Différentes voies de fonctionnalisation des fullerènes C60 et C70 et de nanotubes de carbone en vue d’applications photovoltaïques

Date du colloque&nbsp;: 10/2008</p

A robust orthogonal adaptive approach to SISO deconvolution

This paper formulates in a common framework some results from the fields of robust filtering, function approximation with orthogonal basis, and adaptive filtering, and applies them for the design of a general deconvolution processor for SISO systems. The processor is designed to be robust to small parametric uncertainties in the system model, with a partially adaptive orthogonal structure. A simple gradient type of adaptive algorithm is applied to update the coefficients that linearly combine the fixed robust basis functions used to represent the deconvolver. The advantages of the design are inherited from the mentioned fields: low sensitivity to parameter uncertainty in the system model, good numerical and structural behaviour, and the capability of tracking changes in the systems dynamics. The linear equalization of a simple ADSL channel model is presented as an example including comparisons between the optimal nominal, adaptive FIR, and the proposed design.Facultad de IngenieríaComisión de Investigaciones Científicas de la provincia de Buenos Aire

Error correcting code using tree-like multilayer perceptron

An error correcting code using a tree-like multilayer perceptron is proposed. An original message \mbi{s}^0 is encoded into a codeword \boldmath{y}_0 using a tree-like committee machine (committee tree) or a tree-like parity machine (parity tree). Based on these architectures, several schemes featuring monotonic or non-monotonic units are introduced. The codeword \mbi{y}_0 is then transmitted via a Binary Asymmetric Channel (BAC) where it is corrupted by noise. The analytical performance of these schemes is investigated using the replica method of statistical mechanics. Under some specific conditions, some of the proposed schemes are shown to saturate the Shannon bound at the infinite codeword length limit. The influence of the monotonicity of the units on the performance is also discussed.Comment: 23 pages, 3 figures, Content has been extended and revise

New cyclopropano 70 fullerene derivatives for the photovoltaic application

New cyclopropano 70 fullerenes derivatives were synthesised for photovoltaic (PV) application. The organic PV cells realized with these molecules blended with RR-P3HT polymer provided improved characteristics: 1.5% conversion efficiency (eta%), 9.29 mA/cm2 current density, 0.51 V open circuit voltage and 0.34 fill factor. The IPCE spectrum for P3HT: cyclopropano 70 fullerene cells shows a new peak around 430 nm with 71% external quantum efficiency. This explains the increased current density

In vitro calcification of chemically functionalized carbon nanotubes

Bone is composed of two phases. The organic phase is made of collagen fibrils assembled in broad fibers acting as a template for mineralization. The mineral phase comprises hydroxyapatite (HAP) crystals grown between and inside the collagen fibers. We have developed a biomimetic material using functionalized carbon nanotubes as scaffold to initiate in vitro mineralization. Biomimetic formation of HAP was performed on single-walled carbon nanotubes (SWCNTs) which have been grafted with carboxylic groups. Two types of nanotubes, HiPco(R) and Carbon Solutions(R), were oxidized via various acidic processes, leading to five different groups of carboxylated nanotubes, fully characterized by physical methods (thermogravimetric analysis, attenuated total reflectance infrared spectroscopy and X-ray photoelectron spectroscopy). All samples were dispersed in ultra-pure water and incubated for 2weeks in a synthetic body fluid, in order to induce the calcification of the SWCNTs. Scanning electron microscopy (SEM) and energy-dispersive X-ray analysis studies showed that Ca(2+) and PO(4)(3-) ions were deposited as round-shaped nodules (calcospherites) on the carboxylated SWCNTs. Fourier transform infrared and Raman spectroscopic studies confirmed the HAP formation, and image analysis made on SEM pictures showed that calcospherites and carboxylated SWCNTs were packed together. The size of calcospherites thus obtained in vitro from the HiPco(R) series was close to that issued from calcospherites observed in vivo. Functionalization of SWCNTs with carboxylic groups confers the capacity to induce calcification similar to woven bone

Carboxylated and esterified SWCNTs : characterization and contribution as components of biomaterials and solar cells

Date du colloque&nbsp;: 04/2010</p

Experimental measuring procedure for the friction torque in rolling bearings

The reduction of the power loss generated in mechanical transmissions and the use of low friction biodegradable lubricants has been attracting considerable attention in recent times. Therefore, it is necessary to develop methods to test and evaluate the performance of such lubricants and compare them with conventional ones. In this sense, a Four-Ball Machine was modified allowing the test of rolling bearings. A 51107 thrust ball bearing was used to test two different greases and the corresponding base oils. Friction torque and operating temperatures were continuously monitored to quantify the power loss and the heat evacuation for each lubricant tested. Copyright (C) 2010 John Wiley & Sons, Ltd