279 research outputs found
Nanoseismic monitoring for detection of rockfalls. Experiments in quarry areas
Le frane per crollo da ammassi rocciosi fratturati sono tra i processi di instabilità gravitativa che più frequentemente interessano opere antropiche quali tagli su versanti naturali o artificiali, pareti di cava, trincee stradali, autostradali o ferroviarie, sia per ciò che attiene le aree di distacco che per quelle di accumulo. Nell’ambito dell’applicazione di sistemi di early warning per la gestione del rischio geologico legato a queste tipologie di frana, una sperimentazione della tecnica del monitoraggio nanosismometrico è stata effettuata presso due siti estrattivi non più in attività : le “Pirrere” della Baia di Cala Rossa sull’isola di Favignana (Trapani), in Sicilia, e la cava dismessa di Acuto (Frosinone), in Italia Centrale. Il monitoraggio nanosismometrico è una tecnica di indagine che consente di individuare e localizzare deboli eventi sismici, fino a magnitudo locale (ML) nell’ordine di -3, attraverso l’impiego di quattro sensori sismometrici disposti secondo una specifica geometria di array detta SNS (Seismic Navigation System).
Nel presente lavoro, mediante il software NanoseismicSuite sono stati analizzati 73 eventi di crollo indotti artificialmente attraverso la caduta controllata di blocchi di roccia nei due siti estrattivi abbandonati; sono stati lanciati, simulando fenomeni di rockfalls, rispettivamente 47 blocchi di roccia nella cava di Acuto e 26 eventi in quattro diverse cave a cielo aperto presenti nel settore occidentale di Cala Rossa. Tali eventi, avendo punto epicentrale noto, hanno permesso di determinare il miglior modello di sottosuolo in termini di valori di velocità delle onde P ed S attraverso un’operazione di back analysis. L’analisi è stata, infatti, effettuata variando i valori di velocità e scegliendo quelli relativi all’epicentro teorico ottenuto dall’analisi dell’evento che fosse il più vicino possibile al punto reale di impatto del blocco di roccia. Al fine di valutare la sensibilità della geometria dell’array SNS e l’influenza del sito di installazione sulla capacità di individuare e localizzare gli eventi, le sperimentazioni sono state condotte sia variando il raggio di apertura che la zona di installazione degli array: presso Acuto le acquisizioni di segnale sono state condotte prima con un array SNS con apertura di 20 m e successivamente con un array di apertura 10 m, mentre presso Cala Rossa l’array è stato installato alternativamente all’aperto in un’area di plateau roccioso ed in una galleria facente parte dell’area di cava abbandonata.
Analizzando i dati si è ottenuta una precisione dell’ubicazione epicentrale compresa tra il 10 ed il 22% della distanza che intercorre tra la sorgente e l’array nanosismometrico. Il miglior modello di sottosuolo ottenuto per entrambi i casi di studio è risultato avere una velocità delle onde P pari a 900 m/s ed un rapporto VP/VS pari a 1.73, valori in accordo con le condizioni di intenso stato di fratturazione delle rocce carbonatiche affioranti nelle due zone di cava. Per gli eventi di crollo indotti la magnitudo ML è risultata essere compresa tra -2.8 e -1.3; considerando l’energia sviluppata dall’impatto, legata alla massa del blocco ed all’altezza e alla velocità di caduta, non è stato possibile definire una relazione tra magnitudo ed energia, probabilmente a causa delle differenti caratteristiche del punto di impatto dei diversi blocchi. In generale, si è osservato che la precisione di ubicazione degli eventi, in termini di azimuth e distanza dal reale epicentro, è risultata paragonabile sia variando l’apertura dell’array che variando il sito di installazione. Per il sito sperimentale di Acuto, il processo di picking manuale del tempo di primo arrivo delle onde P è risultato essere più affidabile nel caso di array con apertura pari a 10 m. La sperimentazione effettuata a Cala Rossa ha permesso, invece, di osservare una migliore capacità di individuazione degli eventi nelle tracce relative all’array posizionato in galleria a causa della minore rumorosità di base del sito di installazione.
Tra le registrazioni sismometriche sono state identificate varie tipologie di segnali, oltre a quelli generati dal lancio dei blocchi, alcune riconducibili ad eventi naturali di crollo altre a deboli terremoti. L’analisi dei segnali riferibili alla prima tipologia di eventi naturali, effettuata tenendo in considerazione i modelli di sottosuolo precedentemente calibrati, ha portato all’identificazione in ambedue i siti di aree aventi maggiore suscettibilità a frane per crollo. In definitiva, si può ritenere che i risultati ottenuti in questo studio siano incoraggianti rispetto all’efficacia della tecnica di monitoraggio nanosismometrico nell’individuazione e nell’ubicazione di fenomeni di crollo in roccia e portano a ritenere questa tecnica potenzialmente applicabile in aree in cui tali eventi possono interferire con infrastrutture antropiche.In the frame of early warning and risk mitigation studies for landslide processes involving rock masses, two quarry areas (Cala Rossa Bay in Sicily and Acuto in Central Italy) were monitored with SNS (Seismic Navigation System) arrays. In this study, 73 rockfalls were simulated by launches of rock blocks. This allowed to perform a back analysis for defining the best seismic velocity model of the subsoil half-space; the records related to each impact caused by the rock block launch were managed by the nanoseismic monitoring approach, varying the velocity model to obtain a theoretical epicentre as close as possible to the actual location of the impact point. In order to evaluate the sensibility of the SNS array, the results obtained by different array apertures and positions were compared in terms of azimuth and distance error with respect to the real epicentres. On the other hand, several natural rockfalls were detected; their analysis allowed to identify areas having higher susceptibility to rockfalls by using the previously calibrated subsoil half-space model. Further studies are required to better define the areas prone to rockfall generation in the considered test sites; nevertheless, the here obtained results show an encouraging perspective about the application of the nanoseismic monitoring with respect to vulnerable infrastructures in rockfall prone areas
Effect of affective priming on prosocial orientation through mobile application: Differences between digital immigrants and natives
Digital revolution has drastically changed people’s lives in the last three decades inspiring scholars to deepen the role of technologies in thinking and information processing (Baranyi et al., 2015). Prensky (2001) has developed the notion of digital generation, differentiating between natives and immigrants. Digital natives are characterised by their highly automatic and quick response in hyper-textual environment. Digital immigrants are characterised by their main focus on textual elements and a greater proneness to reflection. The main goal of the present research is to investigate the effect of affective priming on prosocial orientation in natives and immigrants by using a mobile application. A quasi-experimental study has been conducted to test whether and how the manipulation of the priming, through positively and negatively connoted images, influences prosocial orientation. The results attested that negative affective priming elicited by app influences negatively prosocial orientation, while positive affective priming influences it positively prosocial orientation. However, this effect is true mainly for digital natives. Overall, findings underline the relevance of taking into account the effects of affective priming in technological environment, especially in the case of digital natives
Self-efficacy configurations and wellbeing in the academic context: A person-centred approach
The aim of the present study was to identify self-efficacy configurations in different domains (i.e., emotional, social, and self-regulated learning) in a sample of university students using a person-centred approach. Results from a two-cohort sample (N = 1650) assessed at the beginning of their first year supported a 4-cluster solution: 1) Highly Self-Efficacious students, with high levels of self-efficacy in all domains; 2) Low Self-Efficacious students, with low levels of self-efficacy in all domains; 3) Learning and Socially Self-Efficacious students, with a medium-high level of self-regulated learning, medium level of social, and medium-low level of emotional self-efficacies; and 4) Emotionally Self-Efficacious students, with a medium-high level of emotional, medium-low level of social, and low level of self-regulated learning self-efficacies. The association of these configurations with wellbeing indicators, concurrently and one year later, provides support for the validity of the cluster solution. Specifically, by adopting the informative hypothesis testing approach, results showed that the first and second groups have the best and the worst wellbeing levels, respectively. Furthermore, whereas the other two groups did not differ with respect to depression, Learning and Socially Self-Efficacious students have higher life satisfaction than the last group. These results were confirmed both concurrently and over time
The implicit component of moral disengagement: applying the relational responding task to investigate its relationship with cheating behavior
This article aims to conceptualize, for the first time, an implicit form of moral disengagement and investigate its role in relation to cheating behavior. In line with the implicit social-cognition models, we argue that the implicit moral disengagement would represent an unintentional, automatic, and less accessible form of the mechanisms bypassing the moral self-regulatory system. We anticipate that in situations implying on-the-spot decisions and where individuals might suffer no consequences for the misconduct, the implicit moral disengagement would predict the actual behavior while the explicit moral disengagement would predict self-reported conduct. The results of three empirical studies provide support for the theorization of an implicit moral disengagement and its assessment through a newly developed implicit measurement procedure using the relational responding task. Results of the structural equation models, including both implicit and explicit moral disengagement, demonstrated that only the implicit one was associated with the actual misconduct
'First, do no harm': the role of negative emotions and moral disengagement in understanding the relationship between workplace aggression and misbehavior
Workplace aggression is a critical phenomenon particularly in the healthcare sector, where nurses are especially at risk of bullying and third-party aggression. While workplace aggression has been frequently examined in relation to health problems, less is known about the possible negative impact such aggression may have on the (un)ethical behavior of victims. Our research aims to fill this gap. Drawing on literature on counterproductive work behavior (CWB) and the social-cognitive literature on aggression we investigated in two independent studies (NStudy1 = 439; NStudy2 = 416), the role of negative emotions - in particular anger, fear, and sadness, - and of moral disengagement (MD) in the paths between workplace aggression, CWB and health symptoms. The focus on these relationships is rooted in two reasons. First, misbehavior at work is a pervasive phenomenon worldwide and second, little research has been conducted in the healthcare sector on this type of behavior despite the potential importance of the issue in this context. We empirically tested our hypotheses considering a specific form of workplace aggression in each study: workplace bullying or third-party aggression. Results from the two empirical studies confirm the hypotheses that being target of workplace aggression (bullying or third-party aggression) is not only associated with health symptoms but also with misbehavior. In addition, the results of structural equation modeling attest the importance of examining specific discrete negative emotions and MD for better understanding misbehavior at work. In particular, this research shows for the first time that anger, fear, and sadness, generally aggregated into a single dimension, are indeed differently associated with MD, misbehavior and health symptoms. Specifically, in line with the literature on discrete emotions, while sadness is only associated with health symptoms, anger and fear are related to both health and misbehavior
Non-Perturbative Renormalisation of Composite Operators
It is shown that the renormalisation constants of two quark operators can be
accurately determined (to a precision of a few per-cent using 18 gluon
configurations) using Chiral Ward identities. A method for computing
renormalisation constants of generic composite operators without the use of
lattice perturbation theory is proposed.Comment: 3 pages, uuencoded compressed postscript file, to appear in the
Proceedings of the International Symposium on Lattice Field Theory, Dallas,
Texas, 12-17 October 1993, Southampton Preprint 93/94-0
A Lattice Study of the Gluon Propagator in Momentum Space
We consider pure glue QCD at beta=5.7, beta=6.0 and beta=6.3. We evaluate the
gluon propagator both in time at zero 3-momentum and in momentum space. From
the former quantity we obtain evidence for a dynamically generated effective
mass, which at beta=6.0 and beta=6.3 increases with the time separation of the
sources, in agreement with earlier results. The momentum space propagator G(k)
provides further evidence for mass generation. In particular, at beta=6.0, for
k less than 1 GeV, the propagator G(k) can be fit to a continuum formula
proposed by Gribov and others, which contains a mass scale b, presumably
related to the hadronization mass scale. For higher momenta Gribov's model no
longer provides a good fit, as G(k) tends rather to follow an inverse power
law. The results at beta=6.3 are consistent with those at beta=6.0, but only
the high momentum region is accessible on this lattice. We find b in the range
of three to four hundred MeV and the exponent of the inverse power law about
2.7. On the other hand, at beta=5.7 (where we can only study momenta up to 1
GeV) G(k) is best fit to a simple massive boson propagator with mass m. We
argue that such a discrepancy may be related to a lack of scaling for low
momenta at beta=5.7. {}From our results, the study of correlation functions in
momentum space looks promising, especially because the data points in Fourier
space turn out to be much less correlated than in real space.Comment: 19 pages + 12 uuencoded PostScript picture
Crashworthiness of a composite bladder fuel tank for a tilt rotor aircraft
The fulfilment of the crash is a demanding requirement for a Tiltrotor. Indeed, such a kind of aircraft, being a hybrid between an airplane and a helicopter, inherits the requirements mainly from helicopters (EASA CS 29) due to its hovering ability. In particular, the fuel storage system must be designed in such a manner that it is crash resistant, under prescribed airworthiness requirements, in order to avoid the fuel leakage during such an event, preventing fire and, thus, increasing the survival chances of the crew and the passengers. The present work deals with the evaluation of crashworthiness of the fuel storage system of a Tiltrotor (bladder tank), and, in particular, it aims at describing the adopted numerical approach and some specific results. Crash resistance requirements are considered from the earliest design stages, and for this reason they are mainly addressed from a numerical point of view and by simulations that treat both single components and small/medium size assemblies. The developed numerical models include all the main parts needed for simulating the structural behavior of the investigated wing section: the tank, the structural components of the wing, the fuel sub-systems (fuel lines, probes, etc.) and the fuel itself. During the crash event there are several parts inside the tanks that can come into contact with the tank structure; therefore, it is necessary to evaluate which of these parts can be a damage source for the tank itself and could generate fuel loss. The SPH approach has been adopted to discretise fuel and to estimate the interaction forces with respect to the tank structure. Experimental data were used to calibrate the fuel tank and foam material models and to define the acceleration time-history to be applied. Thanks to the optimized foam’s configuration, the amount of dissipated impact energy is remarkable, and the evaluation of tanks/fuel system stress distribution allows estimating any undesired failure due to a survivable crash event
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