321 research outputs found
Damping of liquid sloshing by foams
When a container is set in motion, the free surface of the liquid starts to
oscillate or slosh. Such effects can be observed when a glass of water is
handled carelessly and the fluid sloshes or even spills over the rims of the
container. However, beer does not slosh as readily as water, which suggests
that foam could be used to damp sloshing. In this work, we study experimentally
the effect on sloshing of a liquid foam placed on top of a liquid bath. We
generate a monodisperse two-dimensional liquid foam in a rectangular container
and track the motion of the foam. The influence of the foam on the sloshing
dynamics is experimentally characterized: only a few layers of bubbles are
sufficient to significantly damp the oscillations. We rationalize our
experimental findings with a model that describes the foam contribution to the
damping coefficient through viscous dissipation on the walls of the container.
Then we extend our study to confined three-dimensional liquid foam and observe
that the behavior of 2D and confined 3D systems are very similar. Thus we
conclude that only the bubbles close to the walls have a significant impact on
the dissipation of energy. The possibility to damp liquid sloshing using foam
is promising in numerous industrial applications such as the transport of
liquefied gas in tankers or for propellants in rocket engines.Comment: 17 pages, accepted in Physics of Fluid
Les enjeux associés à l'appropriation de ressources numériques muséales par des enseignants du secondaire du Québec : proposition d'un cadre d'analyse
Depuis 2014, le Musée des beaux-arts de Montréal développe une plateforme nommée ÉducArt, qui suggère des activités éducatives réalisées à partir de sa collection encyclopédique pour soutenir les écoles secondaires québécoises dans leur mission culturelle. Comme l’élaboration de ressources destinées au milieu scolaire demande de tenir compte des besoins et des réalités de la classe (Van der Maren, 1996, 2003) et que le gouvernement du Québec entend poursuivre le financement de plateformes muséales (Rocheleau, 2016), il apparaît important d’étudier les enjeux associés à l’appropriation de ressources numériques muséales, telles que celles diffusées sur la plateforme ÉducArt, par des enseignants du secondaire du Québec. Dans cette perspective, un cadre d’analyse visant à mieux comprendre ces enjeux semble essentiel. Cet article se veut une contribution en ce sens, car à notre connaissance, aucun modèle théorique n’existe pour comprendre les enjeux particuliers que rencontrent des enseignants du secondaire lorsqu’ils tentent de s’approprier des ressources numériques muséales.Since 2014, the Montreal Museum of Fine Arts develops a platform called ÉducArt, which offers educational activities carried out from its encyclopaedic collection to support Quebec high schools in their cultural mission. As the development of such resources for schools requires consideration of the class needs and realities (Van der Maren, 1996; 2003) and Quebec’s government intends to continue financing museum platforms (Rocheleau, 2016), it appears important to study the issues associated with the appropriation of digital museum resources, such as those published on the ÉducArt platform, by high school teachers in Quebec. In this context, an analytical framework to better understand these issues seems essential. This article is intended to be a contribution in this direction because, to our knowledge, no theoretical model exists in order to specifically understand the issues encountered by high school teachers when trying to appropriate digital museum resources
Overcoming the barriers to implementing urban road user charging schemes
Urban road user charging offers the potential to achieve significant improvements in urban transport, but is notoriously difficult to implement. Cities need guidance on the range of factors to be considered in planning and implementing such schemes. This paper summarises the results of a 3 year programme which has collated evidence on the issues of most concern to cities. A state of the art report has provided evidence on 14 themes, ranging from objectives and design to implementation and evaluation. A set of 16 case studies has reviewed experience in design and implementation across Europe. The paper summarises their findings, provides references to more detailed information, presents the resulting policy recommendations to European, national and local government, and outlines the areas in which further research is needed
2022 Top Trends in Academic Libraries
This article summarizes trending topics in academic librarianship from the past two years–a time of tremendous upheaval and change, including a global pandemic, difficult reflections concerning racial justice, and war between nation states. Rapid changes and uncertainty from these events have created a significant amount of shifts to academic libraries, higher education, and society in general. Such shifts have yielded new perspectives and innovations in how librarians approach delivering services, supporting student success, managing staff and physical spaces, embracing new technology, and managing data. This report attempts to provide a snapshot of developments worth noting
Why do we need a theory and metrics of technology upgrading?
This paper discusses why we need theory and metrics of technology upgrading. It critically reviews the existing approaches to technology upgrading and motivates build-up of theoretically relevant but empirically grounded middle level conceptual and statistical framework which could illuminate a type of challenges relevant for economies at different income levels. It conceptualizes technology upgrading as three dimensional processes composed of intensity and different types of technology upgrading through various types of innovation and technology activities; broadening of technology upgrading through different forms of technology and knowledge diversification, and interaction with global economy through knowledge import, adoption and exchange. We consider this to be necessary first step towards theory and metrics of technology upgrading and generation of more relevant composite indicator of technology upgrading
The influence of skeletal muscle anisotropy on electroporation: in vivo study and numerical modeling
The aim of this study was to theoretically and experimentally investigate electroporation of mouse tibialis cranialis and to determine the reversible electroporation threshold values needed for parallel and perpendicular orientation of the applied electric field with respect to the muscle fibers. Our study was based on local electric field calculated with three-dimensional realistic numerical models, that we built, and in vivo visualization of electroporated muscle tissue. We established that electroporation of muscle cells in tissue depends on the orientation of the applied electric field; the local electric field threshold values were determined (pulse parameters: 8 × 100 μs, 1 Hz) to be 80 V/cm and 200 V/cm for parallel and perpendicular orientation, respectively. Our results could be useful electric field parameters in the control of skeletal muscle electroporation, which can be used in treatment planning of electroporation based therapies such as gene therapy, genetic vaccination, and electrochemotherapy
Reduced basis approximation and a posteriori error estimation for the time-dependent viscous Burgers’ equation
In this paper we present rigorous a posteriori L 2 error bounds for reduced basis approximations of the unsteady viscous Burgers’ equation in one space dimension. The a posteriori error estimator, derived from standard analysis of the error-residual equation, comprises two key ingredients—both of which admit efficient Offline-Online treatment: the first is a sum over timesteps of the square of the dual norm of the residual; the second is an accurate upper bound (computed by the Successive Constraint Method) for the exponential-in-time stability factor. These error bounds serve both Offline for construction of the reduced basis space by a new POD-Greedy procedure and Online for verification of fidelity. The a posteriori error bounds are practicable for final times (measured in convective units) T≈O(1) and Reynolds numbers ν[superscript −1]≫1; we present numerical results for a (stationary) steepening front for T=2 and 1≤ν[superscript −1]≤200.United States. Air Force Office of Scientific Research (AFOSR Grant FA9550-05-1-0114)United States. Air Force Office of Scientific Research (AFOSR Grant FA-9550-07-1-0425)Singapore-MIT Alliance for Research and Technolog
Expression of Distal-less, dachshund, and optomotor blind in Neanthes arenaceodentata (Annelida, Nereididae) does not support homology of appendage-forming mechanisms across the Bilateria
The similarity in the genetic regulation of
arthropod and vertebrate appendage formation has been
interpreted as the product of a plesiomorphic gene
network that was primitively involved in bilaterian
appendage development and co-opted to build appendages
(in modern phyla) that are not historically related
as structures. Data from lophotrochozoans are needed to
clarify the pervasiveness of plesiomorphic appendage forming
mechanisms. We assayed the expression of three
arthropod and vertebrate limb gene orthologs, Distal-less
(Dll), dachshund (dac), and optomotor blind (omb), in
direct-developing juveniles of the polychaete Neanthes
arenaceodentata. Parapodial Dll expression marks premorphogenetic
notopodia and neuropodia, becoming restricted
to the bases of notopodial cirri and to ventral
portions of neuropodia. In outgrowing cephalic appendages,
Dll activity is primarily restricted to proximal
domains. Dll expression is also prominent in the brain. dac
expression occurs in the brain, nerve cord ganglia, a pair
of pharyngeal ganglia, presumed interneurons linking a
pair of segmental nerves, and in newly differentiating
mesoderm. Domains of omb expression include the brain,
nerve cord ganglia, one pair of anterior cirri, presumed
precursors of dorsal musculature, and the same pharyngeal
ganglia and presumed interneurons that express dac.
Contrary to their roles in outgrowing arthropod and
vertebrate appendages, Dll, dac, and omb lack comparable
expression in Neanthes appendages, implying independent
evolution of annelid appendage development. We infer
that parapodia and arthropodia are not structurally or
mechanistically homologous (but their primordia might
be), that Dll’s ancestral bilaterian function was in sensory
and central nervous system differentiation, and that
locomotory appendages possibly evolved from sensory
outgrowths
Perception of limb orientation in the vertical plane depends on center of mass rather than inertial eigenvectors
We performed two experiments to test the hypothesis that the perception of limb orientation depends on inertial eigenvectors (
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