Conversor multinível NPC de cinco níveis como ondulador de tensão ligado à rede

O crescimento da utilização de accionamentos electromecânicos de velocidade variável entre outros dispositivos que necessitam de tensões elevadas, na ordem dos kV e com elevados níveis de qualidade, despertou o interesse pelos conversores multinível. Este tipo de conversor consegue alcançar elevadas tensões de funcionamento e simultaneamente melhorar a qualidade das formas de onda de tensão e corrente nas respectivas fases. Esta dissertação de mestrado tem por objectivo apresentar um estudo sobre o conversor multinível com díodos de ligação ao neutro (NPC – neutral point clamped), de cinco níveis utilizado como ondulador de tensão ligado à rede. O trabalho começa por desenvolver o modelo matemático do conversor multinível com díodos de ligação ao neutro de cinco níveis e a respectiva interligação com a rede eléctrica. Com base no modelo do conversor são realizadas simulações numéricas desenvolvidas em Matlab-Simulink. Para controlo do trânsito de energia no conversor é utilizando controlo por modo de deslizamento aplicado às correntes nas fases. As simulações efectuadas são comparadas com resultados de simulação obtidos para um ondulador clássico de dois níveis. Resultados de simulação do conversor multinível são posteriormente comparados com resultados experimentais para diferentes valores de potências activa e reactiva. Foi desenvolvido um protótipo experimental de um conversor multinível com díodos de ligação ao neutro de cinco níveis e a respectiva electrónica associada para comando e disparo dos semicondutores de potência.The increased use of variable speed electromechanical drives and other devices that require high voltages in the order of kV and high levels of quality, aroused interest in multilevel converters. This type of convertercan achieve high voltages while improving the quality of the waveforms of voltageand current in the respective phases. This dissertation aims to present a study of the multilevel converter with diodes connected to neutral phase (NPC – Neutral Point Clamped), five levels used as a voltage inverter connected to the network. This study begins by developing the mathematical model of the multilevel converter with diodes connecting the neutral of five levels and their interconnection with the network. Based on the model ofthe converter are performed out numerical simulations developed in Matlab-Simulink. To control the transit of energy in the converter is by using sliding mode control applied to the phase currents. The simulations are compared with simulation results obtained for a classical two-level inverter. Simulation results of the multilevel converter are then compared with experimental results for different values of active and reactive power. It was developed an experimental prototype of a multilevel converter with diodes connecting the neutral of five levels and their associated electronics for control and firing of the power semiconductors

Rural (In)Securities:: Resettlement, Control and “Development” in Angola (1960s–1970s)

Nach dem Ausbruch organisierter anti-kolonialer Gewalt während der frühen sechziger Jahre suchten portugiesische imperiale und koloniale Akteure nach politisch-militärischen Strategien, die Sicherheit, rudimentäre Sozialfürsorge und Entwicklung kombinierten. Diese speziische Kombination war ein Wesensmerkmal des Spätkolonialismus. Neben Strategien zur Bevölkerungskontrolle, „psychologischen Aktivitäten“ oder einer Sozialgesetzgebung entwickelte sich ländliche Entwicklungspolitik zu einem zentralen Instrument der spätkolonialen Sicherheitspolitik. Ausgehend von der Analyse zweier zentraler Dokumente, die ländliche Entwicklungspolitik propagierten, zeigt der Artikel, wie ländliche Regionen zu einem wesentlichen Austragungsort von militärisch-politischen Sicherheitsstrategien wurden, die viele Elemente ländlicher Entwicklungspolitik enthielten

History & Society: The work of Michael Mann

This forum is the outcome of the symposium History & Society: The Work of Michael Mann, organized by Miguel Bandeira Jerónimo and António Costa Pinto at the Institute of Social Sciences of the University of Lisbon, on 8 June 2012.1 With the support of Edições 70 (of Almedina Group), the publishing house responsible for the Portuguese edition of Fascists (Mann, 2011)2 , this symposium gathered several Portuguese scholars interested in engaging critically with Professor Mann’s oeuvre, from a multidisciplinary perspective and from diverse thematic, historiographical, and historical standpoints

Empires, globalizations, and historical sociology: an interview with Michael Mann

I n this brief but revealing interview with Professor Michael Mann we address and assess the fundamental novelties offered by volumes iii and iv of his magnum opus The Sources of Social Power, focusing on two main issues. First, we emphasize conceptual and analytical questions. Second, we highlight two of the major themes of volumes iii and iv: the polymorphous and segmental empires and globalizations, their historical formation and relationship. We conclude by asking Professor Mann about his take on Historical Sociology, a crucial yet downplayed tradition in Human and Social Sciences. Michael Mann’s work is a clear demonstration of the imperative to recognize the centrality of this tradition. It is also an exemplary contribution to all the efforts that seek to place Historical Sociology at the fore of our individual and collective intellectual research

Restoring Order, Inducing Change: Imagining a “New (Wo)man” in the Belgian Colonial Empire in the 1950s*

Kennzeichnend für den kolonialen Kontext für die Zeit nach dem Zweiten Weltkrieg ist einespezifische Ausdrucksweise im Zusammenhang mit sozialen Interventionen. Europäische Kolonialadministrationen planten auf unterschiedliche Wiese die Erneuerung imperialer politischer und moralischer Ökonomien. Diese Dynamik manifestierte sich in der Durchsetzung einer Entwicklungs- und Wohlfahrtsrhetorik sowie entsprechender politischer Vorgaben. Die soziale Beeinflussung von Individuen und Kollektiven auf der Grundlage von Ideen vom “Neuen Menschen” wurden von einer ganzen Bandbreite an Institutionen und Netzwerken betrieben. Diese verfolgten nicht nur divergierende Ziele, sondern setzten unterschiedliche Ressourcen ein. So beanspruchten im belgischen Kolonialreich viele Akteure das savoir-développer oder das savoirtransformer für sich, um ihre Experimente zur „umfassenden gesellschaftlichen Entwicklung“ zu rechtfertigen. Obgleich sie als Wandel ausgelegt wurden, zielten diese Projekte auf den Erhalt der bestehenden Ordnung ab. Dieser Beitrag befasst sich mit dieser Dynamik, indem er die Rolle internationaler und inter-imperialer Organisationen in den Blick nimmt.The post-WWII momentum was characterized by the emergence of specific languages andrepertoires of societal intervention in colonial contexts. Given the new (geo)political circumstances, renewed imperial political and moral economies were envisaged by European colonial authorities, albeit in dissimilar ways. The establishment of a developmentalist and welfarist rhetoric and the formulation of related policies, which entailed political, economic, and sociocultural calculations and objectives, was one manifestation of these dynamics. The efforts of social engineering, at individual and collective levels, in which the imagination of ‘new (wo) man’ and communities was fundamental, were carried by multiple institutions and networks, with diverse motivations, resources and agendas, operating on many levels. In the Belgium colonial empire, the savoir‑développer and the savoir-transformer were claimed by many, in order to advocate or justify experiments in “comprehensive social development”, mainly designed to induce change with a view to restore order. This paper addresses these issues and explores this case, emphasizing the significant role played by international, interimperial organizations

Assessing the impact of industry in M&A success

The purpose of this thesis is to assess whether a company’s industry has a significant impact on the success rate of an M&A deal. The theoretical analysis is divided in three main determinants which are believed to support differences in performance – Premiums, Revenues & Costs and Integration. The empirical study regressed the Premiums and CARs for three distinct industries. The main results suggest both the acquirer’s industry and the premiums paid are, as hypothesised, relevant when explaining M&A success. Furthermore, evidence shows knowledge-intensive firms – Pharmaceutical and Software - tend to pay higher premiums but achieve better CARs

Business models reinvention: from staffing to management consulting case

Despite the high market demand in the staffing business, the dissatisfaction and volatility of employees is a constant risk and the value proposition for customers brings limited value. Besides being purely transactional, this business model makes the creation and development of assets unfeasible as it lacks regulation and is still perceived as one that can be easily imitated. In order to reverse the situation and considering that the management consulting business model is relatively similar in terms of means and is perceived as having sustainable competitive advantages, the objective of this investigation was to propose the transformation of the business model from staffing to management consulting. A total of 62 professionals from 34 staffing and management consulting companies were interviewed, revealing details regarding the various areas of the value chain. A comparative financial analysis and model validation was also performed. Literature review, as well as the analysis of the interviews was supported by text mining techniques. The conceptual model and the conclusions obtained in parallel are certainly useful for the academy, but also for companies and society, since the transformation of the business model represents a combination of different working conditions and formats in the face of current events. There are several findings, but it should be highlighted that in management consulting the profit per employee is on average 87% higher when compared with a staffing employee. Recommendations are also provided to push the limits of thinking, generate new options and, ultimately, to enhance the competitive advantages of service companies.Apesar da elevada procura de mercado, no negócio de staffing a insatisfação e volatilidade dos colaboradores é um risco atual e a proposta de valor para os clientes aporta valor limitado. Além de puramente transicional, este modelo de negócio inviabiliza a criação e desenvolvimento de ativos, carece de regulamentação, sendo ainda percecionado como facilmente imitável. No sentido de inverter a situação e sendo o modelo de negócio de management consulting relativamente similar em termos de meios e percecionado com vantagens competitivas sustentáveis, foi objetivo desta investigação uma transformação do modelo de negócio de staffing para management consulting. Um total de 62 profissionais de 34 empresas de staffing e management consulting foram entrevistados revelando detalhes relativos às várias dimensões da cadeia de valor. Foi ainda realizada uma análise financeira comparativa e a validação modelo. A revisão de literatura, assim como a análise das entrevistas, foi suportada por técnicas de text mining. O modelo concetual e as conclusões paralelamente obtidas são certamente úteis para o meio académico, mas também para as empresas e para a sociedade, dado que a transformação do modelo de negócio representa igualmente uma combinação de condições e formatos de trabalho diferentes face à atualidade. Existem várias conclusões, mas é de salientar que em management consulting o lucro por colaborador é em média 87% superior a um colaborador de staffing. São ainda fornecidas recomendações para ampliar os limites do pensamento, para gerar novas opções e, em última análise, para potenciar o aumento de vantagens competitivas das empresas de serviços

Internacionalismo y políticas y políticas de misión en el imperio colonial portugués (1885-1930)

This article addresses the politics and the policies of mission in the Portuguese colonial empire in the late nineteenth and early twentieth centuries. It explores the extent to which such policies were shaped by the international, transnational, and inter-imperial dynamics of political and religious internationalisms embraced by sectors of the Catholic and Protestant churches.Este artículo aborda la política y las políticas de misión en el imperio colonial portugués a fines del siglo xix y principios del xx. Explora en qué medida dichas políticas eran configuradas por las dinámicas internacionales, trasnacionales e interimperiales de las políticas y religiones abarcados por sectores de las Iglesias Católica y Protestante

INTERNATIONALISMS AND THE POLITICS AND POLICIES OF MISSION IN THE PORTUGUESE COLONIAL EMPIRE (1885-1930)

This article addresses the politics and the policies of mission in the Portuguese colonial empire in the late nineteenth and early twentieth centuries. It explores the extent to which such policies were shaped by the international, transnational, and inter-imperialdynamics of political and religious internationalisms embraced by sectors of the Catholic and Protestant churches