519 research outputs found
On the Expressiveness of Markovian Process Calculi with Durational and Durationless Actions
Several Markovian process calculi have been proposed in the literature, which
differ from each other for various aspects. With regard to the action
representation, we distinguish between integrated-time Markovian process
calculi, in which every action has an exponentially distributed duration
associated with it, and orthogonal-time Markovian process calculi, in which
action execution is separated from time passing. Similar to deterministically
timed process calculi, we show that these two options are not irreconcilable by
exhibiting three mappings from an integrated-time Markovian process calculus to
an orthogonal-time Markovian process calculus that preserve the behavioral
equivalence of process terms under different interpretations of action
execution: eagerness, laziness, and maximal progress. The mappings are limited
to classes of process terms of the integrated-time Markovian process calculus
with restrictions on parallel composition and do not involve the full
capability of the orthogonal-time Markovian process calculus of expressing
nondeterministic choices, thus elucidating the only two important differences
between the two calculi: their synchronization disciplines and their ways of
solving choices
Biomechanics of the pelvic floor during vaginal delivery
Tese de doutoramento. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto, Instituto Superior Técnico. Universidade de Lisboa, Faculdade de Medicina. Universidade do Porto. 200
Interazioni tra fumi e sistemi sprinkler: analisi fluidodinamica durante un incendio
Gli incendi in galleria costituiscono uno degli scenari incidentali di maggior rischio e sono stati oggetto di ampi studi in letteratura, volti ad indagarne lo sviluppo o l’influenza di vari parametri, come ad esempio l’effetto delle ostruzioni sulla velocità critica di ventilazione. Uno sviluppo minore è invece riscontrabile per quanto riguarda l’utilizzo e gli effetti di impianti di tipo sprinkler per migliorare la sicurezza dei tunnel stradali. Un esempio recente è costituito dallo studio di Zheng e Ingason, in cui l’impiego di sprinkler è stato testato su una riproduzione in scala di una galleria stradale.
Questo studio si propone di indagare l’interazione tra i fumi e i sistemi antincendio fissi ad acqua in galleria, problema che risulta essere tuttora non completamente risolto
Fibre Reinforcement in Living Cells: A Preliminary Study of the F-actin Filaments
AbstractCells are continuously exposed to physical stresses and strains from the Extracellular Matrix (ECM), thus, refining through numer- ical simulations the in vitro conditions during the cultures, may likely promote adequate tissue growth and remodelling [1].This paper describes a simplified three-dimensional constitutive model of the mechanical behaviour of the living cells. The necessary continuum mechanics background is skipped, along with derivations of the stress and spatial elasticity tensors for a transversely isotropic and hyperelastic material. The particular form of the strain energy proposed by Weiss [2] is used to describe the family of fibers. Also, the implementation of hyperelastic materials resorting the commercial finite-element-software Abaqus is discussed.Numerical examples are presented that demonstrate the utility and effectiveness of this approach. More specifically, homoge- neous deformations are imposed and the results compared with the analytical solution. Also, the convergence rate is checked for each case. Following, the use of UMAT routines using jacobian material matrices based on the Jaumann rate of Kirchhoff stress tensor ensured quadratic convergence rates
Advanced turbulence models and boundary conditions for flows around different configurations of ground-mounted buildings
When dealing with Atmospheric Boundary Layer (ABL) simulations, commercial computational fluid dynamics (CFD) acquires a strategic resonance. Thanks to its good compromise between accuracy of results and calculation time, RANS still represents a valid alternative to more resource-demanding methods. However, focusing on the models’ performances in urban studies, LES generally outmatches RANS results, even if the former is at least one order of magnitude more expensive. Consequently, the present work aims to propose a variety of approaches meant to solve some of the major problems linked to RANS simulations and to further improve its accuracy in typical urban contexts. All of these models are capable of switching from an undisturbed flux formulation to a disturbed one through a local deviation or a marker function. For undisturbed flows, a comprehensive approach is adopted, solving the issue of the erroneous stream-wise gradients affecting the turbulent profiles. Around obstacles, Non-Linear Eddy-Viscosity closures are adopted, due to their prominent capability in capturing the anisotropy of turbulence. The purpose of this work is then to propose a new Building Influence Area concept and to offer more affordable alternatives to LES simulations without sacrificing a good grade of accuracy
On the Nonlinear Shaping Gain with Probabilistic Shaping and Carrier Phase Recovery
The performance of different probabilistic amplitude shaping (PAS) techniques
in the nonlinear regime is investigated, highlighting its dependence on the PAS
block length and the interaction with carrier phase recovery (CPR). Different
PAS implementations are considered, based on different distribution matching
(DM) techniques-namely, sphere shaping, shell mapping with different number of
shells, and constant composition DM-and amplitude-to-symbol maps. When CPR is
not included, PAS with optimal block length provides a nonlinear shaping gain
with respect to a linearly optimized PAS (with infinite block length); among
the considered DM techniques, the largest gain is obtained with sphere shaping.
On the other hand, the nonlinear shaping gain becomes smaller, or completely
vanishes, when CPR is included, meaning that in this case all the considered
implementations achieve a similar performance for a sufficiently long block
length. Similar results are obtained in different link configurations (1x180km,
15x80km, and 27x80km single-mode-fiber links), and also including laser phase
noise, except when in-line dispersion compensation is used. Furthermore, we
define a new metric, the nonlinear phase noise (NPN) metric, which is based on
the frequency resolved logarithmic perturbation models and explains the
interaction of CPR and PAS. We show that the NPN metric is highly correlated
with the performance of the system. Our results suggest that, in general, the
optimization of PAS in the nonlinear regime should always account for the
presence of a CPR algorithm. In this case, the reduction of the rate loss
(obtained by using sphere shaping and increasing the DM block length) turns out
to be more important than the mitigation of the nonlinear phase noise (obtained
by using constant-energy DMs and reducing the block length), the latter being
already granted by the CPR algorithm.Comment: Accepter for publication to the Journal of Lightwave Technologies on
January 202
Análise in vitro da distribuição de tensões em implantes angulados de diferentes comprimentos
: Neste trabalho apresenta-se um estudo realizado para avaliar computacionalmente ouso de implantes curtos em reabilitação mandibular total com base no Método dos ElementosFinitos. Em particular, verifica-se como o comprimento desses implantes influencia adistribuição de tensões durante a aplicação de cargas mastigatórias em reabilitaçõesmandibulares de acordo com o conceito All-on-4®
Efeitos biomecânicos da evolução do colesteatoma sobre a corda do tÃmpano
A otite média crónica pode levar ao aparecimento de um tumor benigno do ouvido, chamado colesteatoma. Esta patologia, se não for devidamente tratada, pode ter graves consequências. Uma delas pode resultar em paralisia facial se comprimir um ramo do nervo facial que atravessa o ouvido médio. Neste trabalho foram avaliadas as tensões exercidas do tumor contra o nervo. A maior tensão foi obtida na área de contacto entre o nervo e a bigorna.info:eu-repo/semantics/publishedVersio
- …