Rappresentazione in dimensioni ridotte di documenti mediante i centroidi e i minimi quadrati

Questo elaborato ha l'obiettivo di presentare alcuni metodi di riduzione di dimensione mediante fattorizzazione di matrici. In particolare ci si soffermerà sulla riduzione di dimensione di documenti: essi vengono rappresentati come vettori le cui componenti contano le occorrenze di un termine all'interno del documento. Oltre ai metodi classici, si introdurranno due metodi recenti di riduzione e un algoritmo di classificazione che tengono conto della conoscenza a priori dei dati. L'importanza di una buona riduzione di dimensione è legata all'estrapolazione di informazioni da grandi moli di dati; in essa il maggior costo computazionale è dato dal confronto tra due documenti/vettori. Si vogliono quindi ridurre le dimensioni dei vettori senza perdere troppe informazioni su di essi. Si considereranno set di dati con una struttura di cluster e ci si soffermerà sulla loro riduzione ai fini di una corretta classificazione

Masked unbiased principles for parameter selection in variational image restoration under Poisson noise

In this paper we address the problem of automatically selecting the regularization parameter in variational models for the restoration of images corrupted by Poisson noise. More specifically, we first review relevant existing unmasked selection criteria which fully exploit the acquired data by considering all pixels in the selection procedure. Then, based on an idea originally proposed by Carlavan and Blanc-Feraud to effectively deal with dark backgrounds and/or low photon-counting regimes, we introduce and discuss the masked versions—some of them already existing—of the considered unmasked selection principles formulated by simply discarding the pixels measuring zero photons. However, we prove that such a blind masking strategy yields a bias in the resulting principles that can be overcome by introducing a novel positive Poisson distribution correctly modeling the statistical properties of the undiscarded noisy data. Such distribution is at the core of newly proposed masked unbiased counterparts of the discussed strategies. All the unmasked, masked biased and masked unbiased principles are extensively compared on the restoration of different images in a wide range of photon-counting regimes. Our tests allow to conclude that the novel masked unbiased selection strategies, on average, compare favorably with unmasked and masked biased counterparts

Acoustic measurements of the Roman theatre of Pompei by mapping the sound reflections

The city of Pompei has been always subject to archaeological works during the last decades. However, the theatre that has been discovered in the urban environment has one of the best preserved cavea, although it lacks most of the scaenae frons. This paper deals with the acoustic measurements undertaken to study the behavior of this important monument through the main acoustic parameter outlined by ISO 3382-1, and to detect the direction of the early and late reflections characterizing the reverberation. This latest approach enabled the possibility to investigate the sound propagation thought the space with the employment of a multichannel spherical array microphone. The recorded impulse response (IR) has been analyzed in such a way to create an overlay video, given by the overlapping of the 360° image taken at the receiver position with the contour level of the sound decay after the impulse

Comparison Failure and Successful Methodologies for Diffusion Measurements Undertaken inside Two Different Testing Rooms

The scattering phenomenon is known to be of great importance for the acoustic quality of a performance arts space. The scattering of sound can be achieved in different ways: it can be obtained by the presence of architectural and/or decorating elements inside a room (e.g., columns, statues), by the geometry and roughness of a surface (e.g., Quadratic Residue Diffuser (QRD)) and by the diffraction effect occurring when a sound wave hits the edges of an obstacle. This article deals with the surface scattering effects and the diffusion phenomenon only related to MDF and plywood panels tested by disposing the wells both horizontally and vertically. The test results undertaken inside a semi-reverberant room and inside a large reverberant room have been compared to highlight the success and the failure of the measuring methodologies. In detail, according to the existing standards and regulations (i.e., ISO 17497—Part 2), diffusion measurements have been undertaken on a few selected types of panel: two QRD panels (made of Medium Density Fiberboard (MDF) and plywood) with and without a smooth painted solid wood placed behind the QRD. The panels have been tested inside two rooms of different characteristics: a semi-anechoic chamber (Room A) and a large reverberant room (Room B). The volume size influenced the results that have been analyzed for both chambers, showing an overlap of reflections on panels tested inside Room A and a clear diffusion response for the panels tested inside Room B. In terms of the diffusion coefficient in all the octave bands between 125 Hz and 8 kHz, results should not be considered valid for panels tested in Room A because they were negatively impacted by extraneous reflections, while they are reliable for panels tested in Room B

Metabiotic effects of Fusarium spp. on Escherichia coli O157:H7 and Listeria monocytogenes on raw portioned tomatoes.

The metabiotic effects of Fusarium proliferatum, F. avenaceum, and F. oxysporum on Escherichia coli O157:H7 and Listeria monocytogenes in fresh tomatoes were investigated. Tomatoes were preinoculated with the molds and incubated at 15 degrees C for 7 days; then they were inoculated separately with the pathogens, packaged in air and modified atmosphere (5% O2, 30% CO2, and 65% N2), and stored at 4, 8, and 12 degrees C for 9 days. The cell loads of pathogens and lactic acid bacteria and the pH were evaluated periodically. The data were modeled through some different mathematical models to assess the shoulder length, i.e., the time before the beginning of the exponential death phase, the 1-log reduction time (s), and the pathogen death time (deltastand). The preinoculation of tomatoes with the molds enhanced the survival of E. coli O157:H7 by prolonging shoulder length and 8 parameters; this effect, however, was not observed for L. monocytogenes. pH values did not undergo significant changes within the storage time, and the lactic acid bacteria increased from 5 to 7 log CFU/g, without significant differences among the storage temperatures or the packaging atmospheres. The results of this research showed that the use of fresh tomatoes colonized by fusaria (even if the contamination is not visible) could increase significantly the risk of outbreaks due to some pathogens that could be on the surface of fruits and vegetables as a result of cross-contamination at home or incorrect postharvest operations

Modelling the Survival of Escherichia coli O157:H7 on Raw Portioned Tomatoes, Inoculated with Aspergillus fumigatus and Emericella nidulans

The metabiotic interactions occurring among two fungi (Aspergillus fumigatus and Emericella nidulans) and Escherichia coli O157:H7 on raw portioned tomatoes were studied. Tomatoes, preinoculated with the moulds and inoculated with the pathogen, were packaged in air and stored at 4, 8 and 12∘C for 9 days; pathogen cell number and pH were monitored throughout the storage and the data were modeled using three different equations (Geeraerd, Weibull, and modified Weibull), to assess the shoulder length, the 1-log reduction time, and the death time. Both A. fumigatus and E. nidulans increased the survival of E. coli O157:H7 through the prolongation of the shoulder length; in contrast, the death time was significantly increased. The results of this paper suggested that the metabiotic interactions aspergilli/E. coli O 157:H7 could be of public concern, as the consumption of tomatoes (or other fruits and vegetables) contaminated both by the moulds and the pathogen is a possible scenario

Sleep Quality, Emotion Regulation and Parenting Stress in Children with Congenital Heart Disease

The aim of this study is to evaluate parental perceptions of parent-infant bedtime interactions and quality of sleep, after hospital discharge, in a group of children diagnosed at birth with congenital heart disease (CHD), as compared with the perceptions of parents in a control group of children who were healthy at birth. More specifically, we evaluated the associations between parental stress, parental perceptions of infant emotion regulation, and infants’ bedtime and sleep routines in each of the two groups. Fifty Italian intact two-parent families (23 boys) of toddlers ageing from 11 to 36 months (M= 23.42, SD=7.10) were recruited. 20 families of CHD children group were recruited from the Department of Cardiology at the Bambino Gesù Children’s Hospital in Rome, Italy; 30 families of the healthy children group were recruited from two childcare units. Parents completed Emotion Regulation Checklist (Shields Cicchetti, 1997), Parent-Child Sleep Interaction Scale (PSIS; Alfano et al., 2013), Parent-Stress Index-Short Form (PSI-SF; Abidin, 1990) and ad-hoc semi-structured interview on child’s sleep quality. The independent-samples t-test evidenced that parents of healthy children reported significantly higher scores on children's emotion regulation compared with the CHD group Specifically CHD children and healthy children's emotion regulation reported both by mothers (respectively CHD children’s mothers: M= 26.11, SD= 2.9; healthy children’s mothers: M= 28.85, SD= 2.71; t(37) = 3.10, p= .004) and fathers (respectively CHD children’s fathers: M=25.76, SD= 2.79; healthy children’s fathers: M= 27.37, SD= 2.02; t(31)= 2.71, p= .010). Main correlational findings showed in the CHD children’s group that parenting stress total scores were positive related to difficult parent-infant bedtime interactions both for mothers (r=.58, p .01) and fathers (r= .70, p .01). Results show significant differences in emotion regulation between the two groups. The results of this research will show to the clinicians the aspects of parent-infant bedtime interactions to be addressed in parents of children with CHD

Acoustic parameters of the Municipal Theatre of Piacenza shown on different ways of representation

The Italian Opera theatres are always subject to scientific studies that try to investigate as deeply as possible this historical heritage to preserve the architectural and acoustical information for future generations. This paper deals with two ways of data representations based on the outcomes derived from the variety of equipment used during the measurements. In particular, a methodology in line with standards and regulations has been introduced to representing the graphs of the main acoustical parameters; besides, a video of the real-time room impulse response (RIR) has been snapped with a few shots in place of visualizing the sound reflections that occurred inside the entire volume. After a brief description of the historical background of the Municipal theatre of Piacenza, the authors introduce the two methods just discussed to highlight the completeness of data representation regarding any type of room that is intended to be analyzed acoustically