3D Transition Matrix Solution for a Path Dependency Problem of Markov Chains-Based Prediction in Cellular Networks

Handover (HO) management is one of the critical challenges in current and future mobile communication systems due to new technologies being deployed at a network level, such as small and femtocells. Because of the smaller sizes of cells, users are expected to perform more frequent HOs, which can increase signaling costs and also decrease user's performance, if a HO is performed poorly. In order to address this issue, predictive HO techniques, such as Markov chains (MC), have been introduced in the literature due to their simplicity and generality. This technique, however, experiences a path dependency problem, specially when a user performs a HO to the same cell, also known as a re-visit. In this paper, the path dependency problem of this kind of predictors is tackled by introducing a new 3D transition matrix, which has an additional dimension representing the orders of HOs, instead of a conventional 2D one. Results show that the proposed algorithm outperforms the classical MC based predictors both in terms of accuracy and HO cost when re-visits are considered

Introducing a Novel Minimum Accuracy Concept for Predictive Mobility Management Schemes

In this paper, an analytical model for the minimum required accuracy for predictive methods is derived in terms of both handover (HO) delay and HO signaling cost. After that, the total HO delay and signaling costs are derived for the worst-case scenario (when the predictive process has the same performance as the conventional one), and simulations are conducted using a cellular environment to reveal the importance of the proposed minimum accuracy framework. In addition to this, three different predictors; Markov Chains, Artificial Neural Network (ANN) and an Improved ANN (IANN) are implemented and compared. The results indicate that under certain circumstances, the predictors can occasionally fall below the applicable level. Therefore, the proposed concept of minimum accuracy plays a vital role in determining this corresponding threshold

Arguments towards a humanization of science

Identificando a rutura no desenvolvimento da ciência entre o contexto de descoberta e o contexto de justificação, julgamos poder entender melhor a dominação do ensino transmissivo da ciência em contexto escolar e melhor argumentar para a sua superação. Por outro lado, o argumento que aqui defendemos para recuperar, para o contexto de sala de aula, a fortíssima chama cultural que a ciência transporta nos seus conceitos, leis e teorias, bem como no seu próprio processo de desenvolvimento, tem uma tradição enraizada na cultura portuguesa que exploramos.ABSTRACT By identifying the rupture in the development of science between the context of discovery and the context of justification, we believe can better understand the domination of transmissive teaching of science in schools and argue for overcoming it. The argument is to recover for the classroom the very strong cultural flame that science carries in its concepts, laws and theories as well as in its own developmental processes. We explore the tradition rooted in Portuguese culture

A survey of machine learning techniques applied to self organizing cellular networks

In this paper, a survey of the literature of the past fifteen years involving Machine Learning (ML) algorithms applied to self organizing cellular networks is performed. In order for future networks to overcome the current limitations and address the issues of current cellular systems, it is clear that more intelligence needs to be deployed, so that a fully autonomous and flexible network can be enabled. This paper focuses on the learning perspective of Self Organizing Networks (SON) solutions and provides, not only an overview of the most common ML techniques encountered in cellular networks, but also manages to classify each paper in terms of its learning solution, while also giving some examples. The authors also classify each paper in terms of its self-organizing use-case and discuss how each proposed solution performed. In addition, a comparison between the most commonly found ML algorithms in terms of certain SON metrics is performed and general guidelines on when to choose each ML algorithm for each SON function are proposed. Lastly, this work also provides future research directions and new paradigms that the use of more robust and intelligent algorithms, together with data gathered by operators, can bring to the cellular networks domain and fully enable the concept of SON in the near future

A utilização de betões leves em vigas mistas aço-betão

A presente comunicação descreve o conjunto de ensaios experimentais realizados no Laboratório de Estruturas de Engenharia Civil da Universidade do Minho (LEST-UM), com vista à avaliação de possibilidades e vantagens da utilização de betões leves de elevada resistência em vigas mistas aço-betão. Numa primeira fase, estudaram -se as propriedades de um betão leve de elevada resistência com maior relevância para o comportamento estrutural. De seguida, procedeu-se ao estudo do comportamento dos elementos de conexão a serem utilizados. Deste modo, realizaram -se ensaios de tipo Push-out com conectores de tipo perno de cabeça inseridos em lajes realizadas com o mesmo betão leve anteriormente estudado. Por fim, realizaram -se ensaios experimentais em vigas mistas compostas pelos elementos referidos e por um perfil metálico de tipo comercial

Caracterização experimental de um betão leve de elevada resistência

Descrevem-se, neste artigo, os ensaios experimentais de caracterização do comportamento instantâneo e diferido de um betão leve de elevada resistência, realizados no Laboratório de Estruturas de Engenharia Civil da Universidade do Minho (LEST-UM). O objectivo é produzir e caracterizar um betão leve para ser utilizado em elementos estruturais.PRAXIS XXI - Projecto de investigação Sapiens ECM/33067/99 - “Steel-concrete composite bridges : use of lightweight high performance concrete"

Experimental characterization of shear connectors for steel and concrete composite bridge decks

The aim of this communication is to show the experimental work developed at University of Minho regarding the characterization of shear connectors’ structural behaviour in lightweight concrete and to compare the obtained results with results presented by other authors. The experiments conducted made it possible to determine the load capacity and the deformation capacity of shear studs and Perfobond connectors, and to evaluate its ductility. The advantages or disadvantages related to each type of shear connector and the differences between the technological solutions needed to fabricate and assemble each device are also pointed out.University of MinhoCMM-Portuguese Steelwork AssociationECCS-European Convention for Constructional Steelwor

Estudo experimental de vigas mistas aço-betão leve

A presente comunicação descreve os ensaios experimentais de vigas mistas de aço-betão leve simplesmente apoiadas, com 4.5 m de vão. A configuração geométrica e as condições de apoio são idênticas para todas as vigas, variando a distribuição de elementos de conexão entre o perfil metálico e a laje de betão. As vigas são sujeitas a um carregamento em seis pontos.PRAXIS XXI - Projecto Sapiens ECM/33067/99 (“Steel-concrete composite bridges : use of lightweight high performance concrete")

Cyclic loadings on steel and lightweight concrete composite beams

This communication describes the experimental cyclic tests performed on steel and high strength lightweight concrete composite beams, at Universidade do Minho, Portugal. The experimental study involves tests on simply supported beams, all with the same geometrical disposition, supports and materials. Headed studs are used to provide the connection between the steel profile and the lightweight concrete slab. The parameters in study are the stud disposition and the number and range of the load cycles applied. Two types of stud disposition are chosen: one that guarantees full connection and other that guarantees partial connection. The beams are tested with a six-point loading, uniformly spaced along the beam, and the cycles are controlled by load. The main objectives are: to describe the composite beams behaviour, focused on the connection between steel and lightweight concrete; to analyse the beams load capacity and to analyse the influence of the number and range of the load cycles.(undefined

Experimental studies on shear connection between steel and lightweight concrete

This communication describes the experimental tests carried out at University of Minho to study shear connection between steel and high strength lightweight concrete (HSLWC). The test configuration follows the EC4 recommendations and repeats some dispositions referred by other authors. The experimental study involves tests on studs with diameters of 19, 22 and 25 mm, T connectors produced from laminated steel profiles and Perfobond connectors with specific geometry (Figure 1). With these tests it is possible to characterize different types of connection and evaluate load and deformation capacity.The present work was financed by the Investigation Project Sapiens ECM/33067/99 - “Steel-concrete composite bridges : use of lightweight high performance concrete”, from Program PRAXIS XXI, financed by FEDER, through POCTI