Applying the Powell's Symmetrical Technique to Conjugate Gradient Methods with the Generalized Conjugacy Condition

This article proposes new conjugate gradient method for unconstrained optimization by applying the Powell symmetrical technique in a defined sense. Using the Wolfe line search conditions, the global convergence property of the method is also obtained based on the spectral analysis of the conjugate gradient iteration matrix and the Zoutendijk condition for steepest descent methods. Preliminary numerical results for a set of 86 unconstrained optimization test problems verify the performance of the algorithm and show that the Generalized Descent Symmetrical Hestenes-Stiefel algorithm is competitive with the Fletcher-Reeves (FR) and Polak-Ribiére-Polyak (PRP⁺) algorithms.     

Modeling the sound transmission through complex structures with attached noise control materials

This paper discusses three extensions of the Transfer Matrix Method (TMM). The first deals with the modeling of the transmission loss of sandwich–composite panels. A wave based model is recalled and used to derive a simpler model based on identifying effective properties of an equivalent orthotropic panel. An experimental case study is presented to show the accuracy of these models when used to predict practical sound transmission problems involving single wall sandwich–honeycomb panels and double wall sandwich–honeycomb with an absorbing material filling the cavity between the two panels. In the second extension, the use of the TMM to predict the response of panels under various types of excitations is discussed. A wave based method is presented and compared with Finite Element Method (FEM) predictions for two types of excitations: Turbulent Boundary Layer (TBL) and point source. The comparison shows that the method allows for accurate predictions of the frequency averaged Transmission Loss (TL). Finally, the use of the TMM to model double wall systems with mechanical links is presented and numerically validated using FEM. It is found that the method captures well the decrease of the TL due to the insertion of the links and the effect of the excitation nature on this decrease.     

Estimation non paramétrique de la régression avec variable explicative dans un espace métrique

We study a nonparametric regression estimator when the explanatory variable takes its values in a semi-metric space. We establish some asymptotic results and give upper bounds of the p-mean and the almost sure estimation errors under general conditions. We end by an application to the discrimination in a semi-metric space and illustrate the results by the example of Wiener process as an explanatory variable. To cite this article: S. Dabo-Niang, N. Rhomari, C. R. Acad. Sci. Paris, Ser. I 336 (2003).     

Effect of cellulose crystallinity on bacterial cellulose assembly

Bacterial cellulose (BC) is a promising biomaterial as well as a model system useful for investigating cellulose biosynthesis. BC produced under static cultivation condition is a hydrous pellicle consisting of an interconnected network of fibrils assembled in numerous dense layers. The mechanisms responsible for this layered BC assembly remain unknown. This study used calcofluor as a fluorescent marker to examine BC layer formation at the air/liquid interface. Layers are found to move downward into the media after formation while new layers continue to form at the air/liquid interface. Calcoflour is also known to reduce the crystallinity of cellulose, changing the mechanical properties of the formed BC microfibrils. Consecutive addition and accumulation of calcofluor in the culture medium is found to disrupt the layered assembly of BC. BC crystalllinity decreased by 22 % in the presence of 12 % calcofluor (v/v) in the medium as compared to BC produced without calcofluor. This result suggests that cellulose crystallinity and the mechanical properties which crystallinity provides to cellulose are major factors influencing the layered BC structure formed during biosynthesis.     

Efficient purification and complete NMR characterization of galactinol,sucrose, raffinose,and stachyose isolated from Pinus halepensis (Aleppo pine) seeds using acetylation procedure

The use of precipitation followed by acetylation procedures and preparative TLC purification allowed a facile isolation of four carbohydrates from the methanol extract of Pinus halepensis seeds. The isolated oligosaccharides exhibited high degree of purity. They were identified as α-D-galactosyl-(1→1)-myo-inositol nonaacetate (1), α-D-glucosyl-(1→2)-β-D-fructosyl octaacetate (2), α-D-galactosyl-(1→6)-α-D-glucosyl-(1→2)-β-D-frutosyl undecaacetate (3), and α-D-galactosyl-(1→6)-α-D-galactosyl-(1→6)-α-D-glucosyl-(1→2)-β-D-frutosyl tetradecaacetate (4) and were isolated for the first time from this plant. The ¹H and ¹³C NMR assignments for compounds 2, 3, and 4 were detailed herein for the first time.     

Mechanical,thermal, and UV‐shielding behavior of silane surface modified ZnO‐reinforced phthalonitrile nanocomposites

In the present work, zinc oxide nanoparticles were treated with aminopropyl trimethoxy silane‐coupling agent and used as a new kind of reinforcement for a typical high performance bisphenol‐A‐based phthalonitrile resin. The resulted nanocomposites were characterized for their mechanical, thermal, and optical properties. Results from the tensile test indicated that the tensile strength and modulus as well as the toughness state of the matrix were all enhanced with the increasing of the nanoparticles amount. Thermogravimetric analysis showed that the starting decomposition temperatures and the residual weight at 800°C were highly improved upon adding the nanofillers. At 6 wt% nanoloading, the glass transition temperature and the storage modulus were considerably enhanced reaching about 359°C and 3.7 GPa, respectively. The optical tests revealed that the neat resin possesses excellent UV‐shielding properties, which were further enhanced by adding the nanofillers. Furthermore, the fractured surfaces of the nanocomposites analyzed by scanning electron microscope exhibited homogeneous and rougher surfaces compared with that of the pristine resin. Finally, the good dispersion of the reinforcing phase into the matrix was confirmed by a high resolution transmission electron microscope. Copyright © 2015 John Wiley & Sons, Ltd.     

Ab initio calculation of the electronic structure of the strontium hydride ion (SrH+)

The potentials, spectroscopic properties and electric dipole moments of SrH⁺ are computed for 63 molecular states dissociating up to Sr²⁺ + H^? using an ab initio approach. The ab initio formalism is based on large basis sets, nonempirical atomic pseudopotential for strontium core, correlation treatment for core valence through the effective core polarization potentials and for valence through full valence configuration interaction. Our theoretical molecular constants match published values very well and a large amount of new results is produced. Unusual potential shapes are found in ¹Σ⁺ states often caused by avoided crossing series between them and imprinted by the ionic state Sr²⁺H^?. The high potential energy curves suggest, it is possible to form H^? or at least to neutralize H⁺ in collisions with strontium. © 2014 Wiley Periodicals, Inc.     

Influence of iterated Gram–Schmidt orthonormalization in the asymptotic numerical methodInfluence de l'orthonormalisation itérative de Gram–Schmidt dans la méthode asymptotique numérique

In this paper we discuss the influence of Gram–Schmidt orthonormalization for the computation of the rational representation in the asymptotic numerical method. Classical, modified and iterated Gram–Schmidt algorithms are compared using the ordinary and the mass scalar products. The accuracy of the proposed algorithms are tested on elastic shells. To cite this article: R. Jamai, N. Damil, C. R. Mecanique 331 (2003).