Search

Bearing in mind the destructive potential of tsunamis induced by volcanic landslides, the tsunamigenic event occurring at Stromboli volcano in Italy on 30 December 2002 has been re-examined here, by means of visible images and slope stability analysis. This was one of the few examples in the world of a flank collapse occurring at a volcano that was directly observed. We present the results of stability analyses, together with a sequence of photos collected from a helicopter a few minutes before the collapse. The result of this study is that the sequence of landslides triggering the 2002 Stromboli tsunami can be defined as the final stage of a lateral magma intrusion that exerted a high thrust at high altitude, destabilizing the entire slope. This study allows a more complete understanding of the event that took place on Stromboli on 30 December 2002. Furthermore, the approach used here, if appropriately modified, can be used in other contexts, contributing to the understanding of the condition that leads to tsunamigenic landslides.

A closed form, high-frequency solution is presented for the field radiated by an electric dipole located upon a rectangular, ground- ed dielectric slab. This solution, which is based on a physical optics formulation, is given in terms of the geometrical optics field plus ray-diffracted field contributions from the four edges. These ray-diffracted fields are decomposed into space waves, surface waves and leaky waves contributions. By superimposing the effects of elementary dipoles, the radiation of a current distribution is obtained, that simulates the effects of a patch radiating on a finite grounded substrate. Also, a closed-form solution is derived in the case when the current distribution exhibits an analytical expression of its Fourier transform. Comparisons with measurements are presented to validate the asymptotic solution.

Author(s): Capolino, F; Bussotti, P; Borselli, L; Albani, M; Maci, S | Abstract: The problem of edge diffraction close to a point caustic is analyzed in a typical dual-reflector Gregorian antenna in offset configuration. The diffraction phenomenon is produced by a perfectly conducting fin located between the feeder and the main reflector. This fin is sometimes used to reduce the coupling between the primary feed and the main reflector. For the sake of simplicity, the two-dimensional case is studied here, but the present technique can also be applied to practical three-dimensional configurations. © 1997 John Wiley a Sons, Inc.

A uniform high-frequency solution is presented for the diffraction of a horizontal electric dipole located upon a truncated, semi-infinite grounded dielectric slab. This solution is achieved by an asymptotic evaluation of a diffraction Sommerfeld-type integral, which is derived by using a physical optics formulation. The final uniform result is given in terms of a geometrical optics contribution and ray-diffracted contributions from space waves, surface waves, and leaky waves. Although this asymptotic expression is derived by assuming a large distance between the source and the edge, comparisons with a numerical integration have shown very good accuracy also for a distance about 0.2 wavelength. This solution provides physical insight into the diffraction phenomenon and an effective tool for predicting the effects of finite substrates in patch antennas. Indeed, within the expected limitations of the PO approximation, the present formulation is applicable to most of the substrate thicknesses and dielectric constants of practical interest in patch antennas.

In Italy, rainfall-induced slope failures occur every year, claiming lives and causing severe economic damage. We have designed and implemented a landslide warning system, named SANF (an acronym for national early warning system for rainfall-induced landslides), to forecast the possible occurrence of rainfall-induced landslides in Italy. The system is based on: (i) rainfall thresholds for pos- sible landslide occurrence, (ii) sub-hourly rainfall measurements obtained by a national network of 1950 rain gauges, and (iii) quantitative rainfall forecasts. Twice a day, the system compares the measured and the forecasted rainfall amounts against pre-defined ID thresholds, and assigns to each rain gauge a prob- ability of landslide occurrence. This information is used to prepare synoptic-scale maps showing where rainfall-induced landslides are expected in the next 24 hours.

A simplified model is suggested for describing aperture-coupled patch antennas in CAD applications. The scattering parameters of the antenna are calculated by assuming a single mode distribution for the currents on the slot and on the microstrip-line. The coupling between the slot and the patch is represented by superimposing a contribution from a fundamental mode and that from higher order modes. The former is described by a complex eigenvalue of a cavity model with impedance walls. The latter is described by a parallel plate waveguide model, which properly accounts for the storage of reactive energy close to the slot. Numerical results are presented and compared with experiments. In particular, S-band patches have been fabricated and tested to demonstrate the accuracy of the model. © 1993 John Wiley & Sons, Inc.

Daily runoff from 27 plots (5 m × 2 m) recorded during two rainy seasons in the Tigray highlands (Ethiopia) were analysed together with daily rainfall to calculate runoff curve numbers for hillslopes covered by semi-natural vegetation in varying stages of vegetation restoration. Curve number model parameters were derived using a least squares fitting procedure on the collected rainfall-runoff datasets. Curve numbers varied from 29 to 97. Land use type was an important explanatory factor for the variation in curve numbers, whereas hydrologic soil group was not. Curve numbers were negatively correlated with vegetation cover. Taking into account antecedent soil moisture conditions did not improve runoff prediction using the curve number method. As runoff prediction was less accurate in areas with low curve numbers, two separate regression functions relating curve numbers with vegetation cover were proposed for different land use types.

An eriended TLM technique is presenied that allows ihe use of a commercial, microwave circuit CAD software for designing the feedtng network of reciangular paich arrays. The meihod is aimed to improve ihe accuracy of the simple TLM to the level required for CAD purposes, ezpecially focusing on ihe hmrtairon io thin su bstraies.

Scattering from finite periodic structures on an infinite dielectric slab is relevant to a variety of engineering applications. Recent studies have demonstrated the effectiveness and physical insight gained when describing the scattering phenomena in terms of truncated Floquet waves (FW) and Floquet-modulated wave types. The array Green's function of a finite array may be represented collectively as the radiation from a superposition of continuous truncated FW (TFW) distributions on the aperture of the array. Since the FW series exhibits excellent convergence properties when the observation point is far away from the array surface, the TFW representation is found more efficient than the direct summation of the spatial contributions from each element of the array, especially when each FW aperture distribution is treated asymptotically. In this paper, we explore the high-frequency diffraction phenomena from a finite array of electric line sources on a truncated dielectric slab. The FW-diffracted rays and the excitation of guided waves at the array truncation are described. The effects of the slab truncation are introduced using a physical optics (PO) approximation for both the volumetric polarization currents and the ground plane surface currents. Furthermore, the diffraction mechanisms at a slab truncation of all wave types excited at the array edge are discussed. In order to validate the asymptotic formulation a full wave solution of the problem has been developed by solving an appropriate integral equation with the method of moments (MoM).

The radiation pattern of patch antennas may considerably be affected by the finiteness of the substrate, especially when surface waves are strongly excited. In particular, the correct prediction of the diffraction contributions from the edges of the finite substrate is relevant when the patches are printed on free standing structures, in which the front-to-back ratio has to be maximized. A high-frequency solution is presented for the field radiated by a patch current distribution located upon a rectangular, grounded dielectric slab. The typical values of thickness and dielectric constant used in patch antennas suggest the effective use of a physical optics (PO) approximation, which consists of estimating the radiating equivalent currents distributed on the surface and in the volume of the entire finite slab, like those induced by the source in the infinite structure. The technique developed by Borselli, Maci and Rossi (see MMET '94, Kharkov, Ukraine, 1994) is applied to find the radiation of a patch on a finite substrate. By using a proper GTD ray tracing, the canonical solution is applied to the case of a dipole on a finite, rectangular grounded slab. Next, by integrating the contributions of each element of a current distribution, the radiation of a patch on a finite substrate is modeled.

Convenient solutions are proposed and tested for new types of high-gain planar arrays. The basic configurations make use of simple radiating elements (such as printed dipoles or slots) whose gain is enhanced by a proper resonant-type double-layer structure. It is shown that a wide element spacing is possible, thus minimizing the undesirable coupling effects and reducing the problems of physical space for the feeding network. It is seen that the radiation presents many desirable features, such as a rather simplified design, a high-directivity pencil beam even with few linear elements, and low grating lobes.

A method is presented for the design and the analysis of a dielectric elliptical lens antenna slot fed by a microstrip. The elliptical shape of the lens gives a focusing property provided that the eccentricity is properly related to the dielectric constant. In particular, under this condition, all the rays outgoing from the source are refracted in the boresight direction, thus providing the focusing phenomenon. On the other hand the lens interface gives rise to reflections. Indeed, the geometrical properties of the lens itself are such that all the doubly reflected rays launched by a focal source return in phase at the original focus. In view of this property, the availability of tools for the accurate prediction of the input impedance of the antenna including multiple reflections effects is particularly important owing to the limited tuning possibilities intrinsic with integrated technology. Regarding the feed arrangement, we propose the same as that typically used in patch antennas, namely a slot which is excited by a microstrip printed on a back substrate. This structure presents several advantages, primarily due to the physical separation between the radiating elements and the feeding network. Furthermore, with respect to the alternative slot feed arrangement involving coplanar waveguides (CPW) the present solution provides radiation pattern regularity and polarization purity, which are important features in quasi-optical receiver front-ends.

The description of diffraction mechanisms at edges in a grounded dielectric slab is important in several engineering applications. The need for taking into account such effects may arise when considering actual patch antennas on finite substrates where these mechanisms may considerably affect the radiation pattern and have an influence on the directivity especially when surface waves are strongly excited. A formulation is suggested which allows for a dramatic reduction of the unknown quantity. The geometry which is treated consists on a grounded dielectric slab truncated on one side in both the dielectric and the ground plane, which is illuminated by an infinite line source placed at the substrate-air interface. By invoking the equivalence principle, the total space is separated (through an infinite surface in free-space) into into sub-regions in which the field can be calculated by standard Green's functions. After that, the solution is obtained by solving via an ordinary method of moments (MoM) scheme the integral equations that represents the continuity of the tangential electric field through the surface which divides the regions. Due to the infiniteness of this surfaces, entire domain basis functions are used. The shape of them is chosen according to the behavior of the field diffracted at the edge, which consists in contributions coming from space field, surface waves, and leaky waves excitations.

Several studies have been carried out on frequency- and time-domain scattering from finite periodic or quasi-periodic structures in free-space and on an infinite dielectric slab. These studies have demonstrated the effectiveness of describing the scattering phenomena in terms of truncated Floquet waves (FWs) and/or Floquet-modulated other wave types. By using the Poisson summation formula, the Green's function of a finite array is represented collectively as the radiation from a superposition of continuous truncated FW distributions on the aperture of the array. Since the FW series exhibits excellent convergence properties when the observation point is located away from the array surface, the above representation is found more efficient than the direct summation of the spatial contributions from each element of the array, especially when each FW aperture distribution is treated asymptotically. An investigation in terms of truncated FWs of periodic and quasiperiodic arrays of metallic filaments on a dielectric slab have been carried out by Carin et al. (1996). This study was oriented for an observable based parametrization of the Floquet mode-leaky mode interaction, and did not require a fully uniform asymptotic treatment when the observation point is located at grazing and/or close to the array edge. Here, a uniform asymptotic formulation is proposed for the same problem, that allows to predict the field radiated by the array also at a distance from the edge comparable with a half-wavelength. A grounded-slab is considered as a supporting structure to render the formulation suitable for patch antennas.

A configuration of a slotted patch antenna is introduced, which allows two or more separate operating frequencies. Both of them are associated with a radiating mode almost identical to that of a standard patch. The two resonances are related to the patch width and the slot/patch length respectively.

A new configuration of patch antenna is introduced, which provides a dual-band operation. This structure consists of an S-band cross patch with four square patches printed in the empty spaces among the arms of the cross. These patches provide a subarray working at X-band. This structure is simple to design and offers the advantage that it can be printed on a single-layer. An array geometry designed by using the above structure, is suggested. This can be suitable for satisfying the requirements of a typical dual-frequency SAR antenna.

An efficient method is presented for prediction of the input impedance of integrated elliptical lens antennas, excited by a focal radiator which consists of either a resonant slot or a slot-coupled patch. Simple equivalent networks are derived from this method which accounts for effects of multiple reflections inside the lens, which is useful for CAD purposes. Numerical results are presented to validate the equivalent networks. Furthermore, it is shown that these internal reflections significantly affect the input impedance of the primary source.

The properties of a monopole antenna on a circular, dielectric-loaded ground plane are analysed by using the finite-difference time-domain (FDTD) technique. The thickness of the dielectric slab has been chosen to maximise the decay of the space-wave contribution at grazing, thus reducing the space-wave diffraction at the truncation. This permits realisation of a low-side/back-lobe antenna provided that the spurious diffraction of the dominant TM surface wave is properly blocked. The radiation pattern of the antenna is similar to that of a monopole on an artificially soft (corrugated) disc. The accuracy of the FDTD prediction is tested by comparisons with far-field measurements and a moment-method analysis.

The Authors analyse the main body of somatotropin function test: insulin hypoglycemia; arginine; ornithine; I-dopa; clonidine; galanin; GH-RH; physical exercise; sleep; combined stimuli; spontaneous GH secretion of varying duration. The advantages and disadvantages of the different tests are pointed out and some recent contradictory findings concerning the newest prolonged techniques are reported. The Authors claim priority for the clinical/auxological examination, with measurement of bone age and growth velocity and suggest the procedure for GH deficit diagnosis to be followed, also in the light of their personal experience.

The AA. performed a study on the Bravais-Galton's correlation coefficient. They applied this coefficient to the HCAB/HCAC ratio and to the fetal haemoglobin often groups of twenty children (one month four years old) values. The result support the assumption that there is a strong biochemical relationship between zinc-carbonic anhydrase and haemoglobin in erithrocytes.

The interest of clinicians has recently turned to the study of acute phase proteins whose determination, especially in the newborn, offers not only diagnostic information, but also information about prognosis. For many years we have been interested in the study of orosomucoid behaviour in newborn term babies and in low weight premature babies. For this purpose 113 patients were tested, divided into different gestational age groups, from which samples were taken immediately after birth, on the following days and before beginning any kind of treatment to show the behaviour of acid glycoprotein until normal average values were reached. Statistical processing of the data showed an average orosomucoid value in newborn term babies in perfect agreement with the literature. There was correlation among gestational age, weight at birth and orosomucoid concentration, which peaked more quickly the greater the gestational age and weight at birth. Thereafter, the concentration decreased until it stabilised at average term newborn values.