Surprises of the transformer as a coupled oscillator system

We study a system of two RLC oscillators coupled through a variable mutual inductance. The system is interesting because it exhibits some peculiar features of coupled oscillators: (i) there are two natural frequencies; (ii) in general, the resonant frequencies do not coincide with the natural frequencies; (iii) the resonant frequencies of both oscillators differ; (iv) for certain choices of parameters, there is only one resonant frequency, instead of the two expected

Defining and Prototyping a Life-cycle for Dynamic Service Composition

Since the Internet has become a commodity in both wired and wireless environments, new applications and paradigms have emerged to explore this highly distributed and widespread system. One such paradigm is service-orientation, which enables the provision of software functionality as services, \ud allowing in this way the construction of distributed systems with loosely coupled parts. The Service-Oriented Architecture (SOA) provides a set of principles to create service-oriented systems, by defining how services can be \ud created, composed, published, discovered and invoked. In accordance with these principles, in this paper we address the challenge of performing dynamic service composition. The composition process and its associated tasks have to be precisely defined so that the different problems of dynamic service composition can be identified and tackled. To achieve this, this paper defines a life-cycle for dynamic service composition, which defines the required phases and stakeholders. Furthermore, we present our prototype in which the different phases of the dynamic service composition life-cycle are being implemented. This prototype is being used to experiment with and validate our initial ideas on dynamic service composition

Geoheritage of Portugal as the support for nature conservation and land-use planning

O inventário nacional do património geológico reúne os principais geossítios em Portugal com elevado valor científico e que representam a geodiversidade nacional, permitindo compreender a história e a evolução geológica do nosso território. O inventário, disponível na internet, é uma ferramenta obrigatória para todos aqueles que se dedicam a ações de conservação da natureza, de ordenamento do território e a estudos de impacte ambiental.The national inventory of geoheritage comprehends the main Portuguese geosites with high scientific value. These geosites represent the national geodiversity and allow the understanding of the geological evolution of the Portuguese territory. The inventory is available on-line and constitutes a fundamental tool to support nature conservation, land-use planning and environmental impact assessment actions.Trabalho integrado no projeto estratégico (PEst-OE/CTE/UI0039/2014) do Centro de Geologia da Universidade do Porto, apoiado pela Fundação para a Ciência e Tecnologia

A PORTABLE AND INEXPENSIVE DO-IT-YOURSELF TEMPERATURE SENSOR

Nowadays it is important to have commercial solutions to be used in teaching and research laboratories for the needs. We can have different equipment according to the necessary parameters of control being related to the influence of parameters internal or external to the laboratory practice. However they can't be straightforward to use, their costs can be considerable.  In this context, the do-it-yourself approach is an interesting alternative. In this paper we report the construction of a temperature sensor made by students. Based on a probe taken from a deactivated equipment, the sensor development and validation encompassed its design and building up, the establishment of a connection to a personal computer via USB, the setup of computer-controlled processes, which included remote control, graphical and numerical displaying and signal acquisition, and finally its testing. Tests were performed in water containers with different temperatures, namely boiling, room and ice. The obtained results are comparable to those from a commercial thermometer. This student experiment project allowed not only to contact different disciplines such as chemistry, electronics, and programming but also to gain competencies that can be used outside the class context. We proved it is possible to build tailor-made electronic devices capable of providing useful measurements to chemical purposes old equipment in an inexpensive and trustworthy way