Pushing the limits of CAN - scheduling frames with offsets provides a major performance boost

International audienceWith the increasing amount of electronics, making best usage of the bandwidth becomes of primary importance in automotive networks. One solution that is being investigated by car manufacturers is to schedule the messages with offsets, which leads to a desynchronization of the message streams. As it will be shown, this “traffic shaping” strategy is very beneficial in terms of worst-case response times. In this chapter, the problem of choosing the best offsets is addressed in the case of Controller Area Network, which is a de-facto standard in the automotive world. Comprehensive experiments shown in this chapter give insight into the fundamental reasons why offsets are efficient, and demonstrate that offsets actually provide a major performance boost in terms of response times. These experimental results suggest that sound off-set strategies may extend the lifespan of CAN further, and may defer the introduction of FlexRay and additional CAN networks

Fine-Tuning MAC-Level Protocols for Optimized Real-Time Quality-of-Service

In distributed real-time systems, meeting the real-time constraints is mandatory but the satisfaction of other application-dependent criteria is most generally required as well. In particular, Networked Control Systems (NCS) are known to be sensitive to communication delays such as frame response time jitters. Well known Medium Access Control (MAC) algorithms such Non-Preemptive Deadline Monotonic (NP-DM) or Non-Preemptive Earliest Deadline First (NP-EDF) are efficient in terms of bandwidth usage but they may perform poorly regarding other application dependent performance criteria. This paper highlights a class of on-line scheduling policies targeted at scheduling frames at the MAC level, and provides a schedulability analysis that is valid for all policies within the considered class. As it will be shown, these algorithms are easily implementable on COTS components (e.g., Controller Area Network controllers) and offer good trade-offs between feasibility and the satisfaction of other application-dependent criteria such as the response time jitter

A non-rigid registration approach for quantifying myocardial contraction in tagged MRI using generalized information measures.

International audienceWe address the problem of quantitatively assessing myocardial function from tagged MRI sequences. We develop a two-step method comprising (i) a motion estimation step using a novel variational non-rigid registration technique based on generalized information measures, and (ii) a measurement step, yielding local and segmental deformation parameters over the whole myocardium. Experiments on healthy and pathological data demonstrate that this method delivers, within a reasonable computation time and in a fully unsupervised way, reliable measurements for normal subjects and quantitative pathology-specific information. Beyond cardiac MRI, this work redefines the foundations of variational non-rigid registration for information-theoretic similarity criteria with potential interest in multimodal medical imaging

Scheduling Configuration on Posix 1003.1b Systems

Posix 1003.1b compliant systems provide two well-specified scheduling policies, namely {\it sched\_rr} (Round-Robin like) and {\it sched\_fifo} (FPP like). Up to now, little has been done to take advantage of the combination of both policies to maximize schedulability. In this study, we propose two priority, policy and quantum assignment algorithms for Posix 1003.1b systems that are optimal with regards to the power of the feasibility test (i.e. its ability to distinguish feasible and non feasible configurations). Though much less complex than an exhaustive exploration, the exponential complexity of the algorithms limits their applicability to small or medium-size problems. This is why a heuristic is proposed to handle larger task sets. As shown in the experiments, our proposal allows achieving a significant gain in feasibility over FPP, and therefore using the computational resources at their fullest potential. In many cases where FPP does not lead to a feasible schedule, using both FPP and RR may provide an alternative to EDF, which, most often, is not implemented at the OS kernel level.

Improvements in the configuration of Posix 1003.1b scheduling

http://rtns07.irisa.frInternational audiencePosix 1003.1b compliant systems provide two well-specified scheduling policies, namely sched_rr (Round-Robin like) and sched_fifo (FPP like). Recently, an optimal priority and policy assignment algorithm for Posix 1003.1b has been proposed in the case where the quantum value is a system-wide constant. In this study, we extend this analysis to the case where quanta can be chosen on a task-per-task basis. The algorithm is shown to be optimal with regards to the power of the feasibility test (i.e. its ability to distinguish feasible and non feasible configurations). Though much less complex than an exhaustive exploration of the search space, the exponential complexity of the algorithm limits its applicability to small or medium-size problems. In this context, as it is shown in the experiments, our proposal allows achieving a significant gain in terms of feasibility over FPP and Posix with system-wide quanta, and therefore using the computational resources at their fullest potential

An improved SPH method for multi-phase simulations

In this work a new SPH model for simulating interface flows is presented. This new model is an extension of the formulation discussed in Colagrossi and Landrini (2003), and shows strong similarities with one proposed by Hu and Adams (2006) to study multiphase flow. The main difference between these two models is that the present formulation allows for simulating multiphase flows together with the presence of a free surface. The new formulation is validated on test cases for which reference solutions are available in literature. A Rayleigh-Taylor instability is first studied. Then, the rise of an air bubble in a water column is investigated. Finally, the model capabilities are illustrated on the case of a drop of a heavy fluid entering a tank filled with water

New On-Line Preemptive Scheduling Policies for Improving Real-Time Behavior

In real-time systems, schedulability is mandatory but other application-dependent performance criteria are most generally of interest. We first define the properties that a "good" real-time scheduling algorithm must possess. Then, we exhibit a class of easily-implementable policies that should be well suited to various applicative contexts because, in our experiments, these policies provide good trade-off between feasibility and the satisfaction of the application-dependent criteria. We propose a schedulability analysis generic for all policies within this class and evaluate other criteria by simulation. The study is illustrated in the framework of computer-controlled systems that are known to be sensitive to various delays induced by resource sharing

Anti-polyethylene glycol antibodies alter the protein corona deposited on nanoparticles and the physiological pathways regulating their fate in vivo

Multiple studies highlight the strong prevalence of anti-poly(ethylene glycol) (anti-PEG) antibodies in the general human population. As we develop therapeutic modalities using this polymer, it is increasingly relevant to assess the importance of anti-PEG antibodies on biological performances. Here, we show that the anti-PEG Immunoglobulin M (IgM) raised in mice following the injection of polymeric nanoparticles could have significant neutralizing effects on subsequent doses of PEGylated nanosystems in vivo. The circulation times of PEGylated nanoparticles and liposomes were strongly reduced in animals with circulating anti-PEG IgMs, irrespective of the PEG density or the surface properties of the system. In comparison, despite that anti-PEG IgMs could bind free methoxy-terminated PEG and PEGylated bovine serum albumin, the circulation kinetics of these systems remained unaltered in the presence of antibodies. The binding of IgMs to the PEGylated surface of nanoparticles alters the nature of the proteins adsorbed in the surrounding corona, notably due to the activation of the complement cascade. These changes are responsible for the observed differences in circulation times. In comparison, the PEG-BSA is unable to activate complement, even in the presence of anti-PEG IgMs. These results inform on how anti-PEG antibodies can affect the fate of PEGylated nanomaterials and highlight how the architecture of nanoparticles impacts the deposition of the protein corona

Pushing the limits of CAN - scheduling frames with offsets provides a major performance boost

International audienceWith the increasing amount of electronics, making best usage of the bandwidth becomes of primary importance in automotive networks. One solution that is being investigated by car manufacturers is to schedule the messages with offsets, which leads to a desynchronization of the message streams. As it will be shown, this “traffic shaping” strategy is very beneficial in terms of worst-case response times. In this chapter, the problem of choosing the best offsets is addressed in the case of Controller Area Network, which is a de-facto standard in the automotive world. Comprehensive experiments shown in this chapter give insight into the fundamental reasons why offsets are efficient, and demonstrate that offsets actually provide a major performance boost in terms of response times. These experimental results suggest that sound offset strategies may extend the lifespan of CAN further, and may defer the introduction of FlexRay and additional CAN networks

3D atom probe tomography of swift heavy ion irradiated multilayers

International audienceNanometer scale layered systems are well suited to investigate atomic transport processes induced by high-energy electronic excitations in materials, through the characterization of the interface transformation. In this study, we used the atom probe technique to determine the distribution of the different elements in an (amorphous-Fe$_2$Tb 5 nm/hcp-Co 3 nm)$_{20}$ multilayer before and after irradiation with Pb ions in the electronic stopping power regime. Atom probe tomography is based on reconstruction of a small volume of a sharp tip evaporated by field effect. It has unique capabilities to characterize internal interfaces and layer chemistry with sub-nanometer scale resolution in three dimensions. Depth composition profiles and 3D element mapping have been determined, evidencing for asymetric interfaces in the as-deposited sample, and very efficient Fe-Co intermixing after irradiation at the fluence $7\times10^{12}$ ion cm$^{-2}$. Estimation of effective atomic diffusion coefficients after irradiation suggests that mixing results from interdiffusion in a molten track across the interface in agreement with the thermal spike model