Abstract
The ability of NoSQL systems to scale better than traditional relational databases motivates a large set of applications to migrate their data to NoSQL systems, even without aiming to exploit the provided schema exibility. However, accessing structured data is costly due to such exibility, incurring in a lot of bandwidth and processing unit usage. In this paper, we analyse this cost in Apache HBase and propose a new scan operation, named Prepared Scan, that optimizes the access to data structured in a regular manner by taking advantage of a well-known schema by application. Using an industry standard benchmark, we show that Prepared Scan improves throughput up to 29% and decreases network bandwidth consumption up to 20%.

Abstract
This paper briefly proposes a technique to detect energy inefficient fragments in the source code of a software system. Test cases are executed to obtain energy consumption measurements, and a statistical method, based on spectrum-based fault localization, is introduced to relate energy consumption to the system's source code. The result of our technique is an energy ranking of source code fragments pointing developers to possible energy leaks in their code.

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The paper explores the improvement in ancillary services that variable speed technologies can provide for the case of an existing pumped storage power plant of 2x210 MVA which conversion from fixed speed to variable speed is investigated with a focus on the power step performances of the units. First two motor-generator variable speed technologies are introduced, namely the Doubly Fed Induction Machine (DFIM) and the Full Scale Frequency Converter (FSFC). Then a detailed numerical simulation model of the investigated power plant used to simulate power steps response and comprising the waterways, the pump-turbine unit, the motor-generator, the grid connection and the control systems is presented. Hydroelectric system time domain simulations are performed in order to determine the shortest response time achievable, taking into account the constraints from the maximum penstock pressure and from the rotational speed limits. It is shown that the maximum instantaneous power step response up and down depends on the hydro-mechanical characteristics of the pump-turbine unit and of the motor-generator speed limits. As a results, for the investigated test case, the FSFC solution offer the best power step response performances.

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The original version of this article unfortunately contained amistake. The presentation of Table 3 was incorrect. The corrected (Table 3) is given below. © 2017, Springer Science+Business Media New York.

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O III Congresso Ibero-Americano de Empreendedorismo, Energia, Ambiente e Tecnologia (CIEEMAT), dá continuidade ao trabalho desenvolvido no Brasil pelo Centro Federal de Educação Tecnológica Celso Suckow da Fonseca – Rio de Janeiro, atravessando o oceano Atlântico para a sua primeira edição no contexto da Península Ibérica. Concebido para englobar um conjunto abrangente de áreas temáticas, este evento serve de ponto de encontro entre profissionais, investigadores, professores e estudantes dos países Ibero-Americanos, num fórum que reforça o perfil internacional do Instituto Politécnico de Bragança, assim como das demais Instituições Organizadoras e Parceiras, designadamente, no âmbito de Programas de Dupla Diplomação. Nos três dias do evento, esperamos que encontrem oportunidades para a partilha de ideias e resultados de investigação, reforçando ou estabelecendo novos contactos e parcerias no espaço Latino-Americano. Por fim, espero que a Vossa estadia em Bragança seja agradável e que levem de volta gratas recordações do CIEEMAT 2017.