Insonorisation of a car air conditionning system: application of an active/passive absorber

this work is part of a project examining the implementation of active noise control in a car air conditionning system. In our system, a part of the problem is related to the flow itself. Indeed, the more the duct system geometry is complex, the more the internal flow is disturbed, leading to a high degree of turbulence. So the signal spectrum recorded by the microphone is the sum of this uncorrelated turbulent signal and the true noise signal. Taking into account these considerations, the purpose of the present work is to find the best strategy in order to cancel the noise coming from a centrifugal fan using active noise control on a real air conditionning system. Some real time tests in the car air conditionning system are finally presented

Barriers to the care of HIV-infected children in rural Zambia: a cross-sectional analysis

<p>Abstract</p> <p>Background</p> <p>Successful antiretroviral treatment programs in rural sub-Saharan Africa may face different challenges than programs in urban areas. The objective of this study was to identify patient characteristics, barriers to care, and treatment responses of HIV-infected children seeking care in rural Zambia.</p> <p>Methods</p> <p>Cross-sectional analysis of HIV-infected children seeking care at Macha Hospital in rural southern Zambia. Information was collected from caretakers and medical records.</p> <p>Results</p> <p>192 HIV-infected children were enrolled from September 2007 through September 2008, 28% of whom were receiving antiretroviral therapy (ART) at enrollment. The median age was 3.3 years for children not receiving ART (IQR 1.8, 6.7) and 4.5 years for children receiving ART (IQR 2.7, 8.6). 91% travelled more than one hour to the clinic and 26% travelled more than 5 hours. Most participants (73%) reported difficulties accessing the clinic, including insufficient money (60%), lack of transportation (54%) and roads in poor condition (32%). The 54 children who were receiving ART at study enrollment had been on ART a median of 8.6 months (IQR: 2.7, 19.5). The median percentage of CD4⁺T cells was 12.4 (IQR: 9.2, 18.6) at the start of ART, and increased to 28.6 (IQR: 23.5, 36.1) at the initial study visit. However, the proportion of children who were underweight decreased only slightly, from 70% at initiation of ART to 61% at the initial study visit.</p> <p>Conclusion</p> <p>HIV-infected children in rural southern Zambia have long travel times to access care and may have poorer weight gain on ART than children in urban areas. Despite these barriers, these children had a substantial rise in CD4⁺T cell counts in the first year of ART although longer follow-up may indicate these gains are not sustained.</p

Determining adsorbate configuration on alumina surfaces with 13C nuclear magnetic resonance relaxation time analysis

Relative strengths of surface interaction for individual carbon atoms in acyclic and cyclic hydrocarbons adsorbed on alumina surfaces are determined using chemically resolved 13C nuclear magnetic resonance (NMR) T1 relaxation times. The ratio of relaxation times for the adsorbed atoms T1,ads to the bulk liquid relaxation time T1,bulk provides an indication of the mobility of the atom. Hence a low T1,ads/T1,bulk ratio indicates a stronger surface interaction. The carbon atoms associated with unsaturated bonds in the molecules are seen to exhibit a larger reduction in T1 on adsorption relative to the aliphatic carbons, consistent with adsorption occurring through the carbon-carbon multiple bonds. The relaxation data are interpreted in terms of proximity of individual carbon atoms to the alumina surface and adsorption conformations are inferred. Furthermore, variations of interaction strength and molecular configuration have been explored as a function of adsorbate coverage, temperature, surface pre-treatment, and in the presence of co-adsorbates. This relaxation time analysis is appropriate for studying the behaviour of hydrocarbons adsorbed on a wide range of catalyst support and supported-metal catalyst surfaces, and offers the potential to explore such systems under realistic operating conditions when multiple chemical components are present at the surface

Contribution a l'etude des catalyseurs Pd-silice et Pd-zeolithes

SIGLEAvailable from INIST (FR), Document Supply Service, under shelf-number : TD 78152 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc

Dynamique et stratégies d'équipes au service d'un climat d'école positif

Ce mémoire aspire à mesurer l'efficacité d'un des leviers de prévention et de lutte contre les violences scolaires en école primaire. La recherche montre que la coopération entre équipes scolaires et périscolaires a un impact positif sur le sentiment de justice des élèves, sur le climat relationnel et le climat d'école. Ainsi, la problématique de cette étude questionne l'influence de la dynamique et des stratégies d'équipes sur le climat scolaire. Pour y répondre, une analyse comparative a été réalisée à partir de questionnaires à destination de professionnels et d'élèves. Il s'agissait de mesurer l'effet du travail en équipes sur différents axes du climat scolaire. Les résultats indiquent que la coopération au sein des acteurs de l'école influence positivement le sentiment de justice des élèves, leur perception du climat relationnel au sein de l'école, et permet une mutualisation pluri-professionnelles favorable à un climat d'école propice au bien-être et aux apprentissages

Etude échographique des enthèses et des petites articulations des mains et des pieds chez l'enfant

BREST-BU Médecine-Odontologie (290192102) / SudocPARIS-BIUM (751062103) / SudocSudocFranceF