A GaAs MMIC chip-set for 10 to 15GHz radio-links applications

This paper describes the development of a GaAs MMIC chip-set for Ku-band radio-links transmitter. This chip-set includes two circuits, a times-two multiplier 5-7.5GHz to 10-15GHz, and a single side band up-converter. The development and the results of these circuits are analysed. The times-two multiplier is based on a specific balanced configuration leading to a very high level of input frequency suppression at the output (typically 50dBc) on a 2.7mm² chip. The mixer circuit is a broadband build-in single side band mixer of 10mm², with typically 30dBc image suppression

Electrical controlled rheology of a suspension of weakly conducting particles in dielectric liquid

The properties of suspensions of fine particles in dielectric liquid (electrorheological fluids) subjected to an electric field lead to a drastic change of the apparent viscosity of the fluid. For high applied fields (~ 3-5 kV/mm) the suspension congeals to a solid gel (particles fibrillate span the electrode gap) having a finite yield stress. For moderate fields the viscosity of the suspension is continuously controlled by the electric field strength. We have roposed that in DC voltage the field distribution in the solid (particles) and liquid phases of the suspension and so the attractive induced forces between particles and the yield stress of the suspension are controlled by the conductivities of the both materials. In this paper we report investigation and results obtained with nanoelectrorheological suspensions: synthesis of coated nanoparticles (size ~ 50 to 600 nm, materials Gd2O3:Tb, SiOx...), preparation of ER fluids (nanoparticles mixed in silicone oil), electrical and rheological characterization of the ER fluids. We also propose a possible explanation of the enhanced ER effect (giant ER fluids) taking into account the combined effects of the (nano)size of the particles, the Van der Waals forces between particles in contact and the electrostatic pressure in a very thin layer of insulating liquid.Comment: Article pour la conf\'{e}rence sur les charges d'espaces (CSC 6\`{e}me \'{e}dition) qui s'est d\'{e}roul\'{e}e \`{a} Tours du 3 au 7 juillet 2006. 6page

Best LpL_p Isotonic Regressions, p∈{0,1,∞}p \in \{0, 1, \infty\}

Given a real-valued weighted function $f$ on a finite dag, the $L_p$ isotonic regression of $f$, $p \in [0,\infty]$, is unique except when $p \in [0,1] \cup \{\infty\}$. We are interested in determining a ``best'' isotonic regression for $p \in \{0, 1, \infty\}$, where by best we mean a regression satisfying stronger properties than merely having minimal norm. One approach is to use strict $L_p$ regression, which is the limit of the best $L_q$ approximation as $q$ approaches $p$, and another is lex regression, which is based on lexical ordering of regression errors. For $L_\infty$ the strict and lex regressions are unique and the same. For $L_1$, strict $q \scriptstyle\searrow 1$ is unique, but we show that $q \scriptstyle\nearrow 1$ may not be, and even when it is unique the two limits may not be the same. For $L_0$, in general neither of the strict and lex regressions are unique, nor do they always have the same set of optimal regressions, but by expanding the objectives of $L_p$ optimization to $p < 0$ we show $p{ \scriptstyle \nearrow} 0$ is the same as lex regression. We also give algorithms for computing the best $L_p$ isotonic regression in certain situations