1,698 research outputs found
Dynamics and interactions of active rotors
We consider a simple model of an internally driven self-rotating object; a
rotor, confined to two dimensions by a thin film of low Reynolds number fluid.
We undertake a detailed study of the hydrodynamic interactions between a pair
of rotors and find that their effect on the resulting dynamics is a combination
of fast and slow motions. We analyse the slow dynamics using an averaging
procedure to take account of the fast degrees of freedom. Analytical results
are compared with numerical simulations. Hydrodynamic interactions mean that
while isolated rotors do not translate, bringing together a pair of rotors
leads to motion of their centres. Two rotors spinning in the same sense rotate
with an approximately constant angular velocity around each other, while two
rotors of opposite sense, both translate with the same constant velocity, which
depends on the separation of the pair. As a result a pair of counter-rotating
rotors are a promising model for controlled self-propulsion.Comment: 6 pages, 6 figure
Violation and persistence of the K-quantum number in warm rotating nuclei
The validity of the K-quantum number in rapidly rotating warm nuclei is
investigated as a function of thermal excitation energy U and angular momentum
I, for the rare-earth nucleus 163Er. The quantal eigenstates are described with
a shell model which combines a cranked Nilsson mean-field and a residual
two-body interaction, together with a term which takes into account the angular
momentum carried by the K-quantum number in an approximate way. K-mixing is
produced by the interplay of the Coriolis interaction and the residual
interaction; it is weak in the region of the discrete rotational bands (U
\lesim 1MeV), but it gradually increases until the limit of complete violation
of the K-quantum number is approached around U \sim 2 - 2.5 MeV. The calculated
matrix elements between bands having different K-quantum numbers decrease
exponentially as a function of , in qualitative agreement with recent
data.Comment: 29 pages, 7 figure
Effect of Supplementary Irrigation on Yield of Chickpea Genotypes in a Mediterranean Climate
Rosana G. Moreira, Editor-in-Chief; Texas A&M UniversityThis is a paper from International Commission of Agricultural Engineering (CIGR, Commission Internationale du Genie Rural) E-Journal Volume 8 (2006): Effect of Supplementary Irrigation on Yield of Chickpea Genotypes in a Mediterranean Climate. Manuscript LW 04 005. Vol. VIII. May, 2006
Swimmers in thin films: from swarming to hydrodynamic instabilities
We investigate theoretically the collective dynamics of a suspension of low
Reynolds number swimmers that are confined to two dimensions by a thin fluid
film. Our model swimmer is characterized by internal degrees of freedom which
locally exert active stresses (force dipoles or quadrupoles) on the fluid. We
find that hydrodynamic interactions mediated by the film can give rise to
spontaneous continuous symmetry breaking (swarming), to states with either
polar or nematic homogeneous order. For dipolar swimmers, the stroke averaged
dynamics are enough to determine the leading contributions to the collective
behaviour. In contrast, for quadrupolar swimmers, our analysis shows that
detailed features of the internal dynamics play an important role in
determining the bulk behaviour. In the broken symmetry phases, we investigate
fluctuations of hydrodynamic variables of the system and find that these
destabilize order. Interestingly, this instability is not generic and depends
on length-scale.Comment: 4 pages, 2 figures, references added, typos corrected, new
introductio
The first solvent-free cyclotrimerization reaction of arylethynes catalyzed by rhodium porphyrins
Different rhodium(III) porphyrin chlorides have been used as catalysts for the cyclotrimerization of several arylethynes, giving in many cases high yields in substituted benzenes and selectivities based on the steric hindrance of the macrocycles and on the substitution of the substrates
Avaliação do efeito cicatrizante da quitosana por aplicação tópica em ratos.
bitstream/CNPDIA-2009-09/11045/1/DOC29_2007.pd
Adaptive Process Management in Highly Dynamic and Pervasive Scenarios
Process Management Systems (PMSs) are currently more and more used as a
supporting tool for cooperative processes in pervasive and highly dynamic
situations, such as emergency situations, pervasive healthcare or domotics/home
automation. But in all such situations, designed processes can be easily
invalidated since the execution environment may change continuously due to
frequent unforeseeable events. This paper aims at illustrating the theoretical
framework and the concrete implementation of SmartPM, a PMS that features a set
of sound and complete techniques to automatically cope with unplanned
exceptions. PMS SmartPM is based on a general framework which adopts the
Situation Calculus and Indigolog
Measuring close proximity interactions in summer camps during the COVID-19 pandemic
Policy makers have implemented multiple non-pharmaceutical strategies to mitigate the COVID-19 worldwide crisis. Interventions had the aim of reducing close proximity interactions, which drive the spread of the disease. A deeper knowledge of human physical interactions has revealed necessary, especially in all settings involving children, whose education and gathering activities should be preserved. Despite their relevance, almost no data are available on close proximity contacts among children in schools or other educational settings during the pandemic. Contact data are usually gathered via Bluetooth, which nonetheless offers a low temporal and spatial resolution. Recently, ultra-wideband (UWB) radios emerged as a more accurate alternative that nonetheless exhibits a significantly higher energy consumption, limiting in-field studies. In this paper, we leverage a novel approach, embodied by the Janus system that combines these radios by exploiting their complementary benefits. The very accurate proximity data gathered in-field by Janus, once augmented with several metadata, unlocks unprecedented levels of information, enabling the development of novel multi-level risk analyses. By means of this technology, we have collected real contact data of children and educators in three summer camps during summer 2020 in the province of Trento, Italy. The wide variety of performed daily activities induced multiple individual behaviors, allowing a rich investigation of social environments from the contagion risk perspective. We consider risk based on duration and proximity of contacts and classify interactions according to different risk levels. We can then evaluate the summer camps’ organization, observe the effect of partition in small groups, or social bubbles, and identify the organized activities that mitigate the riskier behaviors. Overall, we offer an insight into the educator-child and child-child social interactions during the pandemic, thus providing a valuable tool for schools, summer camps, and policy makers to (re)structure educational activities safely
GDR Feeding of the Highly-Deformed Band in 42Ca
The gamma-ray spectra from the decay of the GDR in the compound nucleus
reaction 18O+28Si at bombarding energy of 105 MeV have been measured in an
experiment using the EUROBALL IV and HECTOR arrays. The obtained experimental
GDR strength function is highly fragmented, with a low energy (10 MeV)
component, indicating a presence of a large deformation and Coriolis effects.
In addition, the preferential feeding of the highly-deformed band in 42Ca by
this GDR low energy component is observed.Comment: 6 pages, 2 figures, Proceedings of the Zakopane2004 Symposium, to be
published in Acta Phys. Pol. B36 (2005
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