D'Urso M.G.,University of Cassino and Southern Lazio
Journal of Geodesy | Year: 2014
On the basis of recent analytical results we derive new formulas for computing the gravity effects of polyhedral bodies which are expressed solely as function of the coordinates of the vertices of the relevant faces. We thus prove that such formulas exhibit no singularity whenever the position of the observation point is not aligned with an edge of a face. In the opposite case, the contribution of the edge to the potential to its first-order derivative and to the diagonal entries of the second-order derivative is deemed to be zero on the basis of some claims which still require a rigorous mathematical proof. In contrast with a common statement in the literature, it is proved that only the off-diagonal entries of the second-order derivative of the potential do exhibit a noneliminable singularity when the observation point is aligned with an edge of a face. The analytical provisions on the range of validity of the derived formulas have been fully confirmed by the Matlab® program which has been coded and thoroughly tested by computing the gravity effects induced by real asteroids at arbitrarily placed observation points. © 2013 Springer-Verlag Berlin Heidelberg.
Migliore M.D.,University of Cassino and Southern Lazio
IEEE Transactions on Antennas and Propagation | Year: 2011
A technique for array diagnosis using a small number of measured data acquired by a near-field system is proposed. The technique, inspired by some recent results in the field of compressed sensing, requires the preliminary measurement of a failure-free reference array. The linear system relating the difference between the field measured using the reference array and the field radiated by the array under test, and the difference between the coefficients of the reference and of the AUT array, is solved using a proper regularization procedure. Numerical examples confirm that the technique gives satisfactory results in terms of failure detection with a reduction in the number of data of two orders of magnitudes compared to standard back-propagation technique and of one order of magnitude compared to the number of elements of the array, provided that the number of fault elements is small. This result is relevant in practical applications, since the high cost of large array diagnosis in near-field facilities is mainly caused by the time required for the data acquisition. Accordingly, the technique is particularly suitable for routine testing of arrays. © 2006 IEEE.
Lucido M.,University of Cassino and Southern Lazio
IEEE Transactions on Microwave Theory and Techniques | Year: 2012
The analysis of propagation of bound and leaky modes in single and multiple coupled microstrip lines in planarly layered media by means of Galerkin's method applied to an electric field integral-equation formulation in the spectral domain with Chebyshev polynomials basis functions weighted with the edge behavior of the unknown surface current densities on the metallic strips leads to the evaluation of improper integrals of oscillating functions with a slow asymptotic decay. In this paper, a new analytical technique for drastically speeding up the computation of such integrals is presented. First, suitable half-space contributions are pulled out of the kernels, which makes the integrands exponentially decaying functions. The integrals of the extracted contributions are then expressed as combinations of proper integrals and fast converging improper integrals by means of appropriate integration procedures in the complex plane. © 1963-2012 IEEE.
Garcea E.A.A.,University of Cassino and Southern Lazio
Quaternary International | Year: 2012
Under the Out-of-Africa scenario, various routes have been supposed for the exit of the African . Homo sapiens. The Mediterranean coast of North Africa, the Sahara, the Nile Valley, the Red Sea coast, and the Bab el Mandab could have been corridors leading out of Africa. Even though data are still too scanty, heterogeneous, and patchy to support one hypothesis against the others, scholars have tended to search for " the" route out of Africa, as if one passageway would rule out possible others. However, a single-dispersal model may not be correct as early modern humans may have found different ways to leave their native lands. If North Africa can contribute to an understanding of the adaptational dynamics of modern human peopling and their radiation towards different parts of Eurasia, other regions, such as the Horn of Africa, may be contemplated as well.This paper focuses on the events that took place in North Africa. In this region, anatomically modern humans were not always successful once they departed from Africa and moved towards the temperate, and dry, latitudes of the eastern Mediterranean basin in the Levant. Two distinct movements have been recognised within the Out-of-Africa 2 model, one occurring between c. 130 and 80 ka, the other taking place after 50 ka. The two phenomena were separated by an abrupt climatic transition that affected the south-western Mediterranean basin during the transition from MIS 5a to MIS 4, around 74 ka. As these two events exhibit very distinct features and are divided by a long time span, it seems reasonable to refer to the first event as " Out of Africa 2a" and to the second one as " Out of Africa 2b" . During the first migration out of Africa, modern humans seem to have failed in the competition for resources against Neanderthals, whereas they succeeded in their second migration. This paper examines some of the reasons of the failure of the Out-of-Africa-2a migration and, on the other hand, of the success of the Out-of-Africa-2b movement with particular attention to North Africa. © 2011 Elsevier Ltd and INQUA.
Migliore M.D.,University of Cassino and Southern Lazio
IEEE Antennas and Wireless Propagation Letters | Year: 2013
In this letter, the problem of the diagnosis of arrays from far-field data is studied using the theory of Random Partial Fourier Matrices, rigorously showing the possibility of a large reduction of data. Numerical results based on $\ell1 minimization confirm the identification of the failures from a small set of measurements. © 2002-2011 IEEE.