Geometrical shape optimization in fluid mechanics using FreeFem++

Structural and Multidisciplinary Optimization - In this article, we present simple and robust numerical methods for two-dimensional geometrical shape optimization problems, in the context of...     

On "Over-Sized" High-Gain Practical Observers for Nonlinear Systems

In this paper, it is shown that the performances of a class of high-gain practical observers can be improved by estimating the time derivatives of the output up to an order that is greater than the dimension of the system, which is assumed to be in observability form and, possibly, time-varying. Such an improvement is achieved without increasing the gain of the observers, thus allowing their use in a wide variety of control and identification applications.      

Boolean network representation of a continuous-time system and finite-horizon optimal control: application to the single-gene regulatory system for the lac operon

In this paper, the single-gene regulatory system for the lac operon is considered and a method to build a Boolean network able to represent its dynamics is given. A procedure, based on techniques borrowed from algebraic geometry, to compute an optimal control policy minimising a cost function is given for such a Boolean network. A tool to apply such an optimal control policy to the continuous-time system is reported. The proposed control method is tested in two simulative examples.     

Efficient implementation of Jacobi iterative method for large sparse linear systems on graphic processing units

In this paper, an original Jacobi implementation is considered for the solution of sparse linear systems of equations. The proposed algorithm helps to optimize the parallel implementation on GPU. The performance analysis of GPU-based (using CUDA) algorithm of the implementation of this algorithm is compared to the corresponding serial CPU-based algorithm. Numerical experiments performed on a set of matrices arising from the finite element discretization of various equations (3D Laplace equation, 3D gravitational potential equation, 3D Heat equation) with different meshes, illustrate the performance, robustness and efficiency of our algorithm, with a speed up to 23\(\times \) in double-precision arithmetics.     

Main recent contributions to SHS from France

Both in situ TRXRD and IR thermography, on the one hand, and different levels of modeling, on the other, have generated a strong progress in the knowledge and control of numerous SHS reactions. The SHS of simple binary materials, such as intermetallics (FeAl, MoSi₂, NbAl₃, etc.), oxides (e.g. ZrO₂), carbides (e.g. SiC) or nitrides, more complex materials, such as mullite, SiAlONs, MAX phases, composites (SiO₂-Al₂O₃, NiAl-ZrO₂), powders in their more complicated states, such as well controlled microstructures, fully densified intermetallics, smart composites, and hard coatings carried out by GFA researchers greatly contributed to the worldwide competition to harness the potential of SHS. On the occasion of the 40th anniversary of SHS, this paper is giving an overview of the main results obtained by GFA over the last ten years. Dominique Vrel (LIMHP UPR 1311 CNRS-Paris XIII, Villetaneuse)     

Evaluation of Surface Acido-Basic Properties of Inorganic-Based Solids by Model Catalytic Alcohol Reaction Networks

The characterization of acido-basic properties of the surface of inorganic solids is essential to understand the behavior of catalysts during heterogeneous catalyzed reactions. The use of alcohols as reactive probe molecules to investigate these properties has been developed since the 1970s, and in 1991, a new alcohol, 2-methylbut-3-yn-2-ol (MBOH), was proposed. This review sums up the knowledge accumulated for 15 years on this model reaction network and compares its advantages with those of other alcohols. The operating conditions are reviewed, and deactivation phenomena are analyzed. Then, from investigations of correlations with other techniques able to reveal the acido-basic properties of surfaces, it is concluded that MBOH appears to be the most valuable reactive probe molecule as the nature of the sites involved in the different routes of its network is unambiguous. The links that may exist between the rate of a model reaction and the thermodynamic acido-basic properties of the surface are then discussed. It is shown that even when true kinetics parameters are available, they are not necessarily correlated to thermodynamic parameters. What can be expected from a model reaction network is to evaluate the reactivity of a surface along an acidic or a basic route. In basic sites, this reactivity may be related to the nucleophilicity of the surface or to the way the deprotonated intermediate is stabilized on the surface. It can be used to follow the modifications of a series of materials during synthesis and to identify the factors governing a reaction of practical interest.     

Microwave-assisted extraction kinetics of terpenes from caraway seeds

The process conditions during the extraction of carvone and limonene from caraway seed (Carum carvi L.) with microwave-assisted extraction have been studied with respect to microwave power, radiation dose and extraction time in order to obtain the secondary metabolites selectively. Using classical solid–liquid extraction, limonene, carvone and fatty oils in both the raw material and the residual matrix material were extracted. Yields of limonene, carvone and total oil (C₁₆, C₁₈) were determined by GC and GC/MS analysis for both extracts. The effects of microwaves on cell walls and cells destruction could be seen on SEM micrographs.     

Enniatins fromFusarium avenaceum isolated from balsam fir foliage and their toxicity to spruce budworm larvae,Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae)

Material extracted from hyphae ofFusarium avenaceum, isolated from foliage of balsam fir,Abies balsamea, was toxic to spruce budworm larvae when incorporated into insect diet. The major insecticidal component of the toxic fraction was identified by chemical and spectroscopic methods as enniatin complex, rich in enniatin A/A₁. Possible ecological implications of these observations are considered.     

Ceramide structure of sphingomyelin from human milk fat globule membrane

Sphingomyelin was purified from human milk fat globule membrane and submitted to phospholipase C to yield ceramide. The structure of this ceramide was investigated by gas liquid chromatographic analyses of its components, fatty acids and sphingoid bases. The structure of the native ceramide was confirmed by direct-inlet mass spectrometry. It was shown to contain a major base C₁₈-sphingosine associated with a high proportion (60%) of C₂₀, C₂₂, C₂₄ and C_24∶1 nonhydroxylated fatty acids. As these very long-chain fatty acids might be of nutritive importance, the concentration of sphingomyelin in human milk and its distribution in cream and skim milk were established.