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Threshold Behavior in Light Reflection Tuning the Disorder in Photonic Media
No full textThe optical properties of materials are strongly influenced by disorder. Control of disorder in photonic materials can unveil interesting optical properties. We have found an engineered photonic structure for which the average light reflection shows a linear behavior with a slope change in a broad range of wavelengths. Such change in slope is due to a specific degree of disorder, which is quantified by the Shannon index
Inhomogeneous two-dimensional photonic media: A statistical study
No full textPhotonic media, in which disorder is introduced, are interesting materials for light management. In this paper, we have performed a statistical study of the average light transmission, over the range of wavelengths 450-1400 nm, for two-dimensional photonic structures with different homogeneity (quantified by the Shannon index). The photonic structure is a square lattice of circular pillars and the homogeneity is varied by clustering pillars in the crystal unit cells. We have calculated the light transmission for 50 different crystal realizations (permutating cluster position in the crystal) for each Shannon index value. Such Monte Carlo Markov Chain method produced the "a posteriori" distribution of the light transmission. We have observed a linear trend of the average transmission as a function of the crystal homogeneity. Furthermore, we have found a linear dependence of the average light transmission on the mean distance between pillars in the photonic structures
Light transmission behaviour as a function of the homogeneity in one dimensional photonic crystals
No full textThe average light transmission of one-dimensional photonic media has been studied as a function of the medium homogeneity, quantified by the Shannon Wiener index. We have found a decrease in the average light transmission by increasing the Shannon Wiener index up to minimum (corresponding to H' = 0.9375): from this point, the transmission increases following the Shannon Wiener index. The behaviour has been confirmed for different pairs of materials forming the photonic structure. Nevertheless, we have observed that the trend slope is proportional to the refractive index ratio between the two materials (n(hi)/n(low))
Robustness of empirical food webs with varying consumer’s sensitivities to loss of resources.
No full textLight Transmission Properties and Shannon Index in One-Dimensional Photonic Media With Disorder Introduced by Permuting the Refractive Index Layers
Full text linkIn this paper, we have studied, with a numerical method, how introducing disorder affects the light transmission properties of 1-D photonic structures over a wide range of wavelengths. A new type of disorder is introduced by permuting the refractive index layers in the optical medium. We compared the light transmission properties of ideal photonic crystals and of disordered media with the same kind and number of scattering elements for different sample lengths. We have calculated the transmission properties, by the transfer matrix method, of thousands of different disordered structures in order to perform a statistical analysis. We found that, below a certain sample length, disorder induces less average light reflection than ordered structures, whereas above the threshold length, disordered structures show more average reflection. Moreover, we have quantified the disorder of the structures with the Shannon index. We have found a decrease in the average light transmission as a function of the Shannon index. Furthermore, the sample length affects the trend of the average transmission as a function of the Shannon index
Preliminary study by habitat modeling of bottlenose dolphin (Tursiops truncatus) distribution along the east coast of Liguria (North West Mediterranean Sea)
No full textMODELLIZZAZIONE DELL’HABITAT DEL TURSIOPE NEL MAR LIGURE DI LEVANTE: TRE DIVERSI APPROCCI
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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