Le public et ses problèmes : le problème social de la connaissance

International audienceThe Public and its problems paraît en 1927 deux ans après l’ouvrage de W. Lippmann The Phantom Public. (...

Optimization of Band Pass Delta Sigma modulators using parameters identification

International audienceIn this paper, a method to study and characterize a single-loop, cascaded and 1-bit band-pass delta sigma (BPΔΣ) modulator for digital transmitter is presented. This technique is based on a combination of digital filter simulation and nonlinear optimization of signal-to-quantization noise. The optimal coefficients of BPΔΣ structure are achieved by minimization of a quadratic criterion based on prediction error between desired digital filter and noise transfer model. To demonstrate the effectiveness of this approach, simulated results for a 6th order cascaded structure for WCDMA band-1 standard are presented

Characterization of BandPass Delta Sigma Modulators in Wireless Transceivers Using Parameter Identification

International audienceIn this paper, a method to study and characterize a single-loop, cascaded and 1-bit Band-Pass Delta Sigma modulator for digital transmitter is presented. This technique is based on a combination of digital filter simulation and nonlinear optimization of signal-to-quantization noise. The optimal coefficients of modulator structure are achieved by minimization of a quadratic criterion based on prediction error between desired digital filter and noise transfer model. To demonstrate the effectiveness of this approach, simulated results for a sixth order cascaded structure for WCDMA Band-1 standard are presented. Spurious and ACLR improvement could be achieved for this standard with the proposed characterization technique

Imaging of Early-Stage Cracking on Real-Size Concrete Structure from 4-Points Bending Test

International audienceTraditional ultrasonic imaging techniques encounter difficulty on complexes material such as concrete, which is in part due the use of coherent waves in a very heterogeneous material. From this angle, technique called LOCADIFF has been developed for monitoring heterogeneous media using multiply scattered waves [1, 2]. We consider that modifications in the medium are equivalent to the presence of extra scatterers, which are characterized by their effective scattering cross-section &#963,. Within this view, LOCADIFF allows to locate the modification by measuring the spatio-temporal de-correlation of multiply scattered waves and by solving the corresponding inverse problem. Based on LOCADIFF, a newly developed imaging technique has been reported [3]. By mapping the intensity of modification on localized microstructure, the new technique is able to detect perturbations at multiple locations. Here we present the application of this new technique on a real-size 15 tons concrete structure for imaging early-stage cracking procedure issued from four point bending load, as part of the CEOS.fr project. Experimental results show that this technique can not only locate cracks that appeared simultaneously at multiple locations, but also detect them and observe their developments since an early-stage

Bandpass delta sigma optimization using parameter identification

International audienceIn this paper, a new method to optimize the noise shape of a bandpass delta sigma (BPDS) modulator for a digital transmitter is presented. The optimal coefficients of BPDS structure are obtained by minimization of a quadratic criterion based on prediction error. To demonstrate the effectiveness of this approach, simulated results for a 6th order BPDS structure are presented

Improved Delta Sigma Modulators for High Speed Applications

International audienceThis article presents a new Low-Pass Delta Sigma Modulators (LPDS) architecture to improve the noise shaping for high frequency applications. The errors resulting from approximations made by calculating with 1/2N coefficients are compensated. Simulations with extracted parasitics of the layout are made and give a SNDR of 111 dB, 3.8 mW power consumption at 4 GHz in 65 nm CMOS technology for UMTS standard

Modelling ballast behaviour under dynamic loading. Part 1: A 2D polygonal discrete element method approach

International audienceDiscrete element simulation provides some insight into the alteration of railway ballast after repeated train passings. The present Part 1 is devoted to a 2D model of this granular layer interposed between the deformable ground and the rail sleeper, to which a large number of loading cycles is applied. Ballast grains are modelled as indeformable polygonal solids. A detailed account of the application to this frictional dynamical problem of the Non-Smooth Contact Dyna- mics numerical method is given. Validation is obtained through comparison with physical experiments performed on assemblies of prismatic mineral grains. Numerical results on the settlement of a track submitted to 20,000 loading cycles or more are presented

Polarized distribution of inducible nitric oxide synthase regulates activity in intestinal epithelial cells

Inducible nitric oxide synthase (iNOS) functions as a homodimer. In cell extracts, iNOS molecules partition both in cytosolic and particulate fractions, indicating that iNOS exists as soluble and membrane associated forms. In this study, iNOS features were investigated in human intestinal epithelial cells stimulated with cytokines and in duodenum from mice exposed to flagellin. Our experiments indicate that iNOS is mainly associated with the particulate fraction of cell extracts. Confocal microscopy showed a preferential localization of iNOS at the apical pole of intestinal epithelial cells. In particulate fractions, iNOS dimers were more abundant than in the cytosolic fraction. Similar observations were seen in mouse duodenum samples. These results suggest that, in epithelial cells, iNOS activity is regulated by localization-dependent processes.Facultad de Ciencias Exacta