1,191 research outputs found
sl_2 Gaudin model with Jordanian twist
sl_2 Gaudin model with Jordanian twist is studied. This system can be
obtained as the semiclassical limit of the XXX spin chain deformed by the
Jordanian twist. The appropriate creation operators that yield the Bethe states
of the Gaudin model and consequently its spectrum are defined. Their
commutation relations with the generators of the corresponding loop algebra as
well as with the generating function of integrals of motion are given. The
inner products and norms of Bethe states and the relation to the solutions of
the Knizhnik-Zamolodchikov equations are discussed.Comment: 22 pages; corrected typo
Apostar na energia geotérmica na Região Autónoma dos Açores
A secção UAciência é coordenada pelo Professor Universitário Armindo Rodrigues.[…].
A exploração de águas quentes para fins terapêuticos e de lazer, associadas às manifestações dos sistemas hidrotermais, tem vindo a crescer fortemente nos Açores, nomeadamente na ilha de São Miguel. No entanto, o potencial disponível é muito elevado e só uma pequeníssima parte está a ser aproveitada. Enquanto nos casos dos recursos geotérmicos de alta e baixa entalpia estamos cingidos à proximidade do recurso (proximidade ao reservatório), no âmbito da muito baixa entalpia, o recurso está presente em qualquer lado. As bombas de calor geotérmicas, pelo uso do calor da Terra através de sondas geotérmicas (instaladas entre a superfície e aproximadamente os 200 metros) permitem o fornecimento alternado de calor e frio às habitações, usando a mesma instalação; isto é, no Inverno retiramos calor da Terra e no Verão devolvemos o calor à Terra.
[…].info:eu-repo/semantics/publishedVersio
Valuable, rare, inimitable resources and organization (VRIO) resources or valuable, rare, inimitable resources (VRI) capabilities: what leads to competitive advantage?
The resource-based view (RBV) argues that valuable, rare, inimitable resources and organization (VRIO) lead to competitive advantage. Dynamic capabilities (DC) are a comparatively new field and the related literature is mainly conceptual. Capabilities can be considered as the firm’s routines and processes. We argue that the “O” in VRIO refers to DC. DCs are the “organization” needed to transform bundles of resources into competitive advantage. Consequently, does competitive advantage stem from VRIO resources or from VRI capabilities? Through a case study we analyzed the development of one capability in a medium-sized Portuguese footwear manufacturer. After reviewing the process of development of the capability, we performed a VRIO test for each of the resources it exploits and a VRI test of the capability. We can conclude that none of the resources contributing to the capability are VRIO, but the capability is VRI
Education, development and new learning in Europe: the portuguese case
Actualmente, Portugal enfrenta numerosos desafios e está a apostar, segundo as directrizes europeias, na formação dos recursos humanos, novas tecnologias e inovação como ingredientes essenciais para enfrentar e integrar a economia global. Isto implica, invariavelmente, alterações significativas na educação, formação e ensino, e uma remodelação das aprendizagens rumo à ambicionada sociedade do conhecimento.Actually Portugal has been confronting many challenges according to European Board rules tied to the formation of the human resource, the new technolo-gies and the innovations, as essentials tools to face and to integrate a global economy. This has been involving significant reformulations in education, teacher formation and teaching as well as a reformulation in the learning in the direction to an ambitious society of Knowledge
Information and knowledge society in the European Union: priorities of the Lisbon Strategy
Actualmente, vivemos na era da "Revolução Digital". Na verdade, os últimos dez anos têm assistido a uma difusão, sem precedentes, das Tecnologias da Informação e da Comunicação (TIC). Perante a globalização e a celeridade das mudanças tecnológicas, a União Europeia lançou a Estratégia de Lisboa, em 2000, com um objectivo estratégico: «transformar a Europa na economia baseada no conhecimento mais dinâmica e competitiva do mundo». Neste contexto, a Estratégia de Lisboa reconhece a importância das TIC no estímulo à competitividade, à inovação, na sociedade da informação e do conhecimento, e na economia baseada no conhecimento.Nowadays we live in 'Digital Revolution' era. In fact, the last ten years has witnessed an unprecedented diffusion of Information and Communication Technologies (ICT). Facing globalisation and faster technological change, European Union has launched the Lisbon Strategy, in 2000, who aim a strategic goal: «to become the most competitive and dynamic knowledge-based economy in the world». In this context, the Lisbon Strategy rightly recognises and values the importance of ICT in stimulating competitiveness and innovation and in the information and knowledge-based economy and society
China's special economic zones in Africa: context, motivations and progress
As more and more countries set foot in Africa, there is a growing attention on China’s role and engagement in the region. The approaches are very diverse and if some are more skeptical, others praise factors that particularly shape China’s current move to Africa such as a focus on development cooperation and on establishing strategic partnerships. These would also add that China has had a very positive and influential role in Africa through aiding many countries to solve imminent problems and to assist with knowledge transfer. In this paper, we first discuss the context of the launching of Special Economic Zones in Africa by examining the historic development of the Sino-Africa relationship, and analyze China’s motivations for establishing the Special Economic Zones in the continent. Finally, we present the latest progress of the Special Economic Zones’ development and discuss how they contribute toward the presence of China in Africa.info:eu-repo/semantics/publishedVersio
Uncertainty propagation in inverse reliability-based design of composite structures
An approach for the analysis of uncertainty propagation in reliability-based design optimization of composite laminate structures is presented. Using the Uniform Design Method (UDM), a set of design points is generated over a domain centered on the mean reference values of the random variables. A methodology based on inverse optimal design of composite structures to achieve a specified reliability level is proposed, and the corresponding maximum load is outlined as a function of ply angle. Using the generated UDM design points as input/output patterns, an Artificial Neural Network (ANN) is developed based on an evolutionary learning process. Then, a Monte Carlo simulation using ANN development is performed to simulate the behavior of the critical Tsai number, structural reliability index, and their relative sensitivities as a function of the ply angle of laminates. The results are generated for uniformly distributed random variables on a domain centered on mean values. The statistical analysis of the results enables the study of the variability of the reliability index and its sensitivity relative to the ply angle. Numerical examples showing the utility of the approach for robust design of angle-ply laminates are presented
Uncertainty assessment approach for composite structures based on global sensitivity indices
The problem of uncertainty propagation in composite laminate structures is studied. An approach based on the optimal design of composite structures to achieve a target reliability level is proposed. Using the Uniform Design Method (UDM), a set of design points is generated over a design domain centred at mean values of random variables, aimed at studying the space variability. The most critical Tsai number, the structural reliability index and the sensitivities are obtained for each UDM design point, using the maximum load obtained from optimal design search. Using the UDM design points as input/output patterns, an Artificial Neural Network (ANN) is developed based on supervised evolutionary learning. Finally, using the developed ANN a Monte Carlo simulation procedure is implemented and the variability of the structural response based on global sensitivity analysis (GSA) is studied. The GSA is based on the first order Sobol indices and relative sensitivities. An appropriate GSA algorithm aiming to obtain Sobol indices is proposed. The most important sources of uncertainty are identified
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