Iteration of quadratic maps on matrix algebras

We study the iteration of a quadratic family in the algebra of 2 × 2 real matrices, parameterized by a matrix C. We analyze and classify the existing cycles (periodic orbits) and their dependence on the parameter matrix. We discuss how new dynamical phenomena occur as a consequence of the noncommutativity of the matrix product. In particular, we show that the commutator of the initial condition with parameter matrix C has a decisive role in the overall dynamics

Renormalization in a Lorentz-violating model and higher-order operators

The renormalization in a Lorentz-breaking scalar-spinor higher-derivative model involving $\phi^4$ self-interaction and the Yukawa-like coupling is studied. We explicitly de- monstrate that the convergence is improved in comparison with the usual scalar-spinor model, so, the theory is super-renormalizable, with no divergences beyond four loops. We compute the one-loop corrections to the propagators for the scalar and fermionic fields and show that in the presence of higher-order Lorentz invariance violation, the poles that dominate the physical theory, are driven away from the standard on-shell pole mass due to radiatively induced lower dimensional operators. The new operators change the standard gamma-matrix structure of the two-point functions, introduce large Lorentz-breaking corrections and lead to modifications in the renormalization conditions of the theory. We found the physical pole mass in each sector of our model.Comment: 20 pages, 5 figures. New version with modifications in the renormalized Lagrangian. To be published in EPJ

Is professionals in a virtual is context: the “to do what?” component of a qualitative study

The present paper plans shares the results of a study that was driven by the awareness that few activities and professions have seen such a rapid change over the past years as those related to the field of Information Systems (IS). According to these principles, this paper aims to present findings and propositions about the evolution of the context where these activities are performed, in order to contribute to the ongoing debate about IS professionals and IS function development. Despite the fact that the main concern of the global research project was people (IS professionals - the “who” part of the project) this paper is purposeful in the IS management activities (the IS function or the “to do what” part of the project). Ontological and epistemological fundamentals of interpretative research based the research process. Theories and models were derived from the empirical material gained from near 30 leading experts from the IS area in Portugal, both academic and practitioners. Grounded theory has been used as supporting method and semi-structured interview was selected as a technique to collect data. To understand the transformation process, forces that affect different IS dimensions have been identified and a dynamic model that supports IS context transformation is proposed. This model aims to explain how relations between different actors, IS tasks, roles and responsibilities have evolved and to predict scenarios in the present virtualized context where IS activities are performed

Evaluation of wsn technology for dependable monitoring in water environmnts

Tese de mestrado, Engenharia Informática (Arquitetura e Redes de Computadores) Universidade de Lisboa, Faculdade de Ciências, 2019Few problems arise when trying to reliably monitor a surrounding environment by the use of sensors and a wireless network to disseminate the information gathered. In the context of an aquatic environment, the undulation and the low predictability of the surrounding environment could cause faults in the transmission of data. The initial motivation for the work developed in this thesis was the Aquamon project. Aquamon is a project that has as objective the deployment of a dependable Wireless Sensor Network (WSN) for the purposes of water quality monitoring and the study of tidal movements. Therefore, Aquamon, like any other WSN will have to go through the process of choosing a technology that meets its application requirements as well as the requirements imposed by the deployment environment. WSNs can have constraints when it comes to the Quality of Service and availability it can provide. These networks generally have a set requirements that need to be satisfied. Thus, there needs to be a selection of one (or multiple) wireless technologies that can satisfy said requirements. This selection process is usually done in a ad-hoc way, weighting the advantages and disadvantages of different possible solutions with respect to some requirements, often using empirical knowledge or simply dictated by the designer’s preference for some particular technology. When several functional and non-functional requirements have to be addressed, finding an optimal or close to optimal solution may become a hard problem. This thesis proposes a methodology for addressing this optimization problem in an automated way. It considers various application requirements and the characteristics of the available technologies (including Sigfox, LoRa, NB-IoT, ZigBee and ZigBee Pro) and delivers the solution that better satisfies the requirements. It illustrates how the methodology is applied to a specific use case of WSN-based environmental monitoring in the Seixal Bay

Avicena e as ciências mistas

Some of Aristotle’s texts (Physics II,2; Posterior Analytics I, 7, 9 and 13) mention some sciences (astronomy, harmony, optics and mechanics – the last one only in Posterior Analytics) in the context of the distinction between physics and mathematics (in Physics), the impossibility of using the demonstrations of one science in another one (metabasis) and the distinction between proofs of what and why (in Posterior Analytics). These texts allowed his commentators – especially the Arabic and Latin ones – to approach the epistemic status of such sciences. The present study seeks to examine how Avicenna – or more precisely, the Latin Avicenna – dealt with this issue in Liber primum naturalium, and what he would have added to Aristotle’s text. In this regard, it is possible to point out to the addition of at least two more sciences to Aristotle’s list (science of the spheres in motion and science of weights), a formal definition of this type of sciences, implying their mixed nature (Avicenna refers to astronomy): “this science is as if it were mixed from the natural and the disciplinary [mathematics] ones. As the pure disciplinary one is abstract, in no way in matter, and this one is as if inserting the abstract one in designated [determined] matter”. It is also noteworthy a terminology that cannot be found in Aristotle’s text: “mixed science” – in the Arabic text, “participating” (mushtarak) or “compounded” (murakkab) science -, “pure and inserted science”, “abstraction”.Algunos textos de Aristóteles (Física II,2; Segundos Analíticos I,7,9 y 13) mencionan ciertas ciencias (astronomía, armónica, óptica y mecánica - esta última a penas en los Segundos Analíticos) a propósito de la distinción entre física y matemática (Física), de la imposibilidad de usar demostraciones de una ciencia en otra (metábase) y de la distinción entre una prueba de qué y de por qué (Segundos Analíticos). Estos textos indujeron a los comentaristas, especialmente árabes y latinos, a ocuparse de la situación epistémica de estas ciencias. En esta comunicación, se pretende examinar como Avicena - más precisamente, el Avicena latino - trata este tópico en Liber primus naturalium, y aquello que adiciona al texto de Aristóteles. En este sentido, es posible indicar la adición de dos ciencias más en la lista de Aristóteles (la ciencia de las esferas en movimiento y la ciencia de los pesos), una definición formal de este tipo de ciencias, como si implicando su carácter misxto (Avicena se refiere a la astronomía): "esta ciencia es como si fuera mixta de la natural y de la disciplinar [matemática]. Visto que la disciplinar pura es abstracta, de ningún modo en la materia, y ésta es como que insertando esta abstracta en la materia designada [determinada]". Obsérvese también terminología que no se encuentra en el texto de Aristóteles: "ciencia mixta" - en el texto árabe ciencia "participante" (mushtarak) o "compuesta" (murakkab)-, "ciencia pura e insertada", "abstracción".Alguns textos de Aristóteles (Física II, 2; Segundos Analíticos I, 7, 9 e 13) mencionam certas ciências (astronomia, harmônica, ótica e mecânica, esta última apenas nos Segundos Analíticos) a propósito da distinção entre física e matemática (na Física), da impossibilidade de usar demonstrações de uma ciência em outra (metábase) e da distinção entre uma prova de quê e de por quê (nos Segundos Analíticos). Estas passagens deram ocasião a que seus comentadores, sobretudo árabes e latinos, se ocupassem com a situação epistêmica de tais ciências. Pretende-se nesta comunicação examinar como Avicena, ou mais precisamente o Avicena Latino, trata deste tópico no Liber primus naturalium e o que acrescentaria ao texto de Aristóteles. Seria possível, quanto a isto indicar pelo menos o acréscimo de mais duas ciências à lista de Aristóteles (ciência das esferas em movimento e ciência dos pesos), uma definição formal deste tipo de ciências, como implicando seu caráter misto (Avicena está falando da astronomia): “esta ciência é como que se fosse mista da natural e da disciplinar [matemática]. Visto que a disciplinar pura é abstrata, de modo nenhum na matéria, e esta é como que inserindo esta abstrata na matéria designada [determinada]”. Note-se também uma terminologia não encontrada no texto de Aristóteles: “ciência mista” – no texto árabe ciência “participante” (mushtarak) ou “composta” (murakkab) –, “ciência pura e inserida”, “abstração”