Degradation and healing in a generalized neo-Hookean solid due to infusion of a fluid

The mechanical response and load bearing capacity of high performance polymer composites changes due to diffusion of a fluid, temperature, oxidation or the extent of the deformation. Hence, there is a need to study the response of bodies under such degradation mechanisms. In this paper, we study the effect of degradation and healing due to the diffusion of a fluid on the response of a solid which prior to the diffusion can be described by the generalized neo-Hookean model. We show that a generalized neo-Hookean solid - which behaves like an elastic body (i.e., it does not produce entropy) within a purely mechanical context - creeps and stress relaxes when infused with a fluid and behaves like a body whose material properties are time dependent. We specifically investigate the torsion of a generalized neo-Hookean circular cylindrical annulus infused with a fluid. The equations of equilibrium for a generalized neo-Hookean solid are solved together with the convection-diffusion equation for the fluid concentration. Different boundary conditions for the fluid concentration are also considered. We also solve the problem for the case when the diffusivity of the fluid depends on the deformation of the generalized neo-Hookean solid.Comment: 24 pages, 10 figures, submitted to Mechanics of Time-dependent Material

Feedback control algorithms for the dissipation of traffic waves with autonomous vehicles

International audienceThis article considers the problem of traffic control in which an autonomous vehicle is used to regulate human piloted traffic to dissipate stop and go traffic waves. We first investigate the controllability of well-known microscopic traffic flow models, namely i) the Bando model (also known as the optimal velocity model), ii) the follow-the-leader model, and iii) a combined optimal velocity follow the leader model. Based on the controllability results, we propose three control strategies for an autonomous vehicle to stabilize the other, human-piloted traffic. We subsequently simulate the control effects on the microscopic models of human drivers in numerical experiments to quantify the potential benefits of the controllers. Based on the simulations, finally we conduct a field experiment with 22 human drivers and a fully autonomous-capable vehicle, to assess the feasibility of autonomous vehicle based traffic control on real human piloted traffic. We show that both in simulation and in the field test that an autonomous vehicle is able to dampen waves generated by 22 cars, and that as a consequence, the total fuel consumption of all vehicles is reduced by up to 20%

Evaluation of photocatalytic activity of commercial red phosphorus towards the disinfection of E. coli and reduction of Cr (VI) under direct sunlight

Elemental photocatalysts are getting the attention of material scientists as a new class of visible light photocatalysts in recent years. Hence it is important to understand and evaluate their phtocatalytic activity for the rationale design and development of new catalysts at low cost. In this regard, we choose commercial red phosphorus as elemental photocatalyst and we evaluate its activity towards the disinfection of E. coli and reduction of Cr (VI) under natural sunlight. The measured bandgap of red phosphorus is 2.0 eV matches with theoretical value and indicates the suitability of the material as photocatalyst under direct sunlight. Moreover, red phosphorus also has optimum valence and conduction band levels for the successful photo-generation of reactive oxygen species (ROS). These photogenerated ROS could help to achieve the disinfection of E. coli in 50 min. In the case of photocatalytic reduction of Cr (VI), 98% of Cr (VI) reduction has been achieved is in 60 min at pH 2. The rate of Cr (VI) reduction decreases with an increase in pH value similar to the reports with other metal oxide photocatalysts