Ocean Ultrasonic Shear and Compression Viscosities

[EN]A comprehensive description of ocean molecular flow and deformation is provided with the help of hydrodynamic and ultrasonic principles. Hydrodynamic computation of true or natural viscosities shows that ocean shear viscosity (?G), compression viscosity (?K), and extensional viscosity (?E) are interrelated. There are no experimental methods available for the in situ measurement of these viscosities. Sound absorption coefficients (? obs) allow to know the ultrasonic shear (?UG), compression (?UK), and longitudinal (?L) viscosities, which decrease with increasing frequency and increase with increasing temperature, the flow activation energies having nearly equivalent values; pressure (depth) increase/decrease them at low/high frequencies. The viscosities ?* UG, ?* UK, ?* L are approached at about 1000 KHz. They decrease with temperature and pressure, and increase with salinity. The ?*UG becomes equal to the true shear viscosity ? G at the viscosity ratio ? = ?UK / ?UG = 0.

Short-term variability of picoplankton across wind-shear region south of Gran Canaria

Máster en Oceanografía

Dynamics of the Gulf of California (GC). A case study of the internal waves using synthetic aperture radar (SAR)

Calificación: Matrícula de Honor

Short-term variability of picoplankton across the wind-shear region south of Gran Canaria

[EN]We have studied the short-term variability -at temporal scale of days and spatial scale of 5 km- of the hydrographic field, organic and inorganic nutrients, chlorophyll and picoplanktonic abundances, across a 40 Km section crossing a frontal system south of Gran Canaria, where anticyclonic eddies in early-stages of formation and convergent fronts have been widely reported in the past. Each cruise consisted in a 3-4 daily-repeated section, and was carried out at the same period of the year (May) during two consecutive years (2011 and 2012). The main goal of our study was to analyze the picoplankton response to short-term variability at scales not considered in regular oceanographic samplings, even in regions with complex hydrographic fields.

Shallow and deep deformation in northern Apennines region using seismological data

For its particular position and the complex geological history, the Northern Apennines has been considered as a natural laboratory to apply several kinds of investigations. By the way, it is complicated to joint all the knowledge about the Northern Apennines in a unique picture that explains the structural and geological emplacement that produced it. The main goal of this thesis is to put together all information on the deformation - in the crust and at depth - of this region and to describe a geodynamical model that takes account of it. To do so, we have analyzed the pattern of deformation in the crust and in the mantle. In both cases the deformation has been studied using always information recovered from earthquakes, although using different techniques. In particular the shallower deformation has been studied using seismic moment tensors information. For our purpose we used the methods described in Arvidsson and Ekstrom (1998) that allowing the use in the inversion of surface waves [and not only of the body waves as the Centroid Moment Tensor (Dziewonski et al., 1981) one] allow to determine seismic source parameters for earthquakes with magnitude as small as 4.0. We applied this tool in the Northern Apennines and through this activity we have built up the Italian CMT dataset (Pondrelli et al., 2006) and the pattern of seismic deformation using the Kostrov (1974) method on a regular grid of 0.25 degree cells. We obtained a map of lateral variations of the pattern of seismic deformation on different layers of depth, taking into account the fact that shallow earthquakes (within 15 km of depth) in the region occur everywhere while most of events with a deeper hypocenter (15-40 km) occur only in the outer part of the belt, on the Adriatic side. For the analysis of the deep deformation, i.e. that occurred in the mantle, we used the anisotropy information characterizing the structure below the Northern Apennines. The anisotropy is an earth properties that in the crust is due to the presence of aligned fluid filled cracks or alternating isotropic layers with different elastic properties while in the mantle the most important cause of seismic anisotropy is the lattice preferred orientation (LPO) of the mantle minerals as the olivine. This last is a highly anisotropic mineral and tends to align its fast crystallographic axes (a-axis) parallel to the astenospheric flow as a response to finite strain induced by geodynamic processes. The seismic anisotropy pattern of a region is measured utilizing the shear wave splitting phenomenon (that is the seismological analogue to optical birefringence). Here, to do so, we apply on teleseismic earthquakes recorded on stations located in the study region, the Sileny and Plomerova (1996) approach. The results are analyzed on the basis of their lateral and vertical variations to better define the earth structure beneath Northern Apennines. We find different anisotropic domains, a Tuscany and an Adria one, with a pattern of seismic anisotropy which laterally varies in a similar way respect to the seismic deformation. Moreover, beneath the Adriatic region the distribution of the splitting parameters is so complex to request an appropriate analysis. Therefore we applied on our data the code of Menke and Levin (2003) which allows to look for different models of structures with multilayer anisotropy. We obtained that the structure beneath the Po Plain is probably even more complicated than expected. On the basis of the results obtained for this thesis, added with those from previous works, we suggest that slab roll-back, which created the Apennines and opened the Tyrrhenian Sea, evolved in the north boundary of Northern Apennines in a different way from its southern part. In particular, the trench retreat developed primarily south of our study region, with an eastward roll-back. In the northern portion of the orogen, after a first stage during which the retreat was perpendicular to the trench, it became oblique with respect to the structure.

Nonlinear/electromagnetic co-simulation of microwaves and millimeter-waves links

The Ph.D. thesis describes the simulations of different microwave links from the transmitter to the receiver intermediate-frequency ports, by means of a rigorous circuit-level nonlinear analysis approach coupled with the electromagnetic characterization of the transmitter and receiver front ends. This includes a full electromagnetic computation of the radiated far field which is used to establish the connection between transmitter and receiver. Digitally modulated radio-frequency drive is treated by a modulation-oriented harmonic-balance method based on Krylov-subspace model-order reduction to allow the handling of large-size front ends. Different examples of links have been presented: an End-to-End link simulated by making use of an artificial neural network model; the latter allows a fast computation of the link itself when driven by long sequences of the order of millions of samples. In this way a meaningful evaluation of such link performance aspects as the bit error rate becomes possible at the circuit level. Subsequently, a work focused on the co-simulation an entire link including a realistic simulation of the radio channel has been presented. The channel has been characterized by means of a deterministic approach, such as Ray Tracing technique. Then, a 2x2 multiple-input multiple-output antenna link has been simulated; in this work near-field and far-field coupling between radiating elements, as well as the environment factors, has been rigorously taken into account. Finally, within the scope to simulate an entire ultra-wideband link, the transmitting side of an ultrawideband link has been designed, and an interesting Front-End co-design technique application has been setup.

Kinematic interaction factors of deep foundations with inclined piles.

[EN]The beneficial or detrimental role of battered piles on the dynamic response of piled foundations has not been yet fully elucidated. In order to shed more light on this aspect, kinematic interaction factors of deep foundations with inclined piles, are provided for single battered piles, as well as for 2X2 and 3X3 groups of piles subjected to vertically incident plane shear S waves.