1,721,553 research outputs found
Household crowding during the COVID-19 lockdown fosters anti-democracy even after 17 months: A 5-wave latent growth curve study
Get PDFIn an earlier cross-sectional study, Roccato et al. (2021) showed that household crowding during the COVID-19 lockdown was positively related to support for anti-democratic political systems. However, little is known about the persistence of these effect over time. In this study, we examined its duration in a longitudinal study structured in five waves, the first in May–June 2019 (before the COVID-19 outbreak, N = 1504) and the others during the pandemic, in April 2020 (during the lockdown, N = 1199), October 2020 (N = 1156), April 2021 (N = 1148), and October 2021 (N = 1151). The increase in support for anti-democratic systems associated with household overcrowding in the initial phase of the lockdown (Wave 2) did not change over the subsequent 17 months. Moreover, the effect was stronger among those who had high (compared with low) trust in democratic political institutions before the pandemic. Strengths, limitations, and potential developments of the study are discussed
M. Roccato e T. Mannarini, Non nel mio giardino. Prendere sul serio i movimenti Nimby
No full textRecensione del volume di M. Roccato e T. Mannarini, Non nel mio giardino. Prendere sul serio i movimenti Nimb
Metodo di telerilevamento di dati e telecontrolli via radio mediante connessione permanente tra postazioni periferiche ed una postazione centrale tramite postazioni intermedie fisse
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Reliability and efficiency-limiting mechanisms in III-N LEDs: an experimental analysis assisted by numerical simulations
No full textThis thesis reports a deep investigation on light-emitting diodes (LEDs) at the current state-of-art in both visible and UV ranges of emission and focusses on the defect- and temperature-related loss processes that affect these devices limiting their efficiency and reliability. The analysis studies LED samples fabricated in collaboration with the École Polytechnique Fédérale de Lausanne (EPFL) and the Technische Universität Berlin (TUB). In particular this research activity includes (a) an experimental characterization of the crystallographic defects present in the devices by means of deep level optical-spectroscopy and Light capacitance-voltage measurements; (b) the evaluation of the device reliability through accelerated stress test and the identification of the mechanisms involved in the degradation; (c) a modeling of the electrical characteristics of LEDs based on the experimental results and of their behavior during ageing and (d) the design of a set-up for fast electro-optical characterization of high-power devices in order to measure the self-heating transients and evaluate the impact of heating in the LED performance. In particular this study demonstrates that in InGaN/GaN LEDs:
I) The defects are preferentially incorporated in indium-containing layers such as under layers and quantum wells. Their density is proportional to In-content and, if incorporated within the active region, they negatively affect the reliability of the devices contributing to their optical degradation.
II) The superlattice underlayer effectively contributes to reduce the defectiveness of the active region, partially preventing the defect propagation toward the QW.
III) It is possible to model the electrical characteristic starting from the defect characterization and considering their correlated leakage mechanisms such as trap-assisted tunneling. Furthermore, the model can reproduce the behavior of the device under ageing contributing to the identification of the degradation physical mechanisms.
IV) An increase in defects at the QW interfaces influence the optical behavior, alternating the injection of the carriers into the QW.
Whereas, for UV-C AlGaN-based LEDs:
I) An increase in the defect density has been identified during LED ageing. This increase that affects the electrical characteristic mainly involves the region from the electron-blocking layer (EBL) toward the active region. A possible cause of degrade is migration of impurities, such as hydrogen, as a result of the high p-doping density in the EBL.
II) In the region adjacent to the contact, a doping passivation process would generate a loss in the injection efficiency and consequently, a shift of the turn-on voltage during the stress test.
Finally, the designed setup for the self-heating characterization of high-power LEDs leads to the following advantages:
I) The circuit allows the measurement of the self-heating transients of voltage and optical power at high currents (up to 2A) from 6 μs with a high stability (<0.1%) and accuracy. It is thus possible to analyze the variation in optical emission and extrapolate the value of the thermal impedance;
II) The measurement of the heating transients is carried out directly at high current, rather than at low current recording the cooling transients as performed by the traditional technique;
III) The pulsed electro-optical and spectra measurements allow us to extract information on the LED performance before the self-heating transient or at a specified junction temperature;
IV) The spectrum of the device can be monitored during all the heating transient starting from about 10 μs. This allows a correct estimation of the decrease in optical power and the analysis of the phosphor behavior during the heating
Are we gaining or losing ground? Dynamic perceptions of public opinion influence willingness to speak out and participate in land use conflicts
Get PDFUsing an Italian land use conflict on the building a high-speed
railway (HSR) as case study, we analyzed how perceived changes
in public opinion influence (a) people’s willingness to speak out,
and (b) subsequently their intentions to engage in action (N = 311).
Regardless of whether they were on the majority or minority side of
the conflict, citizens’ willingness to speak out was positively asso-
ciated with their perceptions that their position was becoming
more or less widespread within public opinion, especially among
participants with extreme attitudes toward the HSR. Willingness to
speak out about the HSR mediated the relation between increasing
support discrepancy and intention to participate in the conflict.
Strengths, limitations and implications are discussed
How regularities shape visual perception: aesthetic preferences, form discrimination, and geometric hallucinations
No full textThe human visual system efficiently processes complex visual information by integrating regularities across space and time, such as symmetry, geometrical form, and temporal frequency, to ultimately create coherent percepts. However, open questions remain about how the visual system encodes such regularities and at which stages along its processing hierarchy they are integrated. This thesis illustrates three visual perception studies: one exploring the role of context-based symmetry in aesthetic preference, and the remaining two investigating the spatial and temporal dynamics underlying form perception, with a focus on veridical and illusory geometric patterns respectively. In the first study, the role of bilateral symmetry on aesthetic judgments was examined across various stimuli, including abstract shapes, landscapes, flowers, and human faces. These images were shown to viewers, asking them to provide explicit aesthetic ratings and engage in an Implicit Association Test (IAT) to collect implicit behavioral measures. Interestingly, implicit measures demonstrated indiscriminate positive associations between symmetry and goodness across image categories of interest, whereas explicit measures showed a more nuanced pattern with respect to the aesthetic impact of symmetry in the same categories. These findings suggest a dissociation between implicit and explicit measures of human appreciation for symmetry when this feature is embedded in different types of objects and scenes. The second study investigated form and motion integration using Glass patterns (GPs), a class of visual stimuli in which global structure emerges from locally oriented dot pairs. Static GPs consist of a single-frame ensemble of dot pairs arranged in a fixed configuration, whereas dynamic GPs are built through the close temporal juxtaposition of frames displaying different configurations. By manipulating the number of unique frames and the pattern update rate, we investigated the impact of these two factors on discrimination thresholds for circular, radial, and spiral dynamic GPs. Results replicated previous findings that circular GPs are more easily perceived than radial and spiral GPs, exhibiting lower discrimination thresholds. Additionally, discrimination thresholds decreased with an increasing number of unique frames, while the effect of the pattern update rate was negligible. These findings hint at a mechanism of summation of form signals sampled from unique frames, but do not clearly support temporal integration based on the update rate. In the third study, the effects of flicker frequency and rhythmicity on geometric form perception were explored using flicker light stimulation. Participants were exposed to four different types of luminance flicker, resulting from the combination of two levels of frequency with two levels of rhythmicity. Electroencephalography (EEG) was used to record neural responses to flicker light stimulation. Participants were asked to categorize ambiguous static GPs featuring a mixture of radially- and spirally-oriented dot pairs. Behavioral data revealed that the probability of categorizing a pattern as radial or spiral varied with flicker frequency, with a stronger and temporally accruing bias observed under rhythmic flicker conditions. Overall, these experiments demonstrate how complex interactions of spatial and temporal regularities in visual input can affect human vision at different levels, influencing both perceptual decision- making and aesthetic judgments. The findings contribute to a broader understanding of how visual perception mechanisms rely on regularity to make sense of the world around us
Lega and Five-star Movement voters: exploring the role of cultural, economic and political bewilderment
Get PDFWe explore the motivations behind the electoral success of the Lega and the Five-star Movement at the 2018 Italian general election. In most of the literature on populism, the success of the new European populist parties is interpreted as stemming from the process of globalisation, which has produced the so-called ‘modernisation losers’: ‘cultural losers’ (people who are disorientated by changes in values, by new waves of migration and by the loss of national sovereignty to the European Union) and ‘economic losers’ (those for whom the globalisation process has meant economic hardship, downward social mobility and occupational uncertainty). It is these ‘modernisation losers’ who are claimed to have voted for the populist parties. To this two-fold theoretical hypothesis, we added another: the rise in populism can be explained by the democratic malaise, and particularly by the crisis of mainstream parties, which have steadily lost their function as a link between the people and politics. We analyse the role of these three antecedents of populism – labelled as cultural, economic and political – drawing on 2018 Italian National Election Studies (ITANES: see www.itanes.org/en) data. Votes for the Lega were motivated by ‘cultural populism’, while those for the Five-star Movement could be ascribed to ‘political populism’, stemming from citizens’ growing mistrust – generalised and latent in Western democracies – of political institutions, activated in Italy by favourable structural conditions and external circumstances
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