Search results for "33"
showing 10 items of 1917 documents
Time and heat for sexual reproduction: comparing the phenology of Chara hispida of two populations at different latitudes
2017
Abstract Geographical location affects the main ecological factors driving the timing of plants’ life events. In addition, studying phenology is the simplest procedure to track current global warming and its effects on the success and survival of different populations of the same species. Little is known about the effect of water temperature and its corresponding accumulated heat on charophytes’ phenology. We compared differences in water temperature and sexual reproductive phenology of Chara hispida in two ponds of two countries located at different latitudes (Spain and Switzerland) over the same year. We estimated the accumulated heat required to develop from one phenophase to another (un…
Le Printemps arabe contre le terrorisme: enjeux et perspectives
2012
Cet article s'interroge sur la nature des relations susceptibles d'exister entre le Printemps arabe en tant que mouvement politique et la place du terrorisme dans l'espace musulman. Il s'interroge sur la double acception posée en termes antithétiques : A savoir le fait que le réveil des peuples de Tunis jusqu'à Benghazi en passant par Le Caire marginaliserait le terrorisme dans la mesure ou la soif de démocratie et d'égalité apparaîtrait sonner le glas de toute forme de violence politique a fortiori celle importée d'Al-Qaida ; ou bien au contraire que le déploiement de la contestation par la rue aboutissant à la fin de régimes autoritaires militaires ouvrirait la voie à l'extension d'un ter…
Experimentation of sustainable energy microsystems: The DE.DU.ENER.T. research project
2015
The paper focuses on an energy sustainable prototype micro-system installed upon a roof of a building in Valderice (Italy). This micro-system has been conceived in the ENPI (European Neighborhood and Partnership Instrument) cross-border cooperation Italy - Tunisia 2007–2013 DE.DU.ENER.T. (Le DEveloppement DUrable dans la production ENERgetique dans le Territoire) research project framework. The main aim of this project is the construction of a sustainable energy micro-system prototype suitable for the optimal integration and management of renewable energy resources (photovoltaic, wind and solar thermal) and to reduce the building's energy consumption. In the paper the project and the protot…
Transparency in transactive energy at distribution level
2017
A recent report from the German Energy Agency analyzes the possible introduction of the blockchain technology in energy transactions in power distribution. The issue deserves attention since the extensive digitalization of business models puts new challenges to utilities in the power sector. The German decision makers in the energy field claim that blockchain appears as a close perspective and, at the same time, the Gartner hypecycle puts this technology at the peak of inflated expectations in 2016. Diffuse perception however provides hints for further investigation on the topic. This paper provides insight into the problem of peer-to-peer energy exchange from a technical perspective, provi…
Distributed optimal power flow for islanded microgrids: An application to the Smart Polygeneration Microgrid of the Genoa University
2016
In this work, the application of an original distributed optimal power flow method to test a microgrid in the Savona area, Italy is proposed. The microgrid shows different types of Distributed Energy Resources (DERs) and is connected to the main grid through a fixed power bus. Due to the high computational speed, the applied distributed Optimal Power Flow can be performed almost in real time, i.e. every 5 minutes or less. The operating solution found for generators, simply using local information, corresponds to a suboptimal condition with reduced losses, bus voltages and line currents within constrained intervals. The distributed optimization algorithm is iterative, but also fast. It is ba…
Effect of voltage deviations on power distribution losses in presence of DG technology
2015
Integration of distributed generation (DG) units in power distribution network has become increasingly attractive multi-faceted paradigm as economic and environmental factors drive new technologies to be more efficient and less polluting than their earlier counterparts. The installation of DGs impacts critically on the planning and operating characteristics of the distribution network. Type, location, number and capacity of DG are essential factors for studying the effect of DGs on the system behavior. In this paper the effect of DG on the power losses of a distribution network is investigated for different types of DG units. Also, the impact of DG on the voltage profile is demonstrated bef…
Verifying the effect of distributed generators on voltage profile, power losses and protection system in radial distribution networks
2013
In the recent years the electrical power networks are undergoing rapid restructuring and developing process worldwide. Advancement in technologies and concern about the environmental impacts have led to increase interconnection of renewable energy based distributed generations (DGs) in distribution networks. The DGs have significant impacts on the distribution systems; these impacts may be either positively or negatively depending on the modified interconnected DG distribution network structure. It will be necessary to consider many issues concerning these impacts. In this paper, an investigation of DGs impacts on voltage profile, power losses, and protection system in radial distribution n…
Kroppsbilde og slankefokus blant fysisk aktive gutter i ungdomsskolen og på videregående skole i Norge :
2016
Masteroppgave i idrettsvitenskap - Universitetet i Agder 2016 The aim of this study was to investigate body image and drive for thinness among adolescent boys, and to examine variations for these variables in age and level of physical activity. This cross-sectional study is part of “the Relevance of Physical Activity Contexts in Every-Day Life of Adolescents” (REPAC), which is a larger project. 1423 boys from secondary school (8th grade) and upper secondary school (11th grade) were included in this study, and these responded to a questionnaire that was developed to examine how different activity contexts affected adolescent boys everyday lives. Correlation analysis and one-way ANOVA tests w…
Real-Time Minimization Power Losses by Driven Primary Regulation in Islanded Microgrids
2020
Islanded microgrids are small networks that work independently from the main grid. The frequency and voltage in islanded microgrids are affected directly by the output power of distributed generators and power demand variations. In this work, a real-time driven primary regulation, which relies on optimized P-f droop coefficients, is proposed. In all operating conditions, it minimizes the power losses for islanded microgrids. The proposed configuration will allow the optimization modules to interact with each other and adjust parameters producing a suitable power sharing among generators. The methodology is tested based on a hardware-in-the-loop experimental set-up where distributed generato…
Impact of Converter-Interfaced Generation to the Frequency Response of the European Power System
2019
The increase of converter-interfaced generation (CIG) typically related to renewable energy sources is progressively causing a significant change of power systems operation. The curtailment of synchronous generation with the consequent reduction of the overall kinetic energy is one of the related issues, currently under investigation in academia and industry. The work considers the problem of overall inertia reduction from a large-scale point of view, analyzing the impact of different CIG integration levels to the frequency response of the power system of Continental Europe. The kinetic energy is evaluated for each country of the synchronous area, and the system is modified substituting con…