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Molecular desorption by a moving contact line
Get PDFThe interaction of the contact line with topographical or chemical defects at the nanometer scale sets the macroscopic wetting properties of a liquid on a solid substrate. Based on specific atomic force microscopy (AFM) experiments, we demonstrate that molecules physically sorbed on a surface are removed by a dynamic contact line. The mechanism of molecules desorption is directly determined by the capillary force exerted at the contact line on the molecules. We also emphasize the potential of AFM to clearly decorrelate the effects of topographical and chemical defects and monitor, with a subsecond time resolution, the dynamics of molecules adsorption on a surface
From Lustre to Simulink: reverse compilation for verifying Embedded Systems Applications
Get PDFModel-based design is now unavoidable when building embedded systems and more specifically controllers. Among the available model languages, the synchronous dataflow paradigm, as implemented in languages such as Matlab Simulink or ANSYS Scade, has become predominant in the critical embedded system industries. Both of these frameworks are used to design the controller itself but also provide code generation means, enabling faster deployment to target and easier V\&V activities performed earlier in the design process, at model level.
Synchronous models also ease the definition of formal specification through the use of synchronous observers, attaching requirements to the model in the very same language, mastered by engineers and tooled with simulation means or code generation.
However, few works address the automatic synthesis of Matlab Simulink annotations from lower level models or code. We present here a compilation process from Lustre models to genuine Matlab Simulink, without the need to rely on external C functions or Matlab functions. This re-engineering is then used to validate a compilation tool-chain, mapping Simulink to Lustre and then C, thanks to equivalence testing and checking. This backward-compilation from Lustre to Simulink also provides the ability to produce automatically Simulink components modeling specification, proof arguments or test cases coverage criteria
Beyond surface nanoindentation: Combining static and dynamic nanoindentation to assess intrinsic mechanical properties of chemical vapor deposition amorphous silicon oxide (SiOx) and silicon oxycarbide (SiOxCy) thin films
Get PDFNanoindentation is a well-known technique to assess the mechanical properties of bulk materials and films. Despite that, nanoindentation of thin films is not straightforward, given that the measured properties are composite information from a film/substrate system and depend on the indentation depth. By using dynamic indentation experiments and analytical or empirical models, we assessed the intrinsic film properties of chemical vapor deposited silicon oxide (SiOx) and silicon oxycarbide (SiOxCy) thin films with thicknesses ranging from 60 to 700 nm. In this work, the Bec rheological model and several mixing laws were reviewed. Measured Young modulus appeared to be affected by the substrate properties more than hardness: for the thinnest films, moduli were measured at ca. 90 GPa whereas intrinsic moduli were calculated at ca. 50 GPa. Using calculated intrinsic film modulus and hardness, it was possible to establish correlations between these properties, the chemical composition and the structural organization of the films
Fluid inertia effects on the motion of small spherical bubbles or solid spheres in turbulent flows
Get PDFIn this paper we study finite particle Reynolds number effects up to Re p=50 on the dynamics of small spherical bubbles and solid particles in an isotropic turbulent flow. We consider direct numerical simulations of light pointwise particles with various expressions of the drag force to account for finite Re p and the type of particle. Namely, we consider the Stokes drag law, the Schiller and Neumann relation and the Mei law. We show that an effective Stokes number, based on the mean value of the drag coefficient to account for the inertial effects involved in the drag law, gives a quasi-self-similar evolution of the variances of the bubble acceleration and of the forces exerted on the particle. This allows us to provide a satisfactory prediction of these quantities using Tchen's theory at finite particle Reynolds number. Based on these relations, we can specify the conditions under which the total inertial force (sum of the added mass and the Tchen contributions) is negligible compared with the drag force. Thus, for particles of very small dimensions, the fluid inertia force is negligible, provided the density ratio is of order 1 or larger. However, when the particle inertia becomes consequential, the threshold value of the density ratio increases significantly. Although this corresponds to the limit of the validity of the model, this draws attention to the fact that, for large Stokes numbers, the added mass and fluid inertia forces could play a more important role than is usually attributed to them
Qualitative and Quantitative Analysis of Avionics Full DupleX Network Models
No full textThe Avionics Full DupleX (AFDX) is a redundant and
reliable Ethernet network that ensures deterministic
communication. Unlike papers that exclusively address
AFDX with performance evaluation in mind, this pa-
per use both quantitative and qualitative analysis to
characterize the transmission of flows in the network.
Qualitative analysis enables checking the SysML model
of the network against temporal constraints. Quantita-
tive analysis uses a simulation approach to evaluate the
timing performances of the network
Enhancing Engineering Project Management Through Process Alignment
Get PDFIn order to lead successful projects, coordinating the different business units of a company is compulsory. This paper proposes a framework to make companies’ practices evolve toward a better alignment of the business units based on their processes, and illustrates it with project management and systems engineering processes. Indeed, all the different organisation units intend to serve the common global objective to satisfy the customer needs, and need to closely collaborate during projects. However, work organization in companies often leads to barriers between these stakeholders, with the result of an incoherent decision-making that may compromise project execution. Therefore, the issue of processes alignment from different domains lies at the very heart of ongoing research topics and ranks first among economic and industrial concerns. This paper uses a qualitative approach to show how different business units’ processes can be integrated and illustrate this framework by aligning the systems engineering and project management processes within a certain engineering project context. By using the proposed framework, different teams (or even different companies, in a context of distributed enterprise) can align their practices, while also making them evolve toward a better compliance with standards
Verifying the Mathematical Library of an UAV Autopilot with Frama-C
Get PDFEnsuring safety of critical systems is crucial and is often attained by extensive testing of the system. Formal methods are now commonly accepted as powerful tools to obtain guarantees on such systems, even if it is generally not possible to formally prove the safety and correctness of the whole system. This paper presents an ongoing work on the formal verification of the Paparazzi UAV autopilot using the Frama-C verification platform. We focus on a Paparazzi mathematical library providing different UAV state representations and associated conversion functions and manage to prove the absence of runtime errors in the library and some interesting functional properties on floating-point conversion functions
Path planning control using high abstraction level environment model and industrial taskoriented knowledge
Get PDFIn order to face an increasing economic competition, industrial manufacturers wish to reduce the time and cost of product development. Furthermore, up-to-date products are more and more integrated, and must be assembled, disassembled or maintained under potentially very strong geometric constraints. In the context of Industry 4.0, manufacturers are therefore expressing the desire to validate all the tasks related to their products lifecycles, from design stage on, by simulation using a digital mock-up, and before building the physical prototypes. A key issue is then to find a trajectory, a movement, to show the feasibility of the simulated scenarios. Automatic path planning algorithms, developed by the robotics community from the 1980s on, have been widely used for this purpose. In this paper, we intend to improve the relevance of the trajectories proposed by such algorithms and the associated computation times. To do so, we consider: a) the use of path planning algorithms or of combinations of these; b) the involvement for the environment modelling of data with a higher abstraction level than the purely geometric data traditionally used; and c) the representation of the knowledge
related to the task to be performed by using ontologies. The approaches developed and associated improvements of the state of the art are validated experimentally through the simulation of highly geometrically constrained manipulation tasks
Dynamique des résistances aux anthelminthiques chez les strongles gastro-intestinaux dans deux estives ovines pyrénéennes
Get PDFLe test de réduction de l’excrétion fécale (FECRT) a été utilisé pour évaluer la présence de résistances aux anthelminthiques, dans 6 élevages composant une estive des Hautes-Pyrénées, avant la montée et après la descente des animaux de la zone d’estive. Un protocole similaire a été mis en place au sein de 5 élevages, composant une estive en Ariège. Cependant dans ce cas la dynamique des résistances n’a pas pu être étudiée. Dans ces élevages, selon le nombre d’animaux disponibles, 1 à 6 molécules ont été testées : le fenbendazole, le lévamisole, l’ivermectine, la moxidectine, le monépantel et le closantel. Des coprocultures et une identification des larves obtenues par qPCR ont été réalisées. Au sein de tous les élevages, une résistance au fenbendazole a été mise en évidence. Pour 10 élevages des 11 élevages participants, elle concernait H.contortus, T. circumcinta et T. colubriformis. Le lévamisole, l’ivermectine et la moxidectine, semblent encore globalement efficaces, bien que pour chacune d’elles, des élevages montrant une perte d’efficacité aient été détecté. Le closantel et le monepantel n’ont pas montré de résistances. Il semblerait qu’une population de H. contortus résistante à l’ivermectine ait pu être transmise entre deux élevages des Hautes- Pyrénées, au cours de l’estive
Unsteady Body Force Methodology for Fan Operability Assessment under Clean and Distorted Inflow Conditions
Get PDFWith more complex aircraft architectures, fast and cost-effective design iterations are key to improve overall fuel efficiency. This paper proposes to revisit a low-order unsteady modeling approach to replace costly full annulus URANS simulation. Unsteady Body Force Methods (UBFM) could allow a significant cost reduction for fan distortion ingestion and operability assessment. In this approach, the bladed area in the computational domain is replaced by source terms in the Navier–Stokes equations, and the cost of the simulation is reduced by a factor of 26. The operability of the fan is evaluated with and without distortion in order to assess the accuracy of the model. Previously published results of URANS simulations performed on the same fan subject to an unsteady vortex ingestion are used as reference.1 The results show that our UBFM is able to predict rotating stall cells, with patterns and rotating speed similar to the URANS data