arXiv subjects

Amelia Sparavigna

Publications and source records attributed to Amelia Sparavigna.

14 recordsLinked to original sources

arXiv2020

The k-statistics approach to epidemiology

A great variety of complex physical, natural and artificial systems are governed by statistical distributions, which often follow a standard exponential function in the bulk, while their tail obeys the Pareto power law. The recently introduced $κ$-statistics framework predicts distribution functions with this feature. A growing number of applications in different fields of investigation are beginning to prove the relevance and effectiveness of $κ$-statistics in fitting empirical data. In this paper, we use $κ$-statistics to formulate a statistical approach for epidemiological analysis. We validate the theoretical results by fitting the derived $κ$-Weibull distributions with data from the plague pandemic of 1417 in Florence as well as data from the COVID-19 pandemic in China over the entire cycle that concludes in April 16, 2020. As further validation of the proposed approach we present a more systematic analysis of COVID-19 data from countries such as Germany, Italy, Spain and United Kingdom, obtaining very good agreement between theoretical predictions and empirical observations. For these countries we also study the entire first cycle of the pandemic which extends until the end of July 2020. The fact that both the data of the Florence plague and those of the Covid-19 pandemic are successfully described by the same theoretical model, even though the two events are caused by different diseases and they are separated by more than 600 years, is evidence that the $κ$-Weibull model has universal features.

q-bio.PE↗

arXiv2009

Color Dipole Moments for Edge Detection

Dipole and higher moments are physical quantities used to describe a charge distribution. In analogy with electromagnetism, it is possible to define the dipole moments for a gray-scale image, according to the single aspect of a gray-tone map. In this paper we define the color dipole moments for color images. For color maps in fact, we have three aspects, the three primary colors, to consider. Associating three color charges to each pixel, color dipole moments can be easily defined and used for edge detection.

cs.CV↗

arXiv2009

Digital Restoration of Ancient Papyri

Image processing can be used for digital restoration of ancient papyri, that is, for a restoration performed on their digital images. The digital manipulation allows reducing the background signals and enhancing the readability of texts. In the case of very old and damaged documents, this is fundamental for identification of the patterns of letters. Some examples of restoration, obtained with an image processing which uses edges detection and Fourier filtering, are shown. One of them concerns 7Q5 fragment of the Dead Sea Scrolls.

cs.CV↗

arXiv2009

The Digital Restoration of Da Vinci's Sketches

A sketch, found in one of Leonardo da Vinci's notebooks and covered by the written notes of this genius, has been recently restored. The restoration reveals a possible self-portrait of the artist, drawn when he was young. Here, we discuss the discovery of this self-portrait and the procedure used for restoration. Actually, this is a restoration performed on the digital image of the sketch, a procedure that can easily extended and applied to ancient documents for studies of art and palaeography.

cs.CV↗

arXiv2009

Dipole Vectors in Images Processing

Instead of evaluating the gradient field of the brightness map of an image, we propose the use of dipole vectors. This approach is obtained by adapting to the image gray-tone distribution the definition of the dipole moment of charge distributions. We will show how to evaluate the dipoles and obtain a vector field, which can be a good alternative to the gradient field in pattern recognition.

cs.CV↗

arXiv2009

Dipole and Quadrupole Moments in Image Processing

This paper proposes an algorithm for image processing, obtained by adapting to image maps the definitions of two well-known physical quantities. These quantities are the dipole and quadrupole moments of a charge distribution. We will see how it is possible to define dipole and quadrupole moments for the gray-tone maps and apply them in the development of algorithms for edge detection.

cs.CV↗

arXiv2008

The Pleiades: the celestial herd of ancient timekeepers

In the ancient Egypt seven goddesses, represented by seven cows, composed the celestial herd that provides the nourishment to her worshippers. This herd is observed in the sky as a group of stars, the Pleiades, close to Aldebaran, the main star in the Taurus constellation. For many ancient populations, Pleiades were relevant stars and their rising was marked as a special time of the year. In this paper, we will discuss the presence of these stars in ancient cultures. Moreover, we will report some results of archeoastronomy on the role for timekeeping of these stars, results which show that for hunter-gatherers at Palaeolithic times, they were linked to the seasonal cycles of aurochs.

physics.hist-ph↗

arXiv2008

Recurrence plots of sunspots, solar flux and irradiance

The paper shows the recurrence and cross recurrence plots of three time series, concerning data of the solar activity. The data are the sunspot number and the values of solar radio flux at 10.7 cm and of solar total irradiance, which are known as highly correlated. To compare the series, the radio flux and irradiance values are monthly averaged. Recurrence plots display the oscillating behaviour with remarkable features. Moreover, cross recurrence plots help in identifying time lags between the sunspot number maximum and the maximum of radio or irradiance signals, in circumstances where the data values are highly dispersed. Image processing is useful too, in enhancing the monitoring. An interesting behaviour is displayed by cross recurrence plots of irradiance, which are not symmetric with respect to the line of identity.

physics.pop-ph↗

arXiv2008

A survey of liquid crystalline oxadiazoles

We propose a survey of those oxadiazole compounds, which are mesogenic. We will see that they can have bend-shaped molecules, a biaxial nematic phase, or other interesting peculiarities in the nematic and smectic phase. With large electric dipoles and luminescent properties, these materials are also very appealing for technological applications.

cond-mat.soft↗

arXiv2008

Plasma treatment advantages for textiles

The textile industry is searching for innovative production techniques to improve the product quality, as well as society requires new finishing techniques working in environmental respect. Plasma surface treatments show distinct advantages, because they are able to modify the surface properties of inert materials, sometimes with environment friendly devices. For fabrics, cold plasma treatments require the development of reliable and large systems. Such systems are now existing and the use of plasma physics in industrial problems is rapidly increasing. On textile surfaces, three main effects can be obtained depending on the treatment conditions: the cleaning effect, the increase of microroughness (anti-pilling finishing of wool) and the production of radicals to obtain hydrophilic surfaces. Plasma polymerisation, that is the deposition of solid polymeric materials with desired properties on textile substrates, is under development. The advantage of such plasma treatments is that the modification turns out to be restricted in the uppermost layers of the substrate, thus not affecting the overall desirable bulk properties. Here, we present the research results on the use of plasma physics in textile properties modification. Treatments on natural, wool and cotton, and on synthetic polymers to improve wetting are shown. Hydrophilic-hydrophobic treatments, dirt-repellent coatings are presented. Low-pressure and atmospheric-pressure glow discharge systems are also discussed.

physics.pop-ph↗

arXiv2008

Fourier optics for polymeric substrates and coating textures analysis

Several devices for substrate texture detection based on diffractive optics, for paper, textiles and non-wovens have been proposed in the past for direct inspection during the production processes. In spite of the presence of devices totally based on image processing, the use of diffractive optics cannot be considered surpassed for many reasons. Compared with image processing procedures, it is less sensitive to vibrations and does not suffer from the presence of ambient light. Based on transmitted light, it can give information on changes in refractive indexes, thickness variation and surface conditions. We study the use of optical Fourier spectrum to identify textures of polymer films. As the power spectrum reveals, the texture is seldom homogeneous. Here we report investigation on several substrates and on thin ink coatings on substrate. Role of bulk and surface conditions is analysed.

physics.pop-ph↗

arXiv2008

Physics in Carnacki's investigations

In the stories of Carnacki, created by the English writer William H. Hodgson and written between 1910 and 1912, we find an interesting mixture of science and fantasy. In spite of the fact that Carnacki is a ghost finder, who investigates in an environment where supernatural is acting, we see the character using technology and sometimes discussing of physics phenomena such as X-rays. The Carnacki's stories can be seen as mirrors of the physics and technology knowledge at the beginning of Twentieth Century, in the society outside scientific circles.

physics.pop-ph↗

arXiv2008

Labels discover physics: the development of new labelling methods as a promising research field for applied physics

Labels and tags are accompanying us in almost each moment of our life and everywhere we are going, in the form of electronic keys or money, or simply as labels on products we are buying in shops and markets. The label diffusion, rapidly increasing for logistic reasons in the actual global market, carries huge amount of information but it is demanding security and anti-fraud systems. The first crucial point, for the consumer and producer safety, is to ensure the authenticity of the labelled products with systems against counterfeiting and piracy. Recent anti-fraud techniques are based on a sophisticated use of physical effects, from holograms till magnetic resonance or tunnel transitions between atomic sublevels. In this paper we will discuss labels and anti-fraud technologies as a new and very promising research field for applied physics.

physics.pop-ph↗

arXiv2007

On the role of Lifshitz invariants in liquid crystals

The interaction between an external action and the order parameter, via a dependence described by a so-called Lifshitz invariant, is very important to determine the final configuration of the liquid crystal cells. The external action can be an electric field applied to the bulk or the confinement due to free surfaces or cell walls. The Lifshitz invariant includes the order parameter in the form of an elastic strain. This coupling between elastic strains and fields, inserted in a Landau-Ginzburg formalism, is well known and give rise to striction effects causing undulations in the director configuration. We want to discuss here the role of Lifshitz coupling terms, following an approach similar to that introduced by Dzyaloshinskii for magnetic materials. Case studies on nematics in planar and cylindrical cells are also proposed.

cond-mat.soft↗