Detection, Location and Imaging of Multiple Scatterers by means of the Iterative Multiscaling Method

In this paper, a new version of the iterative multiscaling method (IMM) is proposed for reconstructing multiple scatterers in two-dimensional microwave imaging problems. The manuscript describes the new procedure evaluating the effectiveness of the IMM previously assessed for single object detection. Starting from inverse scattering integral equations, the problem is recast in a minimization one by defining iteratively (at each level of the scaling procedure) a suitable cost function allowing firstly a detection of the unknown objects, successively a location of the scatterers and finally a quantitative reconstruction of the scenario under test. Thanks to its properties, the approach allows an effective use of the information achievable from inverse scattering data. Morover, the adopted kind of expansion is able to deal with all possible multiresolution combinations in an easy and computationally inexpensive way. Selected numerical examples concerning dielectric as well as dissipative objects in noisy enviroments or starting from experimantally-acquired data are reported in order to confirm the usefulness of the introduced tool and of the effectiveness of the proposed procedure

I would walk 500 miles (if it paid)

One of the pillars of the educational voucher system instituted in Chile is that competition among schools to attract students would improve the quality of the education provided. Surveys have suggested that families rank the distance of the school from their home as the most important factor for choosing a school. They also suggest that parents largely ignore the results of standardized tests. We use a novel data set which includes measures of the distance between homes and schools to analyze the determinants of school choice. Economic theory suggests, and the estimations confirm, that parents consider quality of the school and its location when choosing schools. The paper quantifies the relevant trade-offs.Vouchers; School Choice; Distance; Chile

Mathematical Methods for 4d N=2 QFTs

In this work we study different aspects of 4d N = 2 superconformal field theories. Not only we accurately define what we mean by a 4d N = 2 superconformal field theory, but we also invent and apply new mathematical methods to classify these theories and to study their physical content. Therefore, although the origin of the subject is physical, our methods and approach are rigorous mathematical theorems: the physical picture is useful to guide the intuition, but the full mathematical rigor is needed to get deep and precise results. No familiarity with the physical concept of Supersymmetry (SUSY) is need to understand the content of this thesis: everything will be explained in due time. The reader shall keep in mind that the driving force of this whole work are the consequences of SUSY at a mathematical level. Indeed, as it will be detailed in part II, a mathematician can understand a 4d N = 2 superconformal field theory as a complexified algebraic integrable system. The geometric properties are very constrained: we deal with special K\ua8ahler geometries with a few other additional structures (see part II for details). Thanks to the rigidity of these structures, we can compute explicitly many interesing quantities: in the end, we are able to give a coarse classification of the space of "action" variables of the integrable system, as well as a fine classification -- only in the case of rank k = 1 -- of the spaces of "angle" variables. We were able to classify conical special K\ua8ahler geometries via a number of deep facts of algebraic number theory, diophantine geometry and class field theory: the perfect overlap between mathematical theorems and physical intuition was astonishing. And we believe we have only scratched the surface of a much deeper theory: we can probably hope to get much more information than what we already discovered; of course, a deeper study of the subject -- as well as its generalizations -- is required. A 4d N = 2 superconformal field theory can thus be defined by its geometric structure: its scaling dimensions, its singular fibers, the monodromy around them and so on. But giving a proper and detailed definition is only the beginning: one may be interested in exploring its physical content. In particular, we are interested in supersymmetric quantities such as BPS states, framed BPS states and UV line operators. These quantities, thanks to SUSY, can be computed independently of many parameters of the theory: this peculiarity makes it possible to use the language of category theory to analyze the aforementioned aspects. As it will be proven in part V, to each 4d N = 2 superconformal field theory we can associate a web of categories, all connected by functors, that describe the BPS states, the framed BPS states (IR) and the UV line operators. Hence, following the old ideas of \u2018t Hooft, it is possible to describe the phase space of gauge theories via categories, since the vacuum expectation values of such line operators are the order parameters of the confinement/deconfinement phase transitions. Mathematically, the (quantum) cluster algebra of Fomin and Zelevinski is the structure needed. Moreover, the analysis of BPS objects led us to a deep understanding of generalized S-dualities. Not only were we able to precisely define -- abstractly and generally -- what the S-duality group of a 4d N = 2 superconformal field theory should be, but we were also able to write a computer algorithm to obtain these groups in many examples (with very high accuracy)

Detection of Buried Inhomogeneous Elliptic Cylinders by a Memetic Algorithm

The application of a global optimization procedure to the detection of buried inhomogeneities is studied in the present paper. The object inhomogeneities are schematized as multilayer infinite dielectric cylinders with elliptic cross sections. An efficient recursive analytical procedure is used for the forward scattering computation. A functional is constructed in which the field is expressed in series solution of Mathieu functions. Starting by the input scattered data, the iterative minimization of the functional is performed by a new optimization method called memetic algorithm. (c) 2003 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works

A Reconstruction Procedure for Microwave Nondestructive Evaluation based on a Numerically Computed Green's Function

This paper describes a new microwave diagnostic tool for nondestructive evaluation. The approach, developed in the spatial domain, is based on the numerical computation of the inhomogeneous Green’s function in order to fully exploit all the available a-priori information of the domain under test. The heavy reduction of the computational complexity of the proposed procedure (with respect to standard procedures based on the free-space Green’s function) is also achieved by means of a customized hybrid-coded genetic algorithm. In order to assess the effectiveness of the method, the results of several simulations are presented and discussed

Ensaios sobre Strawson

Tradução para o português do livro "Ensaios sobre Strawson", de Carlos Caorsi. Editora da unijuí, 2014. Sumário: Apresentação; A teoria da verdade em Strawson, Mauricio Beuchot; Réplica a Mauricio Beuchot, Peter F. Strawson; Strawson: entre a lógica tradicional e a lógica clássica, Robert Calabria; Réplica a Robert Clabria, Peter F. Strawson; Referência e termos singulares, Carlos E. Caorsi; Réplica a Carlos E. Caorsi, Peter F. Strawson; Strawson e a metafísica, Juan C. D’Alessio; Réplica a Juan C. D’Alessio, Peter F. Strawson; A meta-metafísica de Strawson: identificação versus individuação, Jorge J. E. Gracia; Réplica a Jorge J. E. Gracia, Peter F. Strawson; Algumas distinções sobre a noção de indivíduo, Jesús Mosterín; Réplica a Jesús Mosterín, Peter F. Strawson; Sobre a percepção e seus objetos em Strawson, Ernest Sosa; Réplica a Ernest Sosa, Peter F. Strawson; Limitações ao exercício da perplexidade, Teresa de Jesús Zavalía; Réplica a Tereza de Jesús Zavalía, Peter F. Strawson; Publicações de P. F. Strawso

A Numerical Technique for Determining the Internal Field in Biological Bodies Exposed to Electromagnetic Fields

In this paper, the field prediction inside biological bodies exposed to electromagnetic incident waves is addressed by considering inverse scattering techniques. In particular, the aim is to evaluate the possibility of limiting the test area in order to strongly reduce the computational time, ensuring, at the same time, a quite accurate solution. The approach is based on separating the scattering contributions of the region under test and the other part of the biological body. The starting point is represented by the inverse-scattering equations, which are recast as a functional to be minimized. A Green's function approach is then developed in order to include an approximate knowledge (a model) of the biological body. The possible application of the approach for diagnostic purposes is also discussed

ANN-based sub-surface monitoring technique exploiting electromagnetic features extracted by GPR signals

Abstract. In this work we consider the problem of determining the dielectric characteristics of sub-surface layers by means of GPR systems. In particular, a suitable electromagnetic feature (the RΓ parameter), strictly related to the geophysical parameters of the scenario, is first extracted from the GPR e.m. signal and then fed to an artificial neural network (ANN) in order to derive the dielectric permittivity of the sub-surface layer

Geometric classification of 4d N= 2 SCFTs

The classification of 4d N= 2 SCFTs boils down to the classification of conical special geometries with closed Reeb orbits (CSG). Under mild assumptions, one shows that the underlying complex space of a CSG is (birational to) an affine cone over a simply-connected \u211a-factorial log-Fano variety with Hodge numbers h p,q = \u3b4 p,q . With some plausible restrictions, this means that the Coulomb branch chiral ring [InlineMediaObject not available: see fulltext.] is a graded polynomial ring generated by global holomorphic functions u i of dimension \u394 i . The coarse-grained classification of the CSG consists in listing the (finitely many) dimension k-tuples \u394 1 , \u394 2 , ef , \u394 k which are realized as Coulomb branch dimensions of some rank-k CSG: this is the problem we address in this paper. Our sheaf-theoretical analysis leads to an Universal Dimension Formula for the possible \u394 1 , ef , \u394 k \u2019s. For Lagrangian SCFTs the Universal Formula reduces to the fundamental theorem of Springer Theory. The number N(k) of dimensions allowed in rank k is given by a certain sum of the Erd\uf6s-Bateman Number-Theoretic function (sequence A070243 in OEIS) so that for large kN(k)=2\u3b6(2)\u3b6(3)\u3b6(6)k2+o(k2). In the special case k = 2 our dimension formula reproduces a recent result by Argyres et al. Class Field Theory implies a subtlety: certain dimension k-tuples \u394 1 , ef , \u394 k are consistent only if supplemented by additional selection rules on the electro-magnetic charges, that is, for a SCFT with these Coulomb dimensions not all charges/fluxes consistent with Dirac quantization are permitted. Since the arguments tend to be abstract, we illustrate the various aspects with several concrete examples and perform a number of explicit checks. We include detailed tables of dimensions for the first few k\u2019s