Abstract
Faculty of Sciences of University of Porto annually organizes the Open Days to Schools, which allow the contact of high school students with researchers from different scientific areas. By recognizing a high potential to modelling, which promotes the construction of students’ knowledge through models that recreate geological phenomena, participants contacted with some models that simulated the effect of earthquakes on soils and buildings. We tried to understand if the use of models in the dissemination of Geology helps students to build their scientific knowledge, concerning seismology contents. A seismology model evaluation scale was applied to 126 high school students from schools of northern Portugal, which participated in the activities at Open Days to Schools. The results shown that students consider that models help to clarify and to restructure their knowledge about geological phenomena, highlighting the importance of modeling in the promotion of a meaningful learning. © 2014 LNEG - Laboratório Nacional de Geologia e Energia IP.

Abstract
Several methodologies have been proposed in the last decades to improve the quality of Safety-Critical Embedded Systems (SCES) and, at the same time, keep costs and schedule compatible with project plans. In particular, approaches such as Product Line Engineering (PLE) and Model-Driven Engineering (MDE) offer an interesting solution to reduce development complexity and time to market due to their synergy and common goals. However, the current state of how MDE and PLE can be combined to enhance productivity in the domain of SCES is not clear yet. This paper presents a systematic literature review, with the purpose of obtaining the state of the art of the aproaches, methods and methodologies whose goal is the combination of PLE and MDE for the development of SCES, and to verify the existence of empirical studies that demonstrate the application of these techniques in this type of development. We drew the following conclusions from the review results: (1) The number of studies using PLE with MDE to build SCES is relatively small, but has increased gradually in recent years. (2) The approaches diverge about what is needed to build Model-driven Product Lines. (3) Most of the approaches do not consider to differentiate between hardware and software variabilities. (4) Most of the studies propose the use of UML and feature diagrams. (5) The studies present case studies implemented in different tools and most of them are free. (6) The approaches do not cover the entire development lifecycle.

Abstract
The forthcoming smart grids are comprised of integrated microgrids operating in grid-connected and isolated mode with local generation, storage and demand response (DR) programs. The proposed model is based on three successive complementary steps for power transaction in the market environment. The first step is characterized as a microgrid's internal market; the second concerns negotiations between distinct interconnected microgrids; and finally, the third refers to the actual electricity market. The proposed approach is modeled and tested using a MAS framework directed to the study of the smart grids environment, including the simulation of electricity markets. This is achieved through the integration of the proposed approach with the MASGriP (Multi-Agent Smart Grid Platform) system. © IFAC.

Abstract
This paper deals with a control concept for enhancing the stable operation of microgrid plan during the grid connected and islanding modes. The Lyapunov control theory is considered in this paper to analyze the dynamic behavior of distributed generation (DG) units during the power sharing with utility grid and loads. The compensation of instantaneous variations in the reference current components of DG units in ac-side and dc-voltage variations in dcside of the interfaced converters are considered properly in this control scheme, which is the main contribution of this work in comparison with the other potential control strategies. By utilization of the proposed control scheme, DG units can provide the continuous injection of active power from the dispersed energy sources to the local loads and/or main grid during the islanding and grid-connected modes. Furthermore, reactive power and harmonic current components of loads can be provided with a fast dynamic response in a stable operational region. Simulation results confirm the effectiveness of the proposed control strategy in the proposed microgrid plan during the dynamic and steady-state operating conditions.

Abstract
Stationary batteries are currently seen as an interesting solution to deal with the variability of the renewable energy sources. In the same way as other types of storage, e.g. pumped-hydro units, this new type of storage equipment can improve the use of Renewable Energy Sources (RES). Additionally, the stationary batteries location in the grid is not as physically constrained as other storage systems and can be optimally selected to maximize its overall benefits. This paper proposes a new methodology to represent the unique stochastic behavior of stationary batteries while integrated into an electrical power system. This methodology includes not only the technical restrictions of this type of storage system but also how its operation strategy affects its lifetime. The methodology was tested on a small test system, which is based on the IEEE-RTS 79, using sequential Monte Carlo simulation as its core to accurately reproduce the chronology of events of stationary batteries. The results of the simulation are focused on the potential impacts of these storage devices not only in terms of renewable energy used but also in the adequacy of supply.

Abstract
The ability to access and query data stored in multiple versions is an important asset for many applications, such as Web graph analysis, collaborative editing platforms, data forensics, or correlation mining. The storage and retrieval of versioned data requires a specific API and support from the storage layer. The choice of the data structures used to maintain versioned data has a fundamental impact on the performance of insertions and queries. The appropriate data structure also depends on the nature of the versioned data and the nature of the access patterns. In this paper we study the design and implementation space for providing versioning support on top of a distributed key-value store (KVS). We define an API for versioned data access supporting multiple writers and show that a plain KVS does not offer the necessary synchronization power for implementing this API. We leverage the support for listeners at the KVS level and propose a general construction for implementing arbitrary types of data structures for storing and querying versioned data. We explore the design space of versioned data storage ranging from a flat data structure to a distributed sharded index. The resulting system, ALEPH, is implemented on top of an industrial-grade open-source KVS, Infinispan. Our evaluation, based on real-world Wikipedia access logs, studies the performance of each versioning mechanisms in terms of load balancing, latency and storage overhead in the context of different access scenarios.