361 research outputs found
Ingénierie cognitive pour l'aide à la conduite automobile de la personne ùgée : analyse et modélisation de l'activité de conduite en situation naturelle pour la conception de fonctions de monitorage
This thesis in Cognitics presents a Human Centered Design approach for thedevelopment of future driving assistance systems dedicated to elderly drivers orElderly Adapted Driver Assistance Systems (E-ADAS).To do so, this work relies on a multi-disciplinary approach for data collection andanalysis. Regarding Ergonomics, the aim is to better understand the specificrequirements of this population in order to identify their actual difficulties and actualneeds of assistance. In this frame, 76 drivers (aged from 70 to 87 years old) took partto an on-the-road experiment, driving an instrumented car. The dataset includes2100 km of ecological driving data and 1400 auto-evaluated driving situations,completed by 6 Focus Groups (involving 30 elderly drivers).The second part of this research, relying on Cognitive Engineering, explores thedesign and implementation of monitoring functions based on the aforementioneddataset. The objective is to have real-time models and analytical functions, able to:(1) supervise the driving activity as realized by an elderly driver, (2) taking in toconsideration the driving context or situational risks (3) in order to detect difficulties ordriving errors. Beyond this thesis, these diagnostics will have to be integrated inassistive systems to better adapt their support to the specific needs of elderly drivers.Specific monitoring functions related to basic vehicle control (speed management,lane positioning and headway regulation) are presented. Based on these results,integrated monitoring functions for intersection crossings in Left-Turn manoeuver,highway merging assistance, and, more broadly, lane change assistance areintroduced.Cette thĂšse en Cognitique se focalise sur la « Conception CentrĂ©e sur l'Humain » (Human Centred Design) de futures assistances Ă la conduite automobile, adaptĂ©es aux conducteurs ĂągĂ©s (ou Elderly Adapted Driver Assistance Systems).Pour ce faire, la dĂ©marche proposĂ©e repose sur une approche et une mĂ©thodologie pluridisciplinaire. Sur le plan ergonomique, il s'agit de mieux connaĂźtre les spĂ©cificitĂ©sde la population des conducteurs ĂągĂ©s, dans le but d'identifier des difficultĂ©s et des besoins en assistance. A cette fin, 76 conducteurs ĂągĂ©s (de 70 Ă 87 ans) ont conduitun vĂ©hicule instrumentĂ©, immergĂ© dans le trafic. Le corpus de donnĂ©es comporte2100 kilomĂštres de conduite et 1400 situations de conduite autoĂ©valuĂ©es par lesconducteurs, complĂ©tĂ©s par 6 Focus Group (30 conducteurs ĂągĂ©s).Le second volet, relevant d'une dĂ©marche d'IngĂ©nierie Cognitive, vise Ă concevoir et dĂ©velopper des fonctions de « monitorage » Ă partir du corpus de donnĂ©es. L'objectif est de disposer de modĂšles et de fonctions d'analyse temps-rĂ©el capables (1) de superviser l'activitĂ© de conduite des conducteurs ĂągĂ©s (2) en regard du contexte ou des risques situationnels, afin de (3) diagnostiquer des difficultĂ©s ou erreurs de conduite, Ă des fins dâadaptativitĂ© des assistances. Des fonctions de monitorage en lien avec les contrĂŽles de base du vĂ©hicule (gestion de la vitesse, positionnement dans la voie et la gestion de l'espace inter-vĂ©hiculaire avant) sont dĂ©veloppĂ©es. Sur cette base, des fonctions de monitorage plus intĂ©grĂ©es pour l'aide aux franchissements d'intersections (Tourne-Ă -Gauche) et l'assistance Ă l'insertion sur voies rapides (et au changement de voie) sont Ă©galement proposĂ©es
Primal-dual splitting algorithm for solving inclusions with mixtures of composite, Lipschitzian, and parallel-sum monotone operators
We propose a primal-dual splitting algorithm for solving monotone inclusions
involving a mixture of sums, linear compositions, and parallel sums of
set-valued and Lipschitzian operators. An important feature of the algorithm is
that the Lipschitzian operators present in the formulation can be processed
individually via explicit steps, while the set-valued operators are processed
individually via their resolvents. In addition, the algorithm is highly
parallel in that most of its steps can be executed simultaneously. This work
brings together and notably extends various types of structured monotone
inclusion problems and their solution methods. The application to convex
minimization problems is given special attention
Wear mechanisms of WC-Co drill bit inserts against alumina counterface under dry friction: Part 2 â Graded WC-Co inserts
The tribological behaviour of innovative graded cemented carbide inserts were studied by using a rotary tribometer and abrasive alumina counterfaces. This work completes the study made on commercial inserts with homogeneous cobalt content. Inserts with three types of graduation processes were considered: inserts with borides WCoB phases, imbibed inserts and inserts combining both processes (i.e. inserts with reactive imbibition). Physicochemical and mechanical measurements show that the WCoB phases increase the hardness towards the active surface and the imbibition increases the insert core fracture toughness. The wear tests indicate that the boride phases lower the friction coefficient. In addition, as for the commercial inserts, cemented carbide volumes with higher cobalt content also reduce the friction coefficient. Concerning the wear results, the boride phases improve the abrasion resistance. By applying a third body approach, the WCoB phases limit the introduction of cobalt binder in the source flow, the cohesion of alumina particles in the internal flow and the formation of an abrasive paste in the contact. The imbibition process, where the cobalt migration is controlled, does not affect the wear resistance by avoiding a cobalt enrichment of the cemented carbide near the active surface
Elaboration de carbures cĂ©mentĂ©s Ă gradient de propriĂ©tĂ©s par imbibition rĂ©active : Application aux inserts dâoutils tricĂŽne pour le forage pĂ©trolier et minier
Les carbures cĂ©mentĂ©s sont trĂšs utilisĂ©s dans lâindustrie du forage pĂ©trolier et minier, et dans lâusinage en tant que piĂšces rĂ©sistantes Ă lâabrasion et Ă lâimpact. En effet, ces matĂ©riaux possĂšdent un excellent compromis entre duretĂ© et tĂ©nacitĂ©. Cependant, des conditions de plus en plus sĂ©vĂšres, comme le forage profond pour lâindustrie pĂ©troliĂšre et haute tempĂ©rature pour la gĂ©othermie, rendent nĂ©cessaire le dĂ©veloppement de tels matĂ©riaux encore plus performants. Ils doivent ĂȘtre Ă la fois plus tenaces mais Ă©galement rĂ©sister Ă des usures abrasives toujours plus sĂ©vĂšres. Afin dâamĂ©liorer ces deux propriĂ©tĂ©s antagonistes, lâidĂ©e la plus simple est de conserver les mĂȘmes constituants dont les propriĂ©tĂ©s intrinsĂšques restent intĂ©ressantes puis dâintroduire dans ce matĂ©riau un gradient de composition, i.e. un gradient de phase liante. Dans le domaine des carbures cĂ©mentĂ©s, lâintĂ©rĂȘt de ce concept a Ă©tĂ© dĂ©montrĂ© dĂšs les annĂ©es 70, avant mĂȘme le foisonnement dâĂ©tudes dix ans aprĂšs pour les matĂ©riaux FGMs (Functionally Graded Materials) impulsĂ© par le Japon. Depuis, de nombreux travaux ont concernĂ© lâĂ©laboration et la caractĂ©risation de tels matĂ©riaux FGMs qui dĂ©passent largement le cadre des carbures cĂ©mentĂ©s mais sont le plus souvent issus de la famille des cermets et des alliages lourds (Heavy alloys). Toutefois, peu de matĂ©riaux Ă gradient de composition ont Ă©tĂ© industrialisĂ©s. Les principales limitations des premiers procĂ©dĂ©s de gradation des carbures cĂ©mentĂ©s Ă©taient la formation de structures graduelles sur de trop faibles distances (infĂ©rieures au mm), leur mise en Ćuvre dĂ©licate par certaines techniques issues du frittage conventionnel ou encore la formation de dĂ©fauts mĂ©tallurgiques (prĂ©sence de phases η-M6C) compromettant le bĂ©nĂ©fice apportĂ© par la gradation. Les travaux prĂ©sentĂ©s ici concernent le procĂ©dĂ© dâimbibition rĂ©active actuellement dĂ©veloppĂ© par Armines/Centre des MatĂ©riaux Mines-ParisTech et la sociĂ©tĂ© Varel Europe qui est lâun des derniers outilleurs français installĂ© prĂšs de Tarbes. Ce procĂ©dĂ© peut ĂȘtre dĂ©composĂ© en deux procĂ©dĂ©s de gradation, Ă savoir : lâimbibition et le revĂȘtement rĂ©actif. Le rĂŽle de lâimbibition est dâenrichir graduellement en phase liante et en volume le cĆur dâune piĂšce en carbure cĂ©mentĂ© dense. Quant au revĂȘtement rĂ©actif, son rĂŽle est de venir durcir graduellement la surface de ce mĂȘme matĂ©riau Ă lâaide dâune fine prĂ©cipitation de borures ternaires, aux dĂ©pens de la phase liante et des carbures WC, sur Ă©galement des profondeurs millimĂ©triques. Le procĂ©dĂ© dâimbibition rĂ©active dĂ©crit ci-dessus est le seul procĂ©dĂ© de gradation connu Ă ce jour permettant de gĂ©nĂ©rer des gradients continus de plusieurs centaines de HV sur des dizaines de millimĂštres. Dans le cas de piĂšces industrielles (inserts tricĂŽne et taillants PDC (Polycrystalline Diamond Compact)), les gradients de duretĂ© obtenus sont de lâordre de 450 HV sur 25 mm. Ces diffĂ©rentes parties actives des deux principaux outils de forage (tricĂŽne et PDC) ont montrĂ© une hausse trĂšs significative de leurs performances en laboratoire aprĂšs traitement par imbibition rĂ©active. Leurs rĂ©sistances Ă lâabrasion prĂ©sentent une augmentation de lâordre de 30 Ă 100% par rapport Ă des outils non graduĂ©s. De mĂȘme, leurs rĂ©sistances Ă lâimpact sâavĂšrent supĂ©rieures en moyenne Ă 20% mais peuvent ĂȘtre au maximum de 40% pour certaines configurations. Des essais chantiers sont en cours et les premiers rĂ©sultats sont encourageants
Quality and wear behavior of graded polycrystalline diamond compact cutters.
The wear behavior of conventional and graded polycrystalline diamond compact cutters was studied using a vertical lathe with mortar counterfaces. Different cutters were considered regarding to their diamond grain size and the high pressure and the high temperature conditions of the manufacturing process (HPHT). On the base of these cutters, a cobalt graduation process was performed on the WCâCo substrates by reactive imbibition. A quality factor developed in previous studies was calculated to evaluate cutters wear performances. The results showed that a controlled HPHT process can act on the wear resistance certainly by improving the diamond grain boundary cohesion. Unexpectedly, the diamond granulometry appeared to be a secondary factor influencing the wear resistance. The reactive imbibition clearly increased the wear resistance, even for cutters with coarse diamond grains (i.e. potentially impact resistant). Finally, a third body approach describes that the quartz particles detached from the mortar rock realizes abrasive scratches on the cutters wear flat. When the wear flat reaches the substrate, the formation of voids in the contact, associated with the trapping of abrasive particles, rises the wear kinetic. As a secondary mechanism, Raman spectroscopy measurements highlighted tribological transformed structures by the formation of graphite and amorphous carbon on the diamond worn surfaces
A hybrid CMV-H1 construct improves efficiency of PEI-delivered shRNA in the mouse brain
RNA-interference-driven loss of function in specific tissues in vivo should permit analysis of gene function in temporally and spatially defined contexts. However, delivery of efficient short hairpin RNA (shRNA) to target tissues in vivo remains problematic. Here, we demonstrate that efficiency of polyethylenimine (PEI)-delivered shRNA depends on the regulatory sequences used, both in vivo and in vitro. When tested in vivo, silencing of a luciferase target gene by shRNA produced from a hybrid construct composed of the CMV enhancer/promoter placed immediately upstream of an H1 promoter (50%) exceeds that obtained with the H1 promoter alone (20%). In contrast, in NIH 3T3 cells, the H1 promoter was more efficient than the hybrid construct (75 versus 60% inhibition of target gene expression, respectively). To test CMV-H1 shRNA efficiency against an endogenous gene in vivo, we used shRNA against thyroid hormone receptor α1 (TRα1). When vectorized in the mouse brain, the hybrid construct strongly derepressed CyclinD1-luciferase reporter gene expression, CyclinD1 being a negatively regulated thyroid hormone target gene. We conclude that promoter choice affects shRNA efficiency distinctly in different in vitro and in vivo situations and that a hybrid CMV-H1 construct is optimal for shRNA delivery in the mouse brain
Early markers of airways inflammation and occupational asthma: Rationale, study design and follow-up rates among bakery, pastry and hairdressing apprentices
<p>Abstract</p> <p>Background</p> <p>Occupational asthma is a common type of asthma caused by a specific agent in the workplace. The basic alteration of occupational asthma is airways inflammation. Although most patients with occupational asthma are mature adults, there is evidence that airways inflammation starts soon after inception of exposure, including during apprenticeship. Airways hyper responsiveness to methacholine is a valid surrogate marker of airways inflammation, which has proved useful in occupational epidemiology. But it is time-consuming, requires active subject's cooperation and is not readily feasible. Other non-invasive and potentially more useful tests include the forced oscillation technique, measurement of fraction exhaled nitric oxide, and eosinophils count in nasal lavage fluid.</p> <p>Methods and design</p> <p>This study aims to investigate early development of airways inflammation and asthma-like symptoms in apprentice bakers, pastry-makers and hairdressers, three populations at risk of occupational asthma whose work-related exposures involve agents of different nature. The objectives are to (i) examine the performance of the non-invasive tests cited above in detecting early airways inflammation that might eventually develop into occupational asthma; and (ii) evaluate whether, and how, constitutional (e.g. atopy) and behavioural (e.g. smoking) risk factors for occupational asthma modulate the effects of allergenic and/or irritative substances involved in these occupations. This paper presents the study rationale and detailed protocol.</p> <p>Discussion</p> <p>Among 441 volunteers included at the first visit, 354 attended the fourth one. Drop outs were investigated and showed unrelated to the study outcome. Sample size and follow-up participation rates suggest that the data collected in this study will allow it to meet its objectives.</p
Elaboration de carbures cémentés à gradient de propriétés par imbibition réactive : application au forage pétrolier
Les carbures cĂ©mentĂ©s sont trĂšs utilisĂ©s dans lâindustrie du forage pĂ©trolier et minier, et dans lâusinage en tant que piĂšces rĂ©sistantes Ă lâabrasion et Ă lâimpact. En effet, ces matĂ©riaux possĂšdent un excellent compromis entre duretĂ© et tĂ©nacitĂ©. Cependant, des conditions de plus en plus sĂ©vĂšres, comme le forage profond pour lâindustrie pĂ©troliĂšre et haute tempĂ©rature pour la gĂ©othermie, rendent nĂ©cessaire le dĂ©veloppement de tels matĂ©riaux encore plus performants. Ils doivent ĂȘtre Ă la fois plus tenaces mais Ă©galement rĂ©sister Ă des usures abrasives toujours plus sĂ©vĂšres.
Afin dâamĂ©liorer ces deux propriĂ©tĂ©s antagonistes, lâidĂ©e la plus simple est de conserver les mĂȘmes
constituants dont les propriĂ©tĂ©s intrinsĂšques restent intĂ©ressantes puis dâintroduire dans ce matĂ©riau un
gradient de composition, i.e. un gradient de phase liante. Dans le domaine des carbures cémentés,
lâintĂ©rĂȘt de ce concept a Ă©tĂ© dĂ©montrĂ© dĂšs les annĂ©es 70, avant mĂȘme le foisonnement dâĂ©tudes dix ans
aprÚs pour les matériaux FGMs (Functionally Graded Materials) impulsé par le Japon. Depuis, de
nombreux travaux ont concernĂ© lâĂ©laboration et la caractĂ©risation de tels matĂ©riaux FGMs qui dĂ©passent
largement le cadre des carbures cémentés mais sont le plus souvent issus de la famille des cermets et
des alliages lourds (Heavy alloys). Toutefois, peu de matériaux à gradient de composition ont été
industrialisés.
Les principales limitations des premiers procédés de gradation des carbures cémentés étaient la
formation de structures graduelles sur de trop faibles distances (inférieures au mm), leur mise en oeuvre
délicate par certaines techniques issues du frittage conventionnel ou encore la formation de défauts
métallurgiques (présence de phases η-M6C) compromettant le bénéfice apporté par la gradation.
Les travaux prĂ©sentĂ©s ici concernent le procĂ©dĂ© dâimbibition rĂ©active actuellement dĂ©veloppĂ© par
Armines/Centre des MatĂ©riaux Mines-ParisTech et la sociĂ©tĂ© Varel Europe qui est lâun des derniers
outilleurs français installé prÚs de Tarbes.
Ce procĂ©dĂ© peut ĂȘtre dĂ©composĂ© en deux procĂ©dĂ©s de gradation, Ă savoir : lâimbibition et le revĂȘtement
rĂ©actif. Le rĂŽle de lâimbibition est dâenrichir graduellement en phase liante et en volume le coeur dâune piĂšce en carbure cĂ©mentĂ© dense. Quant au revĂȘtement rĂ©actif, son rĂŽle est de venir durcir
graduellement la surface de ce mĂȘme matĂ©riau Ă lâaide dâune fine prĂ©cipitation de borures ternaires, aux
dépens de la phase liante et des carbures WC, sur également des profondeurs millimétriques.
Le procĂ©dĂ© dâimbibition rĂ©active dĂ©crit ci-dessus est le seul procĂ©dĂ© de gradation connu Ă ce jour
permettant de générer des gradients continus de plusieurs centaines de HV sur des dizaines de
millimĂštres. Dans le cas de piĂšces industrielles (inserts tricĂŽne et taillants PDC (Polycrystalline Diamond Compact)), les gradients de duretĂ© obtenus sont de lâordre de 450 HV sur 25 mm.
Ces différentes parties actives des deux principaux outils de forage (tricÎne et PDC) ont montré une
hausse trÚs significative de leurs performances en laboratoire aprÚs traitement par imbibition réactive.
Leurs rĂ©sistances Ă lâabrasion prĂ©sentent une augmentation de lâordre de 30 Ă 100% par rapport Ă des
outils non graduĂ©s. De mĂȘme, leurs rĂ©sistances Ă lâimpact sâavĂšrent supĂ©rieures en moyenne Ă 20%
mais peuvent ĂȘtre au maximum de 40% pour certaines configurations. Des essais chantiers sont en
cours et les premiers résultats sont encourageants
Quantification of short and long asbestos fibers to assess asbestos exposure: a review of fiber size toxicity.
International audienceThe fibrogenicity and carcinogenicity of asbestos fibers are dependent on several fiber parameters including fiber dimensions. Based on the WHO (World Health Organization) definition, the current regulations focalise on long asbestos fibers (LAF) (Length: Lââ„â5Â ÎŒm, Diameter: Dââ3). However air samples contain short asbestos fibers (SAF) (Lâ<â5Â ÎŒm). In a recent study we found that several air samples collected in buildings with asbestos containing materials (ACM) were composed only of SAF, sometimes in a concentration of â„10 fibers.L-1. This exhaustive review focuses on available information from peer-review publications on the size-dependent pathogenetic effects of asbestos fibers reported in experimental in vivo and in vitro studies. In the literature, the findings that SAF are less pathogenic than LAF are based on experiments where a cut-off of 5Â ÎŒm was generally made to differentiate short from long asbestos fibers. Nevertheless, the value of 5Â ÎŒm as the limit for length is not based on scientific evidence, but is a limit for comparative analyses. From this review, it is clear that the pathogenicity of SAF cannot be completely ruled out, especially in high exposure situations. Therefore, the presence of SAF in air samples appears as an indicator of the degradation of ACM and inclusion of their systematic search should be considered in the regulation. Measurement of these fibers in air samples will then make it possible to identify pollution and anticipate health risk
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