136 research outputs found
A characterization of the sporadic group of Lyons
No full textWe show that Lyons' sporadic simple group is the unique finite simple group that is simultaneously of weak characteristic -type and characteristic -type for odd and with and
Full-wave Validation of Plane Waves Model for Numerical Dosimetry in Reverberation Chambers
No full textA full wave method developed for the analysis of lossy dielectric disks is applied to the evaluation of the field induced in a Petri dish exposed in a reverberation chamber. The rich scattering environment can be modeled by means of a plane wave expansion, which is usually approximated taking into account only a few waves. The proposed method allows to assess the accuracy achieved for any given number of considered plane waves
Author response to: Prophylactic sublay non-absorbable mesh positioning following midline laparotomy in a clean-contaminated field: randomized clinical trial (PROMETHEUS)
No full textAnalysis of the Scattering from a Two Stacked Thin Resistive Disks Resonator by Means of the Helmholtz–Galerkin Regularizing Technique
No full textIn this paper, the scattering of a plane wave from a lossy Fabry–Perót resonator, realized with two equiaxial thin resistive disks with the same radius, is analyzed by means of the generalization of the Helmholtz–Galerkin regularizing technique recently developed by the author. The disks are modelled as 2-D planar surfaces described in terms of generalized boundary conditions. Taking advantage of the revolution symmetry, the problem is equivalently formulated as a set of independent systems of 1-D equations in the vector Hankel transform domain for the cylindrical harmonics of the effective surface current densities. The Helmholtz decomposition of the unknowns, combined with a suitable choice of the expansion functions in a Galerkin scheme, lead to a fast-converging Fredholm second-kind matrix operator equation. Moreover, an analytical technique specifically devised to efficiently evaluate the integrals of the coefficient matrix is adopted. As shown in the numerical results section, near-field and far-field parameters are accurately and efficiently reconstructed even at the resonance frequencies of the natural modes, which are searched for the peaks of the total scattering cross-section and the absorption cross-section. Moreover, the proposed method drastically outperforms the general-purpose commercial software CST Microwave Studio in terms of both CPU time and memory occupation
Analysis of the Propagation in High-Speed Interconnects for MIMICs by Means of the Method of Analytical Preconditioning: A New Highly Efficient Evaluation of the Coefficient Matrix
No full textThe method of analytical preconditioning combines the discretization and the analytical regularization of a singular integral equation in a single step. In a recent paper by the author, such a method has been applied to a spectral domain integral equation formulation devised to analyze the propagation in polygonal cross-section microstrip lines, which are widely used as high-speed interconnects in monolithic microwave and millimeter waves integrated circuits. By choosing analytically Fourier transformable expansion functions reconstructing the behavior of the fields on the wedges, fast convergence is achieved, and the convolution integrals are expressed in closed form. However, the coefficient matrix elements are one-dimensional improper integrals of oscillating and, in the worst cases, slowly decaying functions. In this paper, a novel technique for the efficient evaluation of such kind of integrals is proposed. By means of a procedure based on Cauchy integral theorem, the general coefficient matrix element is written as a linear combination of fast converging integrals. As shown in the numerical results section, the proposed technique always outperforms the analytical asymptotic acceleration technique, especially when highly accurate solutions are required
Della causa del sonno lucido, o Studio sulla natura dell’uomo
No full textThe work was first published, in French, in Paris in November 1819 (Chez Mme Horiac). To date, no Italian version of this treatise exists and it was not until 2005 that the initial Paris edition was reprinted (Paris, Harmattan). The Sonno lucido is subdivided into XIV séances. This book occupies a strategic place in the history of hypnotism: the author is a historical personage who soon became part of popular legend and captured writers’ imagination, to the extent of becoming a myth (he features in Alexandre Dumas Père’s Le Comte de Monte-Cristo). In this book, divided into fourteen chapters, Abbé Faria illustrates the phenomenon of hypnosis – which he defines as lucid sleep – together with the results of his experiments conducted on over five thousand people. He is intent on dismantling the then widespread theory of Mesmer of “magnetic fluid”, being of the opinion that sudden “magnetic crises” of laughter or tears are not only therapeutically ineffective, but they are even detrimental and hinder the normal course of nature. In reinterpreting his predecessors in terms of a challenge, as opposed to a substantiation of his own theories, the author adopts the approach of maintaining his patients in a state of serenity. According to his original point of view – fiercely contested by the Mesmerians and by his religious opponents - hypnosis is not to be attributed to magnetism, but it is induced by the epopt’s expectations and disposition. In the light of these convictions, he unveils a modern interpretation of the ancient method of suggestion via induction or interruption of the trance, with a simple word: sleep! In recording and describing a vast range of hypnotic phenomena – currently widely known – he advances an explanation of each of these in psychological terms. He assumes, for instance, that normal sleep and the state of hypnosis partake of a similar nature. While being judged as erroneous nowadays, this theory, in the wake of Abbé Faria’s studies, has been adopted also by the School of Nancy.L’opera è stata pubblicata per la prima volta, in lingua francese, a Parigi nel novembre del 1819 (Chez Mme Horiac). A tutt’oggi non esiste una versione italiana di questo trattato e la ristampa della prima edizione parigina risale soltanto al 2005 (Parigi, Harmattan). Il Sonno lucido è suddiviso in XIV sedute (séances). Nella storia dell’ipnotismo questo libro occupa un posto fondamentale: l’autore è un personaggio storico di cui la leggenda popolare e la fantasia degli scrittori si sono impadroniti facendone un mito (è il personaggio del Conte di Montecristo di Alexandre Dumas padre). Con questo libro, frazionato in quattordici capitoli, l’Abate Faria ci dà conto del fenomeno dell’ipnosi – da lui definito sonno lucido – e del risultato dei suoi esperimenti condotti su oltre cinquemila individui. Si determina a smontare l’allora diffusa teoria di Mesmer del “fluido magnetico”, opinando che le improvvise “crisi magnetiche” di risa o di pianto non soltanto non servano a guarire, ma che siano perfino dannose e contravvengano al normale corso della natura. Nel rileggere i suoi predecessori come una sfida, anziché un conforto, l’approccio dell’autore è quello di tenere i propri pazienti in uno stato di calma. Secondo il suo originale punto di vista, contrastato duramente da mesmeriani e da oppositori religiosi, l’ipnosi non è dovuta al magnetismo, bensì è indotta dalle aspettative e dalla disposizione dell’epopte. In seguito a questi convincimenti, scopre in chiave moderna l’antico metodo di suggestione mediante induzione o interruzione della trance, con una semplice parola: dormite! Nel registrare e descrivere una vasta gamma di fenomeni ipnotici, oggi ben noti, fornisce una spiegazione psicologica di ciascuno di essi. Ha presupposto, per esempio, che il sonno normale e lo stato ipnotico siano di natura simile; teoria che, per quanto oggi sia considerata erronea, dopo gli studi dell’Abate Faria è stata adottata anche dalla Scuola di Nancy
Helmholtz–Galerkin Regularizing Technique for the Analysis of the THz-Range Surface-Plasmon-Mode Resonances of a Graphene Microdisk Stack
Get PDFThe aim of this paper is the accurate and efficient analysis of the surface-plasmon-mode resonances of a graphene microdisk stack in the terahertz range. By means of suitable generalized boundary conditions and Fourier series expansion, the problem is formulated in terms of sets of one-dimensional integral equations in the vector Hankel transform domain for the harmonics of the surface current densities. In virtue of the Helmholtz decomposition, the unknowns are replaced by the corresponding surface curl-free and divergence-free contributions. An approximate solution is achieved by means of the Galerkin method. The proper selection of expansion functions reconstructing the physical behavior of the surface current densities leads to a fast-converging Fredholm second-kind matrix equation, whose elements are accurately and efficiently evaluated by means of a suitable analytical procedure in the complex plane. It is shown that the surface-plasmon-mode resonance frequencies upshift by increasing the number of disks and by decreasing the distance between the disks, and that new resonances can arise for small with respect to the radius distances between the disks, resembling the dipole-mode resonances of the dielectric disk, while, for larger distances, the surface-plasmon-mode resonances can split
Examples of analytically regularized scattering problems via Helmholtz decomposition and Galerkin method
No full text
Electromagnetic Scattering from a Graphene Disk: Helmholtz-Galerkin Technique and Surface Plasmon Resonances
No full textThe surface plasmon resonances of a monolayer graphene disk, excited by an impinging plane wave, are studied by means of an analytical-numerical technique based on the Helmholtz decomposition and the Galerkin method. An integral equation is obtained by imposing the impedance boundary condition on the disk surface, assuming the graphene surface conductivity provided by the Kubo formalism. The problem is equivalently formulated as a set of one-dimensional integral equations for the harmonics of the surface current density. The Helmholtz decomposition of each harmonic allows for scalar unknowns in the vector Hankel transform domain. A fast-converging Fredholm second-kind matrix operator equation is achieved by selecting the eigenfunctions of the most singular part of the integral operator, reconstructing the physical behavior of the unknowns, as expansion functions in a Galerkin scheme. The surface plasmon resonance frequencies are simply individuated by the peaks of the total scattering cross-section and the absorption cross-section, which are expressed in closed form. It is shown that the surface plasmon resonance frequencies can be tuned by operating on the chemical potential of the graphene and that, for orthogonal incidence, the corresponding near field behavior resembles a cylindrical standing wave with one variation along the disk azimuth
- …
