101,961 research outputs found
Correction: G. Papari et al. Terahertz spectroscopy of amorphous wse2 and mose2 thin films. Materials (2018), 11(9), 1613[Materials 2020, 13, 1017] DOI: 10.3390/ma13041017
No full textThe exponential factor in Equation (1) of the paper published in Materials [1] reports a misprint and the correct expression of the transmission function is These changes have no material impact on the conclusions of the paper. The authors would like to apologize for any inconvenience caused to the readers by these changes. Conflicts of Interest: The authors declare no conflict of interest
Tafuri F, Stornaiuolo D, Lucignano P, Galletti L, Longobardi L, Massarotti D, Montemurro D, Papari G, Barone A, Tagliacozzo A
No full textInterplay between the quantum interference and current localization phenomena in superconductor non-ideal mesoscopic rings
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New Families of Fourier Eigenfunctions for Steerable Filtering
No full textA new diadic family of eigenfunctions of the 2-D Fourier transform has been discovered. Specifically, new wavelets are derived by steering the elongated Hermite–Gauss filters with respect to rotations, thus obtaining a natural generalization of the Laguerre–Gauss harmonics. Interestingly, these functions are also proportional to their 2-D Fourier transform. Their analytical expression is provided in a compact and treatable form, by means of a new ad hoc matrix notation in which the cases of even and odd orders of the Hermite polynomials are unified. Moreover, these functions can be efficiently implemented by means of a recursive formula that is derived in this paper. The proposed filters are applied to the problem of gradient estimation to improve the theoretical Canny tradeoff of position accuracy versus noise rejection that occurs in edge detection. Experimental results show considerable improvements in using the new wavelets over both isotropic Gaussian derivatives and other elongated steerable filters more recently introduced. Finally, being the proposed wavelets a set of Fourier eigenfunctions, they can be of interest in other fields of science, such as optics and quantum mechanics.
Geometrical Dependence on the Onset of Surface Plasmon Polaritons in THz Grid Metasurfaces
No full textThe transmission response of metallo-dielectric grid metasurfaces is experimentally investigated
through Terahertz Time Domain Spectroscopy and the corresponding effective dielectric function is retrieved. Using a lumped element model we can determine the dependence of the effective plasma frequency (the transition frequency) on the metasurface filling factor F. The change of the transition frequency vs. F spans over one order of magnitude and sets the threshold between the metamaterial (homogeneous) and the photonic crystal (diffraction-like) regime, ruling the onset of two different Surface Plasmon Polaritons, spoof and high order. Field symmetry and spatial extension of such excitations are investigated for the possible applications of THz grid metasurfaces in bio- and chemical sensing and sub-wavelength imaging
Artistic Edge and Corner Enhancing Smoothing
No full textTwo important visual properties of paintings and painting-like images are the absence of texture details and the increased sharpness of edges as compared to photographic images. Painting-like artistic effects can be achieved from photographic images by filters that smooth out texture details, while preserving or enhancing edges and corners. However, not all edge preserving smoothers are suitable for this purpose. We present a simple nonlinear local operator that generalizes both the well known Kuwahara filter and the more general class of filters known in the literature as “criterion and value filter structure.” This class of operators suffers from intrinsic theoretical limitations which give rise to a dramatic instability in presence of noise, especially on shadowed areas. Such limitations are discussed in the paper and overcome by the proposed operator. A large variety of experimental results shows that the output of the proposed operator is visually similar to a painting. Comparisons with existing techniques on a large set of natural images highlight conditions on which traditional edge preserving smoothers fail, whereas our approach produces good results. In particular, unlike many other well established approaches, the proposed operator is robust to degradations of the input image such as blurring and noise contamination.
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