310 research outputs found
Absorption rapide de liquide dans un réseau capillaire uniforme
Affiche prĂ©sentĂ©e dans le cadre du Colloque de l'ARC, «Des racines et des ailes pour la recherche collĂ©giale», dans le cadre du 85e CongrĂšs de lâAcfas, UniversitĂ© McGill, MontrĂ©al, les 8 et 9 mai 2017.Le phĂ©nomĂšne dâabsorption dâun liquide par un milieu poreux est omniprĂ©sent dans notre environnement, avec des applications aussi variĂ©es que la cuisson des pĂątes, des tests mĂ©dicaux rapides, la purification de lâeauâŠ. Ce phĂ©nomĂšne est particuliĂšrement important pour le futur de lâindustrie papetiĂšre. En effet, bien que la demande pour les papiers destinĂ©s Ă lâimpression soit en baisse, les secteurs de lâemballage et des papiers sanitaires (couches, mouchoirs âŠ) demeure actif. De plus, le dĂ©veloppement de types de papiers bioactifs pouvant dĂ©tecter ou dĂ©truire des agents pathogĂšnes offre de nouveaux dĂ©bouchĂ©s Ă lâindustrie. Le contrĂŽle de lâabsorption de liquide par la structure du papier est crucial au bon fonctionnement de tous ces papiers et cartons. Elle doit ĂȘtre favorisĂ©e pour les papiers sanitaires, mais rĂ©duite au strict minimum dans les emballages alimentaires. La pĂ©nĂ©tration dâun fluide dans un papier demeure cependant un phĂ©nomĂšne mĂ©connu, et cette connaissance repose de plus sur un ensemble de notions empiriques souvent adaptĂ©es Ă des cas trĂšs prĂ©cis seulement. Nos travaux cherchent Ă comprendre en dĂ©tail lâinfluence de la structure des pores sur le dĂ©bit dâabsorption des liquides. Un ensemble de simulations numĂ©riques et de calculs analytiques basĂ©s sur les Ă©quations de la mĂ©canique des fluides nous a dĂ©montrĂ© quâune structure prĂ©sentant de longs pores dans lâaxe dâabsorption du liquide optimise le dĂ©bit, dont la limite est dĂ©terminĂ©e par la taille des pores
Fluctuations in fluid invasion into disordered media
Interfaces moving in a disordered medium exhibit stochastic velocity
fluctuations obeying universal scaling relations related to the presence or
absence of conservation laws. For fluid invasion of porous media, we show that
the fluctuations of the velocity are governed by a geometry-dependent length
scale arising from fluid conservation. This result is compared to the
statistics resulting from a non-equilibrium (depinning) transition between a
moving interface and a stationary, pinned one.Comment: 4 pages, 4 figure
Rimouski : population et Ă©conomie
Les progrĂšs de 1'urbanisme dans notre milieu sâaccompagnent dâune multiplication des monographies urbaines, 1'urbaniste devant appuyer ses propositions sur une connaissance aussi exacte que possible des territoires dont il a Ă orienter 1' expansion. De telles monographies rassemblent souvent des matĂ©riaux qu'ont tout intĂ©rĂȘt Ă relever ceux qui se prĂ©occupent de l'Ă©laboration d'une sociographie du QuĂ©bec. C'est le cas de l'Ă©tude prĂ©parĂ©e par Yves DubĂ© et Yves Martin Ăą la demande des urbanistes chargĂ©s de mettre au point le "plan directeur" de 1'agglomĂ©ration de Rimouski; les auteurs exposent ici l'essentiel de leurs analyses consacrĂ©es Ăą la population et Ă 1'Ă©conomie de cette agglomĂ©ration
Decoherence in a N-qubit solid-state quantum computer
We investigate the decoherence process for a quantum register composed of N
qubits coupled to an environment. We consider an environment composed of one
common phonon bath and several electronic baths. This environment is relevant
to the implementation of a charge based solid-state quantum computer. We
explicitly compute the time evolution of all off-diagonal terms of the
register's reduced density matrix. We find that in realistic configurations,
"superdecoherence" and "decoherence free subspaces" do not exist for an N-qubit
system. This means that all off-diagonal terms decay like exp(-q(t)N), where
q(t) is of the same order as the decay function of a single qubit.Comment: 11 page
Droplet spreading and pinning on heterogeneous substrates
The contact angle of a fluid droplet on an heterogeneous surface is analysed
using the statistical dynamics of the spreading contact line. The statistical
properties of the final droplet radius and contact angle are obtained through
applications of depinning transitions of contact lines with non-local
elasticity and features of pinning-depinning dynamics. Such properties not only
depend on disorder strength and surface details, but also on the droplet volume
and disorder correlation length. Deviations from Wenzel or Cassie/Baxter
behaviour are particularly apparent in the case of small droplet volumes and
small contact angles.Comment: accepted to Phys. Rev. E, 5 figure
Material selection methodology for an induction welding magnetic susceptor based on hysteresis losses
ABSTRACT: Induction welding is a fusion bonding process relying on the application of an alternating magnetic field to generate heat at the joining interface. Herein, magnetic hysteresis losses heating elements, called susceptors, which are made of magnetic particles dispersed in a thermoplastic polymer, are investigated. A methodology to identify the parameters influencing the heating rate of the susceptors and to select suitable magnetic particles for their fabrication is proposed. The applied magnetic field amplitude is modeled based on the induction coil geometry and the alternating electrical current introduced to it. Then, properties of the evaluated susceptor particles are obtained through measurements of their magnetic hysteresis. A case study is presented to validate the suitability of the proposed methodology. Particles of iron (Fe), nickel (Ni), and magnetite (FeâOâ) are evaluated as susceptor materials in polypropylene (PP) and polyetheretherketone (PEEK) matrices. Heating rates are predicted using the proposed method, and samples are produced and heated by induction to experimentally verify the results. Good agreement with the predictions is obtained. Ni is the most suitable susceptor material for a PP matrix, while FeâOâ is preferable for PEEK
Epileptogenesis after prolonged febrile seizures: mechanisms, biomarkers and therapeutic opportunities.
Epidemiological and recent prospective analyses of long febrile seizures (FS) and febrile status epilepticus (FSE) support the idea that in some children, such seizures can provoke temporal lobe epilepsy (TLE). Because of the high prevalence of these seizures, if epilepsy was to arise as their direct consequence, this would constitute a significant clinical problem. Here we discuss these issues, and describe the use of animal models of prolonged FS and of FSE to address the following questions: Are long FS epileptogenic? What governs this epileptogenesis? What are the mechanisms? Are there any predictive biomarkers of the epileptogenic process, and can these be utilized, together with information about the mechanisms of epileptogenesis, for eventual prevention of the TLE that results from long FS and FSE
Thermal effects on atomic friction
We model friction acting on the tip of an atomic force microscope as it is
dragged across a surface at non-zero temperatures. We find that stick-slip
motion occurs and that the average frictional force follows ,
where is the tip velocity. This compares well to recent experimental work
(Gnecco et al, PRL 84, 1172), permitting the quantitative extraction of all
microscopic parameters. We calculate the scaled form of the average frictional
force's dependence on both temperature and tip speed as well as the form of the
friction-force distribution function.Comment: Accepted for publication, Physical Review Letter
Cap sur la prĂ©vention: Vers le dĂ©veloppement d'une culture de sĂ©curitĂ© dans l'industrie de la capture des pĂȘches maritimes commerciales
Le prĂ©sent projet de recherche est une initiative du ComitĂ© permanent sur la sĂ©curitĂ© des bateaux de pĂȘche du QuĂ©bec (CPSBPQ), qui est un organisme Ă but non lucratif vouĂ© Ă la promotion et au dĂ©veloppement dâune saine culture de santĂ© et sĂ©curitĂ© dans lâindustrie de la capture des pĂȘches maritimes commerciales. Cette recherche a Ă©tĂ© rendue possible grĂące notamment Ă la prĂ©cieuse collaboration et au soutien de la SĂ©curitĂ© et sĂ»retĂ© maritime de Transports Canada, rĂ©gion du
Québec, principal partenaire dans le projet.
Le RĂ©seau QuĂ©bec Maritime (RQM), fortement intĂ©ressĂ© par lâapproche innovante et intersectorielle du CPSBPQ en
matiĂšre de dĂ©veloppement de la culture de sĂ©curitĂ© dans les pĂȘches, a acceptĂ© la prĂ©sente recherche comme projet levier de sa thĂ©matique «Surveillance, sĂ»retĂ© et sĂ©curitĂ© maritime».
Les divers partenaires des gouvernements provincial et fĂ©dĂ©ral actifs au sein du CPSBPQ, dĂ©sireux Ă©galement de voir une amĂ©lioration dans la sĂ©curitĂ© des pĂȘches, ont rĂ©pondu favorablement Ă lâappel. Ainsi la Garde cĂŽtiĂšre canadienne (GCC), PĂȘches et OcĂ©ans Canada (MPO) et la Commission des normes, de lâĂ©quitĂ©, de la santĂ© et de la sĂ©curitĂ© du travail (CNESST) se sont impliquĂ©s dans cette recherche dâenvergure.
Le CPSBPQ, Ă©paulĂ© par le personnel du Bureau de premiĂšre responsabilitĂ© â PĂȘche de la SĂ©curitĂ© et sĂ»retĂ© maritime de Transports Canada Ă Rimouski, sâest Ă©galement associĂ© Ă deux chercheurs de lâUniversitĂ© de Sherbrooke ainsi quâĂ un chercheur de lâInstitut de recherche Robert-SauvĂ© en santĂ© et en sĂ©curitĂ© du travail (IRSST), pour mener Ă bien ce projet
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