275 research outputs found
Seismicity Pattern Changes before the M = 4.8 Aeolian Archipelago (Italy) Earthquake of August 16, 2010
We investigated the seismicity patterns associated with an earthquake recorded in the Aeolian Archipelago on 16, August, 2010, by means of the region-time-length (RTL) algorithm. This earthquake triggered landslides at Lipari; a rock fall on the flanks of the Vulcano, Lipari, and Salina islands, and some damages to the village of Lipari. The RTL algorithm is widely used for investigating precursory seismicity changes before large and moderate earthquakes. We examined both the spatial and temporal characteristics of seismicity changes in the Aeolian Archipelago region before the earthquake. The results obtained reveal 6-7 months of seismic quiescence which started about 15 months before the earthquake. The spatial distribution shows an extensive area characterized by seismic quiescence that suggests a relationship between quiescence and the Aeolian Archipelago regional tectonics
ka band phase locked loop oscillator dielectric resonator oscillator for satellite ehf band receiver
This paper describes the design and fabrication of a Ka Band PLL DRO having a fundamental oscillation frequency of 19.250 GHz, used as local oscillator in the low-noise block of a down converter (LNB) for an EHF band receiver. Apposite circuital models have been created to describe the behaviour of the dielectric resonator and of the active component used in the oscillator core. The DRO characterization and measurements have shown very good agreement with simulation results. A good phase noise performance is obtained by using a very highQdielectric resonator
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
In-depth analysis of single-diode model parameters from manufacturer’s datasheet
The objective of this paper is to determine all the possible combinations of the five parameters of the
single-diode model (SDM) of a photovoltaic panel when only the following three important points
(remarkable points) of a IeV curve, namely, short circuit, maximum power and open circuit points, are
available, usually from manufacturer’s datasheet. In this work, four of the five parameters of the SDM are
expressed as explicit functions of the remaining one. Taking advantage of this, the monotony of these
functions has been studied and the intervals where the corresponding parameters belong have been
determined, that is, the domain of the parameters, in terms exclusively of the remarkable points. Using
these functions, a unique SDM solution can be also easily determined if an extra data or equation is
available. A possible application of this study is to validate if an extra equation is compatible with the set
of equations obtained from the remarkable points. The results presented in this paper have been tested
with a database gathering information of 8835 datasheets included in the Energy Commission’s Solar
Equipment Lists. Comparisons have also been made with other works which have tried to obtain the
SDM parameters only with datasheet information
Efficient Method for the Computation of Lightning Current Distributions in Wind Turbine Blades using the Fourier Transform and the Finite Element Method
Rotor blades of large, modern wind turbines are susceptible to lightning strikes. In order to produce a design that resists lightning strikes, it is crucial to simulate lightning current propagation in the blade components. Since the current in the blade is generated by the superposition of potential and induced electric fields, a coupling exists between electric and magnetic fields which need to be calculated by an imposed integral constraint at each time step. Commercial software packages can deal with such constraints, but it results in time-consuming computations. Therefore, this work aims to develop a numerical methodology able to compute the voltage which drives the lightning current through the structure. In this way, the problem is reformulated as a voltage-driven one which in turn allows a simple subsequent coupling of electrical and magnetic problems. The computation of the voltage waveform was accomplished using the fast Fourier transform and the finite element method (FEM) to compute the structure impedance in the frequency domain. The developed procedure showed high efficiency for a blade subjected to different lightning impulses. It allows a description of the time-dependent lightning current to be given, as well as the distribution of current within the blade conductors
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
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
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
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