O Fausto traduzido por A. F. Castilho: entre a tradução e a criação

Polissema: Revista de Letras do ISCAP 2001/N.º 1 - Tradução

Complex-order forced van der Pol oscillator

In this paper we consider a complex-order forced van der Pol oscillator. The complex derivative Dα1jβ, with α, β ∈ ℝ+, is a generalization of the concept of an integer derivative, where α = 1, β = 0. The Fourier transforms of the periodic solutions of the complex-order forced van der Pol oscillator are computed for various values of parameters such as frequency ω and amplitude b of the external forcing, the damping μ, and parameters α and β. Moreover, we consider two cases: (i) b = 1, μ = {1.0, 5.0, 10.0}, and ω = {0.5, 2.46, 5.0, 20.0}; (ii) ω = 20.0, μ = {1.0, 5.0, 10.0}, and b = {1.0, 5.0, 10.0}. We verified that most of the signal energy is concentrated in the fundamental harmonic ω0. We also observed that the fundamental frequency of the oscillations ω0 varies with α and μ. For the range of tested values, the numerical fitting led to logarithmic approximations for system (7) in the two cases (i) and (ii). In conclusion, we verify that by varying the parameter values α and β of the complex-order derivative in expression (7), we accomplished a very effective way of perturbing the dynamical behavior of the forced van der Pol oscillator, which is no longer limited to parameters b and ω.

Projeto de Simulação Empresarial: a experiência no ISCAP

Este artigo descreve um estudo levado a cabo no Instituto Superior de Contabilidade e Administração do Porto – Instituto Politécnico do Porto (ISCAP-IPP), no curso de Licenciatura de Contabilidade e Administração nas unidades curriculares de Projeto de Simulação Empresarial (PSE) I e II, no ano letivo de 2012/2013. Este estudo tem como base um inquérito efetuado a 60 alunos em PSE I e a 60 alunos de PSE II. O inquérito tenta aferir a perceção dos alunos para questões sobre competências gerais e específicas, consideradas importantes para os gestores e contabilistas no presente. Os resultados transmitem que os alunos reconhecem que a frequência das unidades curriculares permite o reforço e melhoria das competências adquiridas ao longo do curso. Estas conclusões corroboram os de Adler e Milne (1997) que nos dizem que os alunos concordam que a aprendizagem orientada para a ação ajuda na melhoria das suas competências e conhecimentos.

Buckling strength of adhesively-bonded single and double-strap repairs on carbon-epoxy structures

This work reports on an experimental and finite element method (FEM) parametric study of adhesively-bonded single and double-strap repairs on carbon-epoxy structures under buckling unrestrained compression. The influence of the overlap length and patch thickness was evaluated. This loading gains a particular significance from the additional characteristic mechanisms of structures under compression, such as fibres microbuckling, for buckling restrained structures, or global buckling of the assembly, if no transverse restriction exists. The FEM analysis is based on the use of cohesive elements including mixed-mode criteria to simulate a cohesive fracture of the adhesive layer. Trapezoidal laws in pure modes I and II were used to account for the ductility of most structural adhesives. These laws were estimated for the adhesive used from double cantilever beam (DCB) and end-notched flexure (ENF) tests, respectively, using an inverse technique. The pure mode III cohesive law was equalled to the pure mode II one. Compression failure in the laminates was predicted using a stress-based criterion. The accurate FEM predictions open a good prospect for the reduction of the extensive experimentation in the design of carbon-epoxy repairs. Design principles were also established for these repairs under buckling.

Real-time scheduling with resource sharing on heterogeneous multiprocessors

Consider the problem of scheduling a task set τ of implicit-deadline sporadic tasks to meet all deadlines on a t-type heterogeneous multiprocessor platform where tasks may access multiple shared resources. The multiprocessor platform has m k processors of type-k, where k∈{1,2,…,t}. The execution time of a task depends on the type of processor on which it executes. The set of shared resources is denoted by R. For each task τ i , there is a resource set R i ⊆R such that for each job of τ i , during one phase of its execution, the job requests to hold the resource set R i exclusively with the interpretation that (i) the job makes a single request to hold all the resources in the resource set R i and (ii) at all times, when a job of τ i holds R i , no other job holds any resource in R i . Each job of task τ i may request the resource set R i at most once during its execution. A job is allowed to migrate when it requests a resource set and when it releases the resource set but a job is not allowed to migrate at other times. Our goal is to design a scheduling algorithm for this problem and prove its performance. We propose an algorithm, LP-EE-vpr, which offers the guarantee that if an implicit-deadline sporadic task set is schedulable on a t-type heterogeneous multiprocessor platform by an optimal scheduling algorithm that allows a job to migrate only when it requests or releases a resource set, then our algorithm also meets the deadlines with the same restriction on job migration, if given processors 4×(1+MAXP×⌈|P|×MAXPmin{m1,m2,…,mt}⌉) times as fast. (Here MAXP and |P| are computed based on the resource sets that tasks request.) For the special case that each task requests at most one resource, the bound of LP-EE-vpr collapses to 4×(1+⌈|R|min{m1,m2,…,mt}⌉). To the best of our knowledge, LP-EE-vpr is the first algorithm with proven performance guarantee for real-time scheduling of sporadic tasks with resource sharing on t-type heterogeneous multiprocessors.

Avaliação da Perceção dos diferentes Graus de Maitland, na Região Lombar, entre Estudantes e Fisioterapeutas

Introdução – A perceção dos alunos acerca dos diferentes graus de Maitland quando estão a aprender a mobilizar a coluna vertebral não são conhecidas, no entanto esta informação ajudaria no desenvolvimento de estratégias de ensino/aprendizagem para que a sua aplicação seja segura e eficaz. Objetivo - Comparar a perceção dos diferentes graus na realização do movimento postero-anterior central, entre alunos e fisioterapeutas e alunos entre si. Métodos – No presente estudo observacional, analítico transversal, participaram 29 estudantes, divididos em três subgrupos, GA2 (n= 8); GA3 (n = 10) e GA4 (n = 11) e 12 fisioterapeutas. Todos os participantes realizaram num indivíduo assintomático, 5 oscilações, de cada grau, no segmento de L3. Para a recolha dos dados foi utilizado o sistema BioPlux research e para a sua análise o Software Acqknowledge, versão 3,9. O teste de Man-Whitney foi utilizado para determinar as diferenças entre alunos e fisioterapeutas na força, ritmo e amplitude dos 4 graus, e o teste Kruskal Wallis, para comparar os alunos dos diferentes anos, seguido dos testes Post Hoc de Dunn para analisar as variáveis amplitude e força entre os subgrupos. Resultados – Apenas se verificaram diferenças estatísticas entre os alunos e fisioterapeutas no que diz respeito à força na realização do grau IV (p=0,045) e entre os grupos GA2 e GA4 quanto à amplitude executada no grau I (p=0.018) e II (p=0.037) e na força aplicada no grau I (p=0.02) e III (p=0.031), nos quais os alunos do 2º ano realizaram menor amplitude e força que os do 4º ano. Conclusão -Verificaram-se diferenças na perceção da força no grau IV entre alunos e fisioterapeutas. Os alunos do 2º e 4º anos diferem entre si nos graus I e II quanto à amplitude e nos graus I e III quanto à força.

Arc exchange systems and renormalization

We exhibit the construction of stable arc exchange systems from the stable laminations of hyperbolic diffeomorphisms. We prove a one-to-one correspondence between (i) Lipshitz conjugacy classes of C(1+H) stable arc exchange systems that are C(1+H) fixed points of renormalization and (ii) Lipshitz conjugacy classes of C(1+H) diffeomorphisms f with hyperbolic basic sets Lambda that admit an invariant measure absolutely continuous with respect to the Hausdorff measure on Lambda. Let HD(s)(Lambda) and HD(u)(Lambda) be, respectively, the Hausdorff dimension of the stable and unstable leaves intersected with the hyperbolic basic set L. If HD(u)(Lambda) = 1, then the Lipschitz conjugacy is, in fact, a C(1+H) conjugacy in (i) and (ii). We prove that if the stable arc exchange system is a C(1+HDs+alpha) fixed point of renormalization with bounded geometry, then the stable arc exchange system is smooth conjugate to an affine stable arc exchange system.

Building Smarter Cities through Social Entrepreneurship

The objective of the present study is to examine the extent to which social ventures are able to increase the smartness of the cities. To achieve this goal, we adopt a qualitative approach, based on the case study method to obtain valuable insights about different characteristics and strategies of Cais (a non-profit association dedicated to help disadvantaged people in urban areas). By focusing on the analysis of the Cais activities, we assess whether its social intervention match the dimensions proposed by Giffinger et al. (2007) to rank smart cities’ performance, namely if it has smart: (i) economy; (ii) people; (iii) governance; (iv) mobility; (v) environment; and (vi) living. The research shows that the action pursued comprises elements from all the above mentioned dimensions. Further, the analysis reveals that Cais reinforces the smartness of the city where it acts (attributes such as living, economy, people, and environment).