à la stratégie globale que nous avons déterminé. Dans ce travail, quatre aspects fondamentaux de l’étude, conception, fabrication et validation de la base mobile en matériaux composite (polyptère, tissu) du prototype du robot mobile seront abordés. En effet, que ce soit pour un seul individu ou pour toute une équipe, se lancer dans la conception et la réalisation d'un robot est toujours un défi

Modélisation numérique d'un pipe en composite stratifié fissuré sous compression axiale

Les coques minces sont utilisées largement dans de nombreux domaines suite à leur excellente capacité portante. Par conséquent, la faible épaisseur de ces structures les rend sensibles au phénomène de flambage. Le but de cette étude est focalisé sur l’effet de la présence de défauts géométriques sur la résistance des coques cylindriques minces (pipes en composite stratifié) soumises à la compression axiale en présence de fissures longitudinales, radiales et inclinées par rapport à l'horizontal. L'approche adoptée est basée sur les équations du mouvement, qui sont numériquement résolues au moyen du code des éléments finis (ABAQUS/Explicit). Les résultats indiquent que l'augmentation du rayon du pipe conduit à la diminution du paramètre de flambage et les valeurs maximales sont obtenues pour les plus faibles orientations des fibres. Par ailleurs, les contraintes maximales sont obtenues pour le rayon de 400mm. Par ailleurs, l'augmentation du nombre de plis du pipe en composite mène à l'accroissement du paramètre du flambage. La taille de la fissure, son orientation et sa position dans le pipe sont mis en évidence

Effects of a high-dose 24-h infusion of tranexamic acid on death and thromboembolic events in patients with acute gastrointestinal bleeding (HALT-IT): an international randomised, double-blind, placebo-controlled trial

Background: Tranexamic acid reduces surgical bleeding and reduces death due to bleeding in patients with trauma. Meta-analyses of small trials show that tranexamic acid might decrease deaths from gastrointestinal bleeding. We aimed to assess the effects of tranexamic acid in patients with gastrointestinal bleeding. Methods: We did an international, multicentre, randomised, placebo-controlled trial in 164 hospitals in 15 countries. Patients were enrolled if the responsible clinician was uncertain whether to use tranexamic acid, were aged above the minimum age considered an adult in their country (either aged 16 years and older or aged 18 years and older), and had significant (defined as at risk of bleeding to death) upper or lower gastrointestinal bleeding. Patients were randomly assigned by selection of a numbered treatment pack from a box containing eight packs that were identical apart from the pack number. Patients received either a loading dose of 1 g tranexamic acid, which was added to 100 mL infusion bag of 0·9% sodium chloride and infused by slow intravenous injection over 10 min, followed by a maintenance dose of 3 g tranexamic acid added to 1 L of any isotonic intravenous solution and infused at 125 mg/h for 24 h, or placebo (sodium chloride 0·9%). Patients, caregivers, and those assessing outcomes were masked to allocation. The primary outcome was death due to bleeding within 5 days of randomisation; analysis excluded patients who received neither dose of the allocated treatment and those for whom outcome data on death were unavailable. This trial was registered with Current Controlled Trials, ISRCTN11225767, and ClinicalTrials.gov, NCT01658124. Findings: Between July 4, 2013, and June 21, 2019, we randomly allocated 12 009 patients to receive tranexamic acid (5994, 49·9%) or matching placebo (6015, 50·1%), of whom 11 952 (99·5%) received the first dose of the allocated treatment. Death due to bleeding within 5 days of randomisation occurred in 222 (4%) of 5956 patients in the tranexamic acid group and in 226 (4%) of 5981 patients in the placebo group (risk ratio [RR] 0·99, 95% CI 0·82–1·18). Arterial thromboembolic events (myocardial infarction or stroke) were similar in the tranexamic acid group and placebo group (42 [0·7%] of 5952 vs 46 [0·8%] of 5977; 0·92; 0·60 to 1·39). Venous thromboembolic events (deep vein thrombosis or pulmonary embolism) were higher in tranexamic acid group than in the placebo group (48 [0·8%] of 5952 vs 26 [0·4%] of 5977; RR 1·85; 95% CI 1·15 to 2·98). Interpretation: We found that tranexamic acid did not reduce death from gastrointestinal bleeding. On the basis of our results, tranexamic acid should not be used for the treatment of gastrointestinal bleeding outside the context of a randomised trial

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

The influence of bearing material on the wear produced, application on the prodisc-C cervical prothesis

Cervical disc prostheses are designed to replace the degenerated intervertebral disc and recover movement between the vertebrae. These prostheses are made of at least two elements with a ball and socket design; this allows movement between the elements. The articular surfaces wear out, the polyethylene cores deteriorate (failure of polyethylene), and produce wear debris. This study focused on the Prodisc-C cervical disc prosthesis model with the design ball and socket and three degrees of freedom (3 DOF). The aim is to clarify the difference between the two bearings materials, Metal-on-Polyethylene (MoP) and Metal-on-Poly-ether-ether-ketone (MoPEEK), in terms of contact and wear. We designed this prosthesis model in 3D using Solidworks design software. Then, we imported this model to the Ansys Workbench simulation software to do the numerical analysis. We have fixed the lower plate and a fixed compressive load of 150 N was first applied on the upper plate, Next, this compressive load was combined with a rotational displacement of 7.5° in flexion, 6° in lateral bending, and 4° in axial rotation on the upper plate. After the simulation, we found that the contact pressure for the bearing material MoP is 5.53 MPa and justified this value using the Hertzian theory P0 = 4.9 MPa. Then the contact pressure for the bearing material MoPEEK is 11.09 MPa, justified by the Hertzian theory P0 = 10.74 MPa. The clinical reference polyethylene-on-cobalt alloy (prosthesis with polyethylene core MoP) was 1.05mm3/million cycles, compared to 0.83 mm3/million cycles MoPEEK, a 20.95% discount has been won

3D Printing to support the shortage in personal protective equipment caused by COVID-19 pandemic

Currently, the emergence of a novel human coronavirus disease, named COVID-19, has become a great global public health concern causing severe respiratory tract infections in humans. Yet, there is no specific vaccine or treatment for this COVID-19 where anti-disease measures rely on preventing or slowing the transmission of infection from one person to another. In particularly, there is a growing eort to prevent or reduce transmission to frontline healthcare professionals. However, it is becoming an increasingly international concern respecting the shortage in the supply chain of critical single-use personal protective equipment (PPE). To that scope, we aim in the present work to provide a comprehensive overview of the latest 3D printing eorts against COVID-19, including professional additive manufacturing (AM) providers, makers and designers in the 3D printing community. Through this review paper, the response to several questions and inquiries regarding the following issues are addressed: technical factors connected with AM processes; recommendations for testing and characterizing medical devices that additively manufactured; AM materials that can be used for medical devices; biological concerns of final 3D printed medical parts, comprising biocompatibility, cleaning and sterility; and limitations of AM technology

Additive manufacturing in fighting against novel coronavirus COVID-19

Nowadays, COVID-19 also known as novel coronavirus has become a global pandemic by causing severe respiratory tract infections in humans without any definite treatment or vaccine. Therefore, disease control measures include slowing down or averting the transfer of this viral infection from person to person. Continuous efforts are carried out to avoid the transmission of this disease to frontline healthcare personnel using single-use personal protective equipment (PPE). However, a critical shortage in this equipment around the world is becoming an alarming concern. Therefore, it is vital to present a possible alternative to overcome the acute shortage of protective gear such as face masks against this infectious disease which can have universal accessibility and is easily available. Additive manufacturing (AM), also known as 3D printing, is a possible solution to overcome the shortage of protective gear and can play a vital role in supporting their conventional production supplies during this global pandemic situation. In this context, this paper provides a brief background study of COVID-19, its conventional preventive measure, and a detailed overview regarding the latest AM efforts including designers’ providers and makers in the 3D printing community. Moreover, numerous inquiries and questions such as technical factors, testing recommendations and characterization methods and biological concerns such as biocompatibility and sterilization for the AM manufactured medical devices are addressed in this paper. In the end, two examples of AM medical devices, i.e., face mask and Ambu bag ventilator, are presented and studied through numerical simulations

COVID-19: Current challenges regarding medical healthcare supplies and their implications on the global additive manufacturing industry

International audienceThe covid-19 outbreak has caused a shortage of masks and other healthcare products for the general public around the globe. In addition, it has also affected the supply of personal protective equipment (PPE) used by healthcare services because of a sudden increase in their demand. This significant disruption in the global supply chain of these products resulted in, leaving many staff and patients without protection. The additive manufacturing (AM) industry is going through extraordinary times and can provide emergency responses to help deal with the global crisis caused by the COVID-19 pandemic. The objective of the present work is therefore to perform an up-to-date review to determine the capacity of AM to provide exclusive benefits for the medical healthcare supplies sector to fight this current situation. In this review, it is found that AM technology has proved that it can be used as a volume manufacturing technology for the ongoing crisis. However, the standardization and certification are appeared to represent the main challenges for adopting the AM in healthcare against COVID-19. Furthermore, additively manufactured materials for medical applications must be developed for medical environments. Most printed medical products for COVID-19 require biocompatibility evaluation and shall prove their ability to sterilize. Finally, this review concluded that AM technology can fulfill the requirements of face masks and ventilator parts for healthcare systems for proper controlling and treating of COVID-19 patients when the safety and efficacy of these devices are ensured

Effect of carbon nanotubes on the in-plane dynamic behavior of a carbon/epoxy composite under high strain rate compression using SHPB

International audienceFiber reinforced composites have wide structural applications and vast research has been going on to improve their mechanical performance when subjected to quasi-static loading but, study of their dynamic behavior is still underdeveloped. For this reason, scientists have been continuously working on developing methods to improve their dynamic characteristics and addition of nanofillers suchs as Carbon Nanotubes (CNTs) as reinforcement is considered a possible solution for developing future generation high-quality fiber reinforced nanocomposites. In this study, composite specimens are manufactured using Epon 862 Epoxy resin and T300 6 k carbon fibers, and each specimen contained different weight percentages of multi-walled Carbon nanotubes (MWCNTs) i.e. 0% as a reference, 0.5%, and 2%. Specimens were tested experimentally using the Split Hopkinson pressure bar device (SHPB) under different pressures to examine their dynamic response and damage behavior at high strain rates. During the dynamic compression tests, a high-speed camera was used to monitor and record the damage kinetics. The experimental characterization showed that the integration of CNTs in matrix has greatly influenced the dynamic response and damage mechanism of the Carbon Fiber Reinforced Polymers composite (CFRP). Mechanical behavior of specimens with each percentage demonstrated the enhancement of the mechanical properties and showed the increase of the dynamic characteristics and fracture resistance because of the increase in stiffness of matrix material and interfacial bonding between matix and fiber reinforcement

Graphene nanofillers as a player to improve the dynamic compressive response and failure behavior of carbon/epoxy composite

International audienceVast research has been going on to improve the mechanical performance of Carbon Fiber Reinforced Polymers composite (CFRP) when subjected to quasi-static loading but, investigation and modification of their dynamic behavior is still underdeveloped. This paper presents an experimental investigation on the effect of random dispersed graphene nanoplatelets (GNPs) on mechanical properties of CFRP composites under dynamic loading. Four different mass fractions of GNPs, 0%, 0.5%, 1%, and 2%, were considered in the experiments. Specimens were tested experimentally using the Split Hopkinson pressure bar device (SHPB) to examine their dynamic response and damage behavior at high strain rates. During the dynamic compression tests, a high-speed camera was used to monitor and record the damage kinetics. The experimental characterization showed that the integration of GNPs has greatly influenced the dynamic response and damage mechanism of the CFRP. Composite doped with 1% GNPs demonstrates the optimum enhancement of the mechanical properties of the composite specimens and shows an increase of the dynamic characteristics and fracture resistance