3,656 research outputs found
Elementos finitos em formulação mista de mĂnimos quadrados para a simulação da convecção-difusĂŁo em regime transiente
Um esquema de elementos finitos mistos de tipo mĂnimos quadrados Ă© estudado para resolver as equaçÔes da convecção-difusĂŁo transientes expressas em função tanto do campo incĂłgnito primĂĄrio como do seu fluxo, incorporando ou nĂŁo um termo reativo. Uma vez efetuada uma discretização temporal Ă la Crank-Nicholson, o sistema de equaçÔes resultante permite uma aproximação estĂĄvel desses 2 campos, com elementos finitos contĂnuos de Lagrange clĂĄssicos de grau arbitrĂĄrio em geometria de tipo simplex ou nĂŁo, em dimensĂŁo espacial qualquer. O esquema Ă© convergente em espaço no sentido da mĂ©dia quadrĂĄtica no que tange ao campo incĂłgnito primĂĄrio, a seu gradiente, Ă variĂĄvel de fluxo e Ă divergĂȘncia desta Ășltima, e no tempo num sentido apropriado para cada um desses campos. Os resultados numĂ©ricos atestam o bom desempenho do esquema, para quaisquer nĂșmeros de PĂ©clet, confirmando as previsĂ”es teĂłricas, pelo menos no caso de camadas limite estreitas em que o mĂ©todo se mostra fracassado. A tĂ©cnica Ă© tambĂ©m comparada com outros mĂ©todos para resolver essas equaçÔes, incluindo 2 propostos recentemente pelo primeiro autor et al.A mixed least-squares finite element scheme designed for solving the transient convection-diffusion equations expressed in terms of both the primal unknown and its flux, incorporating or not a reaction term, is studied. Once a time discretization of the Crank-Nicholson type is performed, the resulting system of equations allows for a stable approximation of both fields, by means of classical Lagrange continuous piecewise polynomial functions of arbitrary degree, in both simplicial and non-simplicial geometry, in any space dimension. The scheme is also convergent in space in the mean-square sense as far as the primal unknown field, its gradient, the flux variable and its divergence are concerned, and in time in an appropriate sense for each one of these four fields. Numerical results certify that the scheme performs well for any PĂ©clet number, thereby allowing to confirm theoretical predictions, at least in the case where there is no narrow boundary layer. In the latter case however the method fails to produce reliable results. The technique is also compared with three existing methods to solve the convection-diffusion equations in the transient case. These include two recent ones proposed by the first author and collaborators.Peer Reviewe
Anatomia de algumas ocorrĂȘncias de gemas e seu enquadramento em protocolos de ordenamento territorial â contributo para uma reflexĂŁo sobre o estatuto dos depĂłsitos gemĂferos portugueses
[Abstract] Anatomy and Classification of Portuguese Gemstone Deposits and their inclusion in Territorial Management Protocols - The concept of gemstone resources includes the consideration of aspects such as the genetic type of deposits, geographical location and geological characterization of the ores. Based on archeological evidences and assuming the geological potentiality it is possible to consider the existence of resources base with gem quality, in Portugal. The main deposits are related to residual granite systems. In order to ensure a sustainable use, economical or patrimonial, it is necessary to classify these occurrences in a context of land management. This paper presents the typology of the most interesting occurrences considering its economical and patrimonial potentiality
An Investigation of the -type Lorentz-Symmetry Breaking Gauge Models in -Supersymmetric Scenario
In this work, we present two possible venues to accomodate the -type
Lorentz-symmetry violating Electrodynamics in an -supersymmetric
framework. A chiral and a vector superfield are chosen to describe the
background that signals Lorentz-symmetry breaking. In each case, the -tensor is expressed in terms of the components of the
background superfield that we choose to describe the breaking. We also present
in detail the actions with all fermionic partners of the background that
determine .Comment: 10 page
Graft-Copolymerization of Acrylate Monomers onto Chitosan Induced by Gamma Radiation: Amphiphilic Polymers and Their Behavior at The Air-Water Interface
Graft polymerization induced by ionizing radiation is a powerful tool in materials science to modifying the physical properties of polymers. Chitosan is a biocompatible, biodegradable, antibacterial, and highly hydrophilic polysaccharide. In this work, we report the obtaining of amphiphilic polymers through graft polymerization of acrylic monomers (methyl acrylate, t-butyl acrylate, and hexyl acrylate) onto chitosan. The polymerization reaction was carried out by simultaneous irradiation of monomers and chitosan using a gamma radiation source of 60Co. The formation of Langmuir films of amphiphilic polymers was studied at the air-water interface through surface pressure versus main molecular area isotherms (Î -A) and hysteresis cycles of compression and decompression. Finally, it was analyzed the transferring of Langmuir films towards solid substrates to obtaining Langmuir-Blodgett films with potential application as an antibacterial coating. The microstructure of the Langmuir-Blodgett films was characterized by AFM microscopy observing a regular topography with roughness ranging between 0.53 and 0.6 ÎŒm
Invariants from classical field theory
We introduce a method that generates invariant functions from perturbative
classical field theories depending on external parameters. Applying our methods
to several field theories such as abelian BF, Chern-Simons and 2-dimensional
Yang-Mills theory, we obtain, respectively, the linking number for embedded
submanifolds in compact varieties, the Gauss' and the second Milnor's invariant
for links in S^3, and invariants under area-preserving diffeomorphisms for
configurations of immersed planar curves.Comment: 20 pages, 1 figure, to appear in J. Math. Phy
Thermochromic Paints on External Surfaces: Impact Assessment for a Residential Building through Thermal and Energy Simulation
This work addresses the effect of using thermochromic paints in residential buildings. Two different thermochromic paint types were considered: One that changes properties through a step transition at a certain temperature, and another that changes properties in a gradual/linear manner throughout a temperature range. The studied building was a two-floor villa, virtually simulated through a digital model with and without thermal insulation, and considering thermochromic paints applied both on external walls and on the roof. The performance assessment was done through the energy use for heating and cooling (in conditioned mode), as well as in terms of the indoor temperature (in free-floating mode). Three different cities/climates were considered: Porto, Madrid, and Abu Dhabi. Results showed that energy savings up to 50.6% could be reached if the building is operated in conditioned mode. Conversely, when operated in free-floating mode, optimally selected thermochromic paints enable reductions up to 11.0 degrees C, during summertime, and an increase up to 2.7 degrees C, during wintertime. These results point out the great benefits of using optimally selected thermochromic paints for obtaining thermal comfort, and also the need to further develop stable and cost-effective thermochromic pigments for outdoor applications, as well as to test physical models in a real environment
Superpulsed low-level laser therapy protects skeletal muscle of mdx mice against damage, inflammation and morphological changes delaying dystrophy progression.
Aim: To evaluate the effects of preventive treatment with low-level laser therapy (LLLT) on progression of dystrophy in mdx mice. Methods: Ten animals were randomly divided into 2 experimental groups treated with superpulsed LLLT (904 nm, 15 mW, 700 Hz, 1 J) or placebo-LLLT at one point overlying the tibialis anterior muscle (bilaterally) 5 times per week for 14 weeks (from 6th to 20th week of age). Morphological changes, creatine kinase (CK) activity and mRNA gene expression were assessed in animals at 20th week of age. Results: Animals treated with LLLT showed very few morphological changes in skeletal muscle, with less atrophy and fibrosis than animals treated with placebo-LLLT. CK was significantly lower (p = 0.0203) in animals treated with LLLT (864.70 U.lâ1, SEM 226.10) than placebo (1708.00 U.lâ1, SEM 184.60). mRNA gene expression of inflammatory markers was significantly decreased by treatment with LLLT (p<0.05): TNF-α (placebo-control = 0.51 ”g/”l [SEM 0.12], - LLLT = 0.048 ”g/”l [SEM 0.01]), IL-1ÎČ (placebo-control = 2.292 ”g/”l [SEM 0.74], - LLLT = 0.12 ”g/”l [SEM 0.03]), IL-6 (placebo-control = 3.946 ”g/”l [SEM 0.98], - LLLT = 0.854 ”g/”l [SEM 0.33]), IL-10 (placebo-control = 1.116 ”g/”l [SEM 0.22], - LLLT = 0.352 ”g/”l [SEM 0.15]), and COX-2 (placebo-control = 4.984 ”g/”l [SEM 1.18], LLLT = 1.470 ”g/”l [SEM 0.73]). Conclusion: Irradiation of superpulsed LLLT on successive days five times per week for 14 weeks decreased morphological changes, skeletal muscle damage and inflammation in mdx mice. This indicates that LLLT has potential to decrease progression of Duchenne muscular dystrophy
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