Evaluation of the Shear Modulus in Models for Shallow-Foundation Dynamics within the Elastic Domain

The aim of this presentation is to examine the relationship of the equivalent homogeneous shear moduli used in impedance models with stresses under the footing, through the use of scaled models in the centrifuge and an impact loading. The analysis of time and frequency vertical responses of footings reveals that reflections on the boundaries are negligible. The frequency response of a series of circular and square footings is shown to be rather easily-fitted with Wolf’s models for foundations on an infinite half-space with reasonably consistent parameters for masses, damping and shear moduli. The damping is nearly constant, yet significantly lower than in a prototype scale with real soil. The mass is fitted with a greater level of scatter. The correlation of shear modulus to the square root of the minimum mean stress appears to be better than that to the square root of the uniform stress under the footing

Low-Dimensional Materials for Disruptive Microwave Antennas Design

This chapter is devoted to a complete analysis of remarkable electromagnetic properties of nanomaterials suitable for antenna design miniaturization. After a review of state of the art mesoscopic scale modeling tools and characterization techniques in microwave domain, new approaches based on wideband material parameters identification (complex permittivity and conductivity) will be described from impedance equivalence formulation achievement by de-embedding techniques applicable in integrated technology or in free space. A focus on performances of 1D materials such as vertically aligned multi-wall carbon nanotube (VA-MWCNT) bundles, from theory to technology, will be presented as a disruptive demonstration for defense and civil applications as in radar systems

Identification of Different Seismic Waves Generated by Foundation Vibration in the Centrifuge: Travel Time, Spectral and Numerical Investigations

For the analysis of footings under dynamic loading scaled modeling in the centrifuge assumes that the soil behaves like at prototype scale. This paper demonstrates that for a container filled with dry sand, wave velocities can be described by a model based on the relation between the shear modulus and the depth dependent stress level proposed by Iwasaki and Tatsuoka. A preliminary estimation of the shear wave velocities and of the Poisson’s ratio confirms by dynamical measurements the currently use value of 0.25. A FEM modeling also helps to strengthen the validity of the model proposed, providing another insight in the propagation of waves in a soil with a velocity gradient

Interaction Site-Ville : Approches expérimentales et numériques

À l’échelle d’une ville, les structures de surface telles que les bâtiments peuvent modifier le mouvement sismique en 'champ libre' et agir comme des sources sismiques secondaires. Des observations ont en particulier été réalisées sur des données réelles. Elles montrent que cet effet peut être significatif. La conséquence directe de cette 'interaction site-ville' est la pollution du mouvement sismique en milieu urbain par un champ d’onde secondaire. Des modélisations en centrifugeuse et numériques tendent à confirmer que ce phénomène n’est pas anecdotique. En particulier, ces résultats montrent qu’entre deux bâtiments proches des interactions existent, modifiant le mouvement du sol mais aussi la réponse des structures impliquées. À l’échelle d’une ville, ce phénomène sera d’autant plus marqué lorsqu’un fort couplage existe entre la réponse du sol et la réponse du milieu urbain

Tests of achromatic phase shifters performed on the SYNAPSE test bench: a progress report

The achromatic phase shifter (APS) is a component of the Bracewell nulling interferometer studied in preparation for future space missions (viz. Darwin/TPF-I) focusing on spectroscopic study of Earth-like exo-planets. Several possible designs of such an optical subsystem exist. Four approaches were selected for further study. Thales Alenia Space developed a dielectric prism APS. A focus crossing APS prototype was developed by the OCA, Nice, France. A field reversal APS prototype was prepared by the MPIA in Heidelberg, Germany. Centre Spatial de Li\`ege develops a concept based on Fresnel's rhombs. This paper presents a progress report on the current work aiming at evaluating these prototypes on the SYNAPSE test bench at the Institut d'Astrophysique Spatiale in Orsay, France

Opto-thermo-mechanical numerical simulations of 3 different concepts of infrared achromatic phase shifters

The Darwin/TPF mission aims at detecting directly extra solar planets. It is based on the nulling interferometry, concept proposed by Bracewell in 1978, and developed since 1995 in several European and American laboratories. One of the key optical devices for this technique is the achromatic phase shifter (APS). This optical component is designed to produce a π phase shift over the whole Darwin spectral range (i.e. 6-18 μm), and will be experimentally tested on the NULLTIMATE consortium nulling test bench (Labèque et al). Three different concepts of APS are being simulated: dispersive plates focus crossing and field reversal. In this paper, we show how thermal, mechanical and optical models are merged into a single robust model, allowing a global numerical simulation of the optical component performances. We show how these simulations help us to optimizing the design and present results of the numerical model

Marianne Mahn-Lot (1913-2005)

Chazelas Jean. Marianne Mahn-Lot (1913-2005). In: Bibliothèque de l'école des chartes. 2006, tome 164, livraison 2. pp. 681-684

Pierre GROSCLAUDE. Malesherbes. Témoin et interprète de son temps. Paris, Fischbacher, 1961.

Chazelas Jean. Pierre GROSCLAUDE. Malesherbes. Témoin et interprète de son temps. Paris, Fischbacher, 1961.. In: Bibliothèque de l'école des chartes. 1964, tome 122. pp. 339-344

J.-F FAURE-SOULET. Economie politique et progrès au "siècle des lumières". Préface de Paul HARSIN. Avant-propos d'André PIATTIER. Paris, Gauthier-Villars, 1964 (Coll. "Techniques économiques modernes", t. IV, série "Histoire et pensée économique" n°1.)

Chazelas Jean. J.-F FAURE-SOULET. Economie politique et progrès au "siècle des lumières". Préface de Paul HARSIN. Avant-propos d'André PIATTIER. Paris, Gauthier-Villars, 1964 (Coll. "Techniques économiques modernes", t. IV, série "Histoire et pensée économique" n°1.) . In: Bibliothèque de l'école des chartes. 1967, tome 125, livraison 1. pp. 274-275

Pierre GROSCLAUDE. Malesherbes. Témoin et interprète de son temps. Paris, Fischbacher, 1961.

Chazelas Jean. Pierre GROSCLAUDE. Malesherbes. Témoin et interprète de son temps. Paris, Fischbacher, 1961.. In: Bibliothèque de l'école des chartes. 1964, tome 122. pp. 339-344