Viscosity of multimodal suspensions predicted from solid fraction model for mixtures

International audienceObjectives: The model is able to predict the viscosity of a suspension of non colloidal rigid spherical particles in a Newtonian fluid. The theory is developed to highlight a new relation between relative viscosity and the solid volume fraction. A new version of the Compressible Packing Model (CPM), the 4-parameter CPM, is introduced to predict the solid fraction of maximally dense disordered packings of spherical particles. It is apt to account for the geometrical interactions between particles

The 4-parameter Compressible Packing Model (CPM) for sustainable concrete

International audienceTo reduce the environmental impact due to the CO 2-emission, it is necessary to optimize the concrete mix-design by reducing the amount of cement. In this case, analytical packing models are necessary to predict the packing density of a pile of grains. A new version of the Compressible Packing Model (CPM) (de Larrard et al.), the 4-parameter CPM, is introduced to predict the solid fraction of maximally dense disordered packings of bidisperse particles. It is apt to account for the loosening effect on big particles by interstitial small ones, and for the wall effect within assemblies of small particles near a big one, with moderate size ratios. The new theory is based on a specific treatment of configurations of one secondary class particle surrounded by dominant class neighbours. It has four parameters : wall effect and loosening effect coefficients, critical cavity size ratio and compaction index. The model proves its efficiency when compared to 780 results on various tested materials. The correlation coefficients between predicted and measured packing densities are very high: 99% for frictionless glass beads, 98,7% for spherical particles numerically simulated, 97,8% for natural aggregates and 96,4% for crushed aggregates. To predict the viscosity of the same grains in a high concentrated suspension compound of spherical, inert and rigid particles suspended in a Newtonian fluid, we resort to the iterative approach advocated by Farris and to the Krieger-Dougherty power-law relation for the relative viscosity. The theory was developed to highlight a new relation between relative viscosity and the solid volume fraction, compatible with Einstein's relation

Dataflow/Actor-Oriented language for the design of complex signal processing systems

Signal processing algorithms become more and more complex and the algorithm architecture adaptation and design processes cannot any longer rely only on the intuition of the designers to build efficient systems. Specific tools and methods are needed to cope with the increasing complexity of both algorithms and platforms. This paper presents a new framework which allows the specification, design, simulation and implementation of a system operating at a higher level of abstraction compared to current approaches. The framework is base on the usage of a new actor/dataflow oriented language called CAL. Such language has been specifically designed for modelling complex signal processing systems. CAL data flow models expose the intrinsic concurrency of the algorithms by employing the notions of actor programming and dataflow. Concurrency and parallelism are very important aspects of embedded system design as we enter in the multicore era. The design framework is composed by a simulation platform and by Cal2C and CAL2HDL code generators. This paper described in details the principles on which such code generators are based and shows how efficient software (C) and hardware (VHDL and Verilog) code can be generated by appropriate CAL models. Results on a real design case, a MPEG-4 Simple Profile decoder, show that systems obtained with the hardware code generator outperform the hand written VHDL version both in terms of performance and resource usage. Concerning the C code generator results, the results show that the synthesized C-software mapped on a SystemC scheduler platform, is much faster than the simulated CAL dataflow program and approaches handwritten C versions

Viscosité des suspensions multimodales concentrées dans un fluide Newtonien

International audienceA new theoretical formulation about the viscosity of a multimodal concentrated suspension of non-colloidal spherical rigid particles in a Newtonian fluid is presented: the relative viscosity can be linked both to the volume fraction of the suspended particles in a total volume unity and to the solid fraction of the dry mixture. Therefore, it takes into account hydrodynamic interactions and geometrical interactions between particles. Concerning the first ones, it resorts to an iterative approach by change of scale method according to the concept of Farris. Concerning the second ones, when the volume fraction of the suspended particles reaches its critical value, the suspension is jammed and the mixture reaches the solid fraction of the solid skeleton which is predicted by the Compressible Packing Model (CPM). This one takes into account both the loosening effect on big particles by interstitial small ones and the wall effect within assemblies of small particles near a big one. Our predicted viscosities are in good agreement with experimental data of relative viscosities obtained on binary mixtures with 3 different size ratios, for glass beads in silicone oil.Une nouvelle formulation théorique concernant une suspension concentrée multimodale de particules sphériques rigides non-colloïdales dans un fluide Newtonien est présentée: la viscosité relative peut être reliée à la fois à la fraction volumique des particules suspendues dans un volume total unité et à la compacité du mélange sec. Elle tient compte des interactions hydrodynamiques et des interactions géométriques entre particules. Concernant les premières, elle fait appel à une approche itérative de type changement d'échelle conformément au concept de Farris. Concernant les secondes, lorsque la fraction volumique des particules suspendues atteint sa valeur critique, la suspension devient empilement et le mélange atteint la compacité du squelette solide prédite par le Modèle d'Empilement Compressible (MEC). Celui-ci tient compte à la fois de l'effet de desserrement provoqué par les fines particules sur les grosses et de l'effet de paroi provoqué par ces dernières sur les plus petites. Nos viscosités calculées sont en bonne adéquation avec les viscosités relatives expérimentales obtenues sur des mélanges binaires avec 3 rapports de tailles différents, pour des billes de verre dans une huile de silicone

RVC: A multi-decoder CAL Composer tool

The Reconfigurable Video Coding (RVC) framework is a recent ISO standard aiming at providing a unified specification of MPEG video technology in the form of a library of components. The word “reconfigurable” evokes run-time instantiation of different decoders starting from an on-the-fly analysis of the input bitstream. In this paper we move a first step towards the definition of systematic procedures that, based on the MPEG RVC specification formalism, are able to produce multi-decoder platforms, capable of fast switching between different configurations. Looking at the similarities between the decoding algorithms to implement, the papers describes an automatic tool for their composition into a single configurable multi-decoder built of all the required modules, and able to reuse the shared components so as to reduce the overall footprint (either from a hardware or software perspective). The proposed approach, implemented in C++ leveraging on Flex and Bison code generation tools, typically exploited in the compilers front-end, demonstrates to be successful in the composition of two different decoders MPEG-4 Part 2 (SP): serial and parallel

MPEG reconfigurable video coding

The current monolithic and lengthy scheme behind the standardization and the design of new video coding standards is becoming inappropriate to satisfy the dynamism and changing needs of the video coding community. Such a scheme and specification formalism do not enable designers to exploit the clear commonalities between the different codecs, neither at the level of the specification nor at the level of the implementation. Such a problem is one of the main reasons for the typical long time interval elapsing between the time a new idea is validated until it is implemented in consumer products as part of a worldwide standard. The analysis of this problem originated a new standard initiative within the ISO/IEC MPEG committee, called Reconfigurable Video Coding (RVC). The main idea is to develop a video coding standard that overcomes many shortcomings of the current standardization and specification process by updating and progressively incrementing a modular library of components. As the name implies, flexibility and reconfigurability are new attractive features of the RVC standard. The RVC framework is based on the usage of a new actor/dataflow oriented language called CAL for the specification of the standard library and the instantiation of the RVC decoder model. CAL dataflow models expose the intrinsic concurrency of the algorithms by employing the notions of actor programming and dataflow. This chapter gives an overview of the concepts and technologies building the standard RVC framework and the non standard tools supporting the RVC model from the instantiation and simulation of the CAL model to the software and/or hardware code synthesis