Analytical CPP in rotated energy-mapped stress space applied to von-Mises and Drucker-Prager yield surfaces

5 This study describes a simplified method to formulate the closest point projection (CPP) for associative 6 models. It represents the elastoplastic model on a rotated energy-mapped stress space (REMSS). The CPP in 7 conventional stress space does not give the closest point in Euclidean norm, but in energy norm. In REMSS 8 the correct return trajectory is a closest-point return. REMSS allows to find models that are analytically 9 solvable. The rotated stresses aim in simplifying the constitutive relation allowing to get analytical solutions 10 or applying the Newton's method at a smaller system of equations. The analytical solution is up to four 11 times faster than a standard numerical backward Euler algorithm. The rotated space described here allows 12 to drop one cylindrical coordinate, i.e., instead of using three coordinates (e.g. ξ, ρ and β) to represent a 13 yield surface in principal stress space, at most two are necessary (e.g. ξ and/or β). The analytical CPP 14 solution using the proposed method is described for Druker-Prager and von Mises models. This study also 15 discuss the numerical solution of modified hyperbolic Drucker-Prager. The proposed formulation is verified 16 by applying it to three finite element examples and the code is available on-line. Extent of the code proposed 17 here to elastoplastic calculations of other models is straightforward. 18 Keywords closest point projection, rotated energy-mapped stress space, computational plasticity, finite 19 elements, Mathematic

Simulador de sistemas de transmissão

The search for highly linear, efficient systems that can respond to many users has been one of the major concerns of telecommunications operators. In order to respond to all these needs, 5G communication systems have recently started to be developed. The transition to higher frequencies associated with these systems brings with it new challenges in transmitter design, such as the need for antenna arrays. These, in addition to being able to have a large number of elements, also cause the existence of electromagnetic coupling between them, making it very difficult to test them at the circuit level. Thus, this dissertation arises with the objective of developing a platform where it is possible to test, in a fast and userfriendly way, this type of systems. In the second chapter, some characteristics of antenna arrays are presented, reinforcing the need for the platform. The third chapter presents its development, serving as an instruction manual for someone who, in the future, wants to add new features to it. In the fourth chapter, the obtained results are presented and a tutorial is made for a future user of the platform. Finally, the conclusions and future work are presented.A procura de sistemas altamente lineares, eficientes e que consigam dar resposta a muitos utilizadores, tem sido uma das grandes preocupações dos operadores de telecomunicações. Para dar resposta a todas estas necessidades, começaram, recentemente, a ser desenvolvidos sistemas de comunicações 5G. A transição para frequências mais altas associada a estes sistemas traz consigo novos desafios no design dos transmissores, como por exemplo o facto de serem necessários arrays de antenas. Estes, para além de poderem ter um grande número de elementos, provocam, também, a existência de acoplamento eletromagnético entre eles, tornando-se, desta forma, muito difícil testá-los a nível do circuito. Surge, assim, esta dissertação com o objetivo de desenvolver uma plataforma onde seja possível testar, de forma rápida e amiga do utilizador, este tipo de sistemas. No segundo capítulo são apresentadas mais aprofundadamente algumas características dos arrays de antenas, reforçando a necessidade da plataforma. O terceiro capítulo apresenta o desenvolvimento da mesma, servindo como manual de instruções para alguém que, futuramente, lhe queira acrescentar funcionalidades. No quarto capítulo são apresentados os resultados obtidos e é feito um tutorial para um futuro utilizador da plataforma. Por fim são apresentadas as conclusões e o trabalho futuro.Mestrado em Engenharia Eletrónica e Telecomunicaçõe

Assessment of the quality of mobile telecommunications services

JEL Classification: L96; Y40Over the past decades, the telecommunications sector has grown both in terms of revenues, both in terms of number of clients, which in turn has meant that the demand for the quality of services provided by mobile network operators increased. Given the above, this thesis aims to assess how clients perceive the perceived quality of the mobile network operator service through a quality measurement tool adapted to the respective sector (SERVPERF). With regard to methodology, an online questionnaire was applied based on SERVPERF instrument developed by Cronin Jr. and Taylor (1992), adding some items due to the peculiarity of mobile telecommunications services. In order to process the data obtained, the Statistical Package for Social Sciences ("SPSS") version 22 was used exclusively, which allowed for various statistical calculations. With regard to the results, there is a general positive perception of the quality of mobile telecommunications services, highlighting the Communication dimension, but only with a very little significant difference regarding the Tariff dimension. In addition, and after having performed the Principal Component Analysis ("PCA") the initial eight dimensions became only three, namely: Service Provider, Accessibility and Comunication and Tangibility. Lastly, some recommendations were proposed to improve the perceived quality of service being studied, regarding a proximity policy, the implementation of the service, the disclosure / provision of information and the facilities.Ao longo das últimas décadas, o setor das telecomunicações tem crescido quer a nível de receitas, quer a nível do número de clientes, que por sua vez fez com que a exigência para com a qualidade dos serviços prestados pelos operadores de rede móvel aumentasse. Face ao exposto, a presente dissertação tem como objetivo principal avaliar como os clientes percecionam a qualidade percebida do serviço dos operadores de rede móvel através de uma ferramenta de medição de qualidade adaptada ao respetivo setor (SERVPERF). Relativamente à metodologia, foi aplicado um questionário via online baseado no instrumento SERVPERF desenvolvido por Cronin Jr. e Taylor (1992), acrescentando alguns itens devido à peculiaridade dos serviços de telecomunicações móveis. De forma a tratar os dados obtidos, recorreu-se exclusivamente ao programa Statistical Package for Social Sciences (“SPSS”) versão 22, o qual permitiu a realização de diversos cálculos estatísticos. No que diz respeito aos resultados, verifica-se de uma forma geral que a perceção da qualidade dos serviços de telecomunicações móveis é positiva, destacando-se a dimensão Communication, contudo apenas com uma diferença pouco significativa face à dimensão Tariff. Por último, foram propostas algumas recomendações de melhoria da qualidade percebida do serviço em estudo, relativamente a uma política de proximidade, à execução do serviço, à divulgação/disponibilização de informações e às instalações

On extending process monitoring and diagnosis to the electrical and mechanical utilities: an advanced signal analysis approach

This thesis is concerned with extending process monitoring and diagnosis to electrical and mechanical utilities. The motivation is that the reliability, safety and energy efficiency of industrial processes increasingly depend on the condition of the electrical supply and the electrical and mechanical equipment in the process. To enable the integration of electrical and mechanical measurements in the analysis of process disturbances, this thesis develops four new signal analysis methods for transient disturbances, and for measurements with different sampling rates. Transient disturbances are considered because the electrical utility is mostly affected by events of a transient nature. Different sampling rates are considered because process measurements are commonly sampled at intervals in the order of seconds, while electrical and mechanical measurements are commonly sampled with millisecond intervals. Three of the methods detect transient disturbances. Each method progressively improves or extends the applicability of the previous method. Specifically, the first detection method does univariate analysis, the second method extends the analysis to a multivariate data set, and the third method extends the multivariate analysis to measurements with different sampling rates. The fourth method developed removes the transient disturbances from the time series of oscillatory measurements. The motivation is that the analysis of oscillatory disturbances can be affected by transient disturbances. The methods were developed and tested on experimental and industrial data sets obtained during industrial placements with ABB Corporate Research Center, Kraków, Poland and ABB Oil, Gas and Petrochemicals, Oslo, Norway. The concluding chapters of the thesis discuss the merits and limitations of each method, and present three directions for future research. The ideas should contribute further to the extension of process monitoring and diagnosis to the electrical and mechanical utilities. The ideas are exemplified on the case studies and shown to be promising directions for future research.Open Acces

Actividade da enzima GSase do ciclo ureia-ornitina no xarroco (Halobatrachus didactylus): efeito da amónia ambiental: efeito de injecção com cortisol

Dissertação de mest., Biologia Marinha, Faculdade de Ciências e Tecnologia, Univ. do Algarve, 201

A State-Machine Model for Reliability Eliciting over Wireless Sensor and Actuator Networks

AbstractAdvances in communications and embedded systems have led to the proliferation of wireless sensor and actuator networks (WSANs) in a wide variety of application domains. One important key of many such WSAN applications is the needed to meet non-functional requirements (e.g., lifetime, reliability, time guarantees) as well as functional ones (e.g. monitoring, actuation). Some application domains even require that sensor nodes be deployed in harsh environments (e.g., refineries), where they can fail due to communication interference, power problems or other issues. Unfortunately, the node failures can be catastrophic for critical or safety related systems. State machines can offer a promising approach to separate the two concerns – functional and non-functional – bringing forth reliability exception conditions handling, by means of fault handling states. We develop an approach that allows users to define and program typical applications using their platform language, but also adds state machine logic to design, view and handle explicitly other concerns such as reliability. The experimental section shows a working deployment of this concept in an industrial refinery settin

O proêmio da Metafísica de Aristóteles: uma interpretação de Metaph. A1

Based on the notion of proem as exposed in Aristotle’s Rhetoric, we examine in detail Metaph. A1. Our goal is to understand the argument contained in this chapter, as we also endeavour to show how the Stagirite introduces with uttermost caution the theme of wisdom [σοφία], that which is the incarnation of the preeminent science in the first book of the Metaphysics. The attention we devote to the proem of this work is explained by the importance we attribute, unlike much of contemporary scholars, to σοφία, that is, the science of first causes and principles, which we consider to be, ultimately, the pivotal formulation of the supreme science in the Metaphysics

CityMii - An integration and interoperable middleware to manage a Smart City

Modern cities are supported by multiple heterogeneous IT systems deployed and managed by distinct agents. In general, those systems use old, dependent and non-standardized technologies, which make them legacy and incompatible systems. As smart cities are moving toward a fully centralized management approach, the lack of integration among systems raises several problems. Since they are independent, it is not easy to correlate information from different systems and put it together to work in order to achieve application goals. The collaboration among different systems enables an agent to offer new functionalities (services or just information about the city) that cannot be provided by any of these systems working as individual entities. The goal of this paper is to propose an integration middleware to support the management of Smart Cities in a dynamic, transparent and scalable way. The proposed middleware intends to support interoperability among different systems operating in a city.info:eu-repo/semantics/publishedVersio

Denoising Autoencoder-based Defensive Distillation as an Adversarial Robustness Algorithm

Adversarial attacks significantly threaten the robustness of deep neural networks (DNNs). Despite the multiple defensive methods employed, they are nevertheless vulnerable to poison attacks, where attackers meddle with the initial training data. In order to defend DNNs against such adversarial attacks, this work proposes a novel method that combines the defensive distillation mechanism with a denoising autoencoder (DAE). This technique tries to lower the sensitivity of the distilled model to poison attacks by spotting and reconstructing poisonous adversarial inputs in the training data. We added carefully created adversarial samples to the initial training data to assess the proposed method's performance. Our experimental findings demonstrate that our method successfully identified and reconstructed the poisonous inputs while also considering enhancing the DNN's resilience. The proposed approach provides a potent and robust defense mechanism for DNNs in various applications where data poisoning attacks are a concern. Thus, the defensive distillation technique's limitation posed by poisonous adversarial attacks is overcome.Comment: This paper have 4 pages, 3 figures and it is accepted at the Ada User journa

Testando a teoria de hierarquização de fontes de financiamento nas empresas brasileiras

O presente trabalho testa se a teoria conhecida como Pecking Order Theory ou Teoria de Hierarquização de Fontes de Financiamento (THFF) fornece explicação empírica para a estrutura de capital das empresas no Brasil. De acordo com essa teoria, a estrutura de capital seria resultante de um funding hierarquizado, em que os recursos gerados internamente teriam prioridade, seguidos pela emissão de dívida e, apenas em último caso, pela emissão de ações. Em sua forma forte, a THFF sustenta que emissões de ações nunca ocorreriam, enquanto, em sua forma fraca, volumes limitados de emissões são aceitáveis. A metodologia do estudo empírico envolve regressões em cross-section e testes de hipóteses para especificações oriundas da teoria em questão para as formas forte e fraca. Os resultados levam a concluir que a teoria testada, em sua forma fraca, é aplicável às empresas brasileiras, o mesmo não ocorrendo com a sua forma forte. Mostram, também, que a qualidade de ajustamento das regressões para o Brasil é signifi cativamente melhor do que aquelas relatadas para empresas norte- americanas e que as empresas brasileiras parecem estar mais próximas da forma forte da THFF do que as norte-americanas. A amostra consiste de 132 empresas de capital aberto e os dados contábeis referem-se a 2001.The paper tests if the theory known as Pecking Order Theory provides empirical explanations for the capital structure of Brazilian firms. According to this theory, the capital structures would result from a hierarchy of fi nancial decisions, in which internally generated resources would have first priority, followed by debt issues and, as a last resort only, by equity issues. In its strong form, the Pecking Order sustains that equity issues would never occur, whereas in its weak form, limited amounts of issues are acceptable. The methodology adopted in this empirical study involves cross-sectional regressions and the testing of hypotheses based on the underlying theory in its strong and weak forms. The results led to the conclusion that the tested theory, in its weak form, is applicable to Brazilian firms, but that the same does not happen in its strong form. The results also show that the goodness of fit of the Brazilian regressions are significantly better than those reported for American fi rms and that Brazilian firms seem to be closer to the Pecking Order’s strong form than the American ones. The sample involves 132 publicly listed firms and the accounting data refer to 2001