1,493 research outputs found
Interaction of point sources and vortices for incompressible planar fluids
We consider a new system of differential equations which is at the same time
gradient and locally Hamiltonian. It is obtained by just replacing a factor in
the equations of interaction for N point vortices, and it is interpreted as an
interaction of N point sources. Because of the local Hamiltonian structure and
the symmetries it obeys, it does possess some of the first integrals that
appear in the N vortex problem. We will show that binary collisions are easily
blown up in this case since the equations of motion are of first order. This
method may be easily generalized to the blow up of higher order collisions. We
then generalize the model further to interactions of sources and vortices.Comment: 9 page
Volcanic Scoria as Cement Replacement
Numerous volcanic scoria (VS) cones are found in many places of the world. Many of them have not yet been investigated, although few have been used as binders for a very long time. The use of natural pozzolans as cement replacement could be considered as a common practice in the construction industry due to the related economic, ecologic and performance benefits. This chapter highlights the advantages and disadvantages of the use of volcanic scoria as cement replacement in concrete mixes in terms of fresh and hardened concrete properties. The chemical and mineralogical composition of volcanic scoria samples collected from 36 countries is presented in this chapter, with some further analysis. The effects of using volcanic scoria as cement replacement on some paste, mortar and concrete properties, such as the setting times, the heat of hydration, the compressive strength, the water permeability and the chloride penetrability, have been studied. The improvement in resistance against the chemical attack of volcanic scoria-based cement mortar has also been highlighted. Some estimation equations depending on the data available in literature have also been derived from the analyzed data. The modification of the microstructure of VS-based cement paste has been confirmed, as well
Reconfigurable elastic neuromorphic metasurfaces towards mechanical intelligence and cognitive wave-based computing
The ability of mechanical systems to perform basic computations has gained
traction over recent years, providing an unconventional alternative to digital
computing in off grid, low power, and severe thermal environments which render
the majority of electronic components inoperable. However, much of the work in
mechanical computing has focused on logic operations via quasi-static
prescribed displacements in origami, bistable, and soft deformable matter. In
here, we present a first attempt to describe the fundamental framework of an
elastic neuromorphic metasurface that performs distinct classification tasks,
providing a new set of challenges given the complex nature of elastic waves
with respect to scattering and manipulation. Multiple layers of reconfigurable
waveguides are phase-trained via constant weights and trainable activation
functions in a manner that enables the resultant wave scattering at the readout
location to focus on the correct class within the detection plane. We
demonstrate the neuromorphic system's ability to exhibit high accuracy in two
distinct tasks owing to a fully reconfigurable design, eliminating the need for
costly remanufacturing
Role perceptions and role performance of instructional supervisors as perceived by teachers and supervisors in the public schools of Qatar.
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