225 research outputs found
Efficiency Optimization in Medium Power Wind Turbines: an Innovative Mechanical Pitch Control System
The paper illustrates the design of a new mechanical system for propeller blades pitch calibration in medium power wind turbines. The peculiarity of this system is its capacity of adjusting through a feedback control system, which allows the wind turbine to capture the maximum amount of energy from the wind. In this work an axial drive system was studied by means of racks capable of linearly adjusting the pitch of all wind turbine propeller blades in an intrinsically synchronous way, with an advantage over the traditional methods of propeller blades pitch calibration. For different wind speeds the system adjusts the blades angle of incidence in order to reduce the rotation speed and keep the system as close as possible to the pre-established design conditions generating maximum energy with a high efficiency. The manuscript examines the main analyses and simulations conducted during the design phase. These show that the proposed method allows to reach higher efficiencies with a greater intrinsic stability compared to the traditional pitch control mechanisms in medium power wind turbines. The experimental results on the first prototypes confirm the efficiency increase
Progettazione ed installazione di tre telecamere di sorveglianza per il monitoraggio dell’attività dell’Etna nel periodo Luglio-Agosto 2001
La sorveglianza visiva dei vulcani attivi siciliani è una delle attività dell’unità funzionale monitoraggio dell’INGV di Catania e consiste nel monitoraggio video continuo di detti vulcani mediante stazioni permanenti. A seguito dell’attività dell’Etna del Luglio-Agosto 2001, la stazione video che riprendeva i crateri sommitali del vulcano, posta in località La Montagnola, è stata completamente distrutta dall'attività esplosiva ed eruttiva della nuova bocca venutasi a creare a quota 2550 m. s.l.m. a ridosso del fianco settentrionale de La Montagnola. In questo lavoro è stata rappresentata l’opera di progettazione, realizzazione ed installazione di tre stazioni video, una prossimale e due periferiche, per consentire una visione completa e continua di detta attività eruttiva.
La prima telecamera è stata installata al Centro Operativo Acquisizione Dati (CUAD) di Catania, la seconda in località Rifugio Sapienza sul tetto dell’Hotel Corsaro e la terza è stata posizionata al Comune di Milo nell'edificio comunale
INSTALLAZIONE DI UN CLINOMETRO AD ALTA PRECISIONE IN AREA TETTONICA (SETTORE NORD-ORIENTALE DELL’ALTIPIANO IBLEO)
In questo rapporto sono riportati i dettagli dell’installazione di un clinometro profondo effettuata nel 2010 in prossimità di Pedagaggi (SR) nel settore nord-orientale dell’altipiano ibleo.
L'installazione è stata possibile utilizzando uno strumento digitale autolivellante modello AGI (Applied Geomechanics Incorporated) Lily, con sensibilità pari a 0.005 microradianti.
Sono illustrati i dettagli dell’installazione ed i primi dati che evidenziano la loro ottima qualità , la presenza delle componenti mareali e la minima variazione di inclinazione ottenibile ripulendo il segnale dalle stesse
Compensation Admittance Load Flow: A Computational Tool for the Sustainability of the Electrical Grid
Compensation Admittance Load Flow (CALF) is a power flow analysis method that was developed to enhance the sustainability of the power grid. This method has been widely used in power system planning and operation, as it provides an accurate representation of the power system and its behavior under different operating conditions. By providing a more accurate representation of the power system, it can help identify potential problems and improve the overall performance of the grid. This paper proposes a new approach to the load flow (LF) problem by introducing a linear and iterative method of solving LF equations. The aim is to obtain fast results for calculating nodal voltages while maintaining high accuracy. The proposed CALF method is fast and accurate and is suitable for the iterative calculations required by large energy utilities to solve the problem of quantifying the maximum grid acceptance capacity of new energy from renewable sources and new loads, known as hosting capacity (HC) and load capacity (LC), respectively. Speed and accuracy are achieved through a properly designed linearization of the optimization problem, which introduces the concept of compensation admittance at the node. The proposed method was validated by comparing the results obtained with those coming from state-of-the-art methods
High precision tilt observation at Mt. Etna Volcano, Italy
In 2007-2008, we installed on Mt. Etna two deep tilt stations using high resolution, self-leveling
instruments. These installations are the result of accurate instrument tests, site selection, drilling and
sensor positioning that has allowed detecting variations related to the principal diurnal and
semidiurnal tides for first time on Mt. Etna using tilt data.
We analyzed the tidal effects recorded on tilt signals and we removed tidal effects from signals,
thereby allowing to detect changes of about 20 nanoradians with a considerable improvement
respect to the previous installation.
Tilt changes have accompanied the Mt. Etna main eruptive phases and are generally related to the
rapid rise of magma and formation of dikes and eruptive fissures. However, tilt changes characterize
lava fountains, earthquakes and inflation-deflation phases.
The 2008-2009 eruption represents an example of the potential of these tiltmeters providing new
perspectives for highly precise monitoring of ground deformation on volcanoes
Tilt measurements at Vulcano Island
A network of tiltmeters has been operational on Vulcano Island for numerous years. At present, the network comprises five functioning borehole stations, four of which are installed at 8-10 m and allow recording very stable, high precision signals with very low noise.
We report observations over the last 12 years that illustrate impulsive variations linked to seismicity and long-term (several years) trends in the signals. We suggest a relationship between tilt changes correlated to the strongest regional seismic events and site acceleration; long-term tilt variations analyzed in combination with other ground deformation data seem to represent the evidence of a contraction of the La Fossa cone.
We also analyzed how the tilt device has the capability to detect possible magma migrations; we considered previous studies that have imaged spatially well-defined levels of magma accumulation beneath La Fossa, and Vulcanello; we concluded that the Vulcano tilt network should be capable of detecting the upward migration of small magma volumes.
Finally, we show that no evidence of changes are visible on tilt signals during anomalous degassing episodes (linked to a building up input of magmatic fluids) at the La Fossa thereby evidencing that no magma migration occurred during such events
Spin-Hall nano-oscillator with oblique magnetization and Dzyaloshinskii-Moriya interaction as generator of skyrmions and nonreciprocal spin-waves
Spin-Hall oscillators are promising sources of spin-wave signals for
magnonics applications, and can serve as building blocks for magnonic logic in
ultralow power computation devices. Here, we analytically and micromagnetically
study magnetization dynamics excited in a Spin-Hall oscillator with oblique
magnetization when the spin-Hall effect and interfacial Dzyaloshinskii-Moriya
interaction act simultaneously. Our key results are (i) excitation of
nonreciprocal spin-waves propagating perpendicularly to the in-plane projection
of the static magnetization, (ii) skyrmions generation by pure spin-current,
(iii) excitation of a new spin-wave mode with a spiral spatial profile
originating from a gyrotropic rotation of a dynamical skyrmion. These results
demonstrate that Spin-Hall oscillators can be used as generators of magnetic
skyrmions and different types of propagating spin-waves for magnetic data
storage and signal processing applications
Scalable synchronization of spin-Hall oscillators in out-of-plane field
A strategy for a scalable synchronization of an array of spin-Hall
oscillators (SHOs) is illustrated. In detail, we present micromagnetic
simulations of two and five SHOs realized by means of couples of triangular
golden contacts on the top of a Pt/CoFeB/Ta trilayer. Results highlight that
the synchronization occurs for the whole current region that gives rise to the
excitation of self-oscillations. This is linked to the role of the
magnetodipolar coupling, which is the phenomenon driving the synchronization
when the distance between oscillators is not too large. Synchronization turns
out to be also robust against geometrical differences of the contacts,
simulated by considering variable distances between the tips ranging from 100nm
to 200nm. Besides, it entails an enlargement of the radiation pattern that can
be useful for the generation of spin-waves in magnonics applications.
Simulations performed to study the effect of the interfacial
Dzyaloshinskii-Moriya interaction show nonreciprocity in spatial propagation of
the synchronized spin-wave. The simplicity of the geometry and the robustness
of the achieved synchronization make this design of array of SHOs scalable for
a larger number of synchronized oscillators
Effects of early whole-body vibration treatment on knee neuromuscular function and postural control after anterior cruciate ligament reconstruction: A randomized controlled trial
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