A Petri Nets Model for Blockchain Analysis

A Blockchain is a global shared infrastructure where cryptocurrency transactions among addresses are recorded, validated and made publicly available in a peer- to-peer network. To date the best known and important cryptocurrency is the bitcoin. In this paper we focus on this cryptocurrency and in particular on the modeling of the Bitcoin Blockchain by using the Petri Nets formalism. The proposed model allows us to quickly collect information about identities owning Bitcoin addresses and to recover measures and statistics on the Bitcoin network. By exploiting algebraic formalism, we reconstructed an Entities network associated to Blockchain transactions gathering together Bitcoin addresses into the single entity holding permits to manage Bitcoins held by those addresses. The model allows also to identify a set of behaviours typical of Bitcoin owners, like that of using an address only once, and to reconstruct chains for this behaviour together with the rate of firing. Our model is highly flexible and can easily be adapted to include different features of the Bitcoin crypto-currency system

Risk Perception and COVID-19 During Lockdown: Evidence from an Italian Sample

This paper investigates how a specific extraordinary event such as the COVID-19 pandemic is perceived among individuals. Upsetting the taken-for-granted practices of people’s everyday life, the pandemic caused negative emotional responses, mainly the feeling of concern about its aftermath on health and social and economic aspects. However, these responses are not equally spread among social groups. Some of them are more associated with states of panic and anxiety, according to their socially defined and transmitted roles and identities. This paper focuses on a specific element of the perception of the COVID-19 pandemic, i.e. risk, based on a survey conducted in Italy (N = 1,704) during the last three weeks of lockdown (26th of April 2020 – 17th of May 2020). The analyses aim to detect patterns in socio-demographic variables in COVID-19 risk perception in the Italian population during lockdown, also accounting for their variation over time. In fact, the analyses suggest that approaching and being aware of the loosening of lockdown measures (18th of May 2020) may have decreased the perceived risk. Results prove consistent with findings from previous research

Monitoraggio dei flussi migratori nel Mar Mediterraneo con satelliti ottici e SAR

Il Mediterraneo è sempre stato considerato un’area di intensi scambi politici, economici e culturali, ma nell’ultimo decennio è diventato anche luogo di intensi flussi migratori dal Nordafrica verso l’Europa. L’immigrazione illegale via mare ha ormai assunto una dimensione tale che nei soli primi due mesi del 2016 oltre 110.000 migranti hanno attraversato il Mediterraneo (fonte: UNHCR). Alla luce di questi numeri, in continua crescita, le istituzioni europee stanno cercando nuove soluzioni per rafforzare il monitoraggio dei confini esterni dell’Unione Europea. Tale operazione, che coinvolge un’area geografica molto estesa, risulta però complessa e costosa se svolta solamente con i mezzi tradizionali (radar di terra, mezzi aerei e navali). In questo contesto, il progetto Space Shepherd cofinanziato dal Politecnico di Milano nell’ambito del programma Polisocial Award, si è occupato dello studio di fattibilità di un sistema integrato ottico-radar per l’individuazione, il monitoraggio e il tracciamento d’imbarcazioni sconosciute in navigazione nel Mar Mediterraneo utilizzando asset speziali già esistenti (Topputo et al., 2015b). L’utilizzo congiunto d’immagini ottiche e radar è in grado di garantire un’osservazione continua e non dipendente dalle condizioni atmosferiche o di illuminazione e una complementarietà in termini di copertura geografica e dettaglio geometrico

Percezione, motivazione, esistenza. Intenzionalità e costituzione nella prima fenomenologia husserliana (1898-1921)

The present work is a systematic study of the nexus which holds together perception, motivation and existence in Husserl’s early writings—precisely those which are dated between 1898 and 1921. In Chapter I a historical and conceptual reconstruction of the genesis of what is termed ‘constitution problem’ is provided. After a thorough discussion about the distinction between real and intentional description, we elucidate the method of phenomenological reduction and show how the constitution problem relates to questions regarding transcendence and existence. Chapter II is concerned with a detailed presentation of Husserlian phenomenology of visual perception. We present Husserl’s theory of intentionality in the light of Husserlian mereology: first, we argue that Husserl conceives of intentionality as a property which entails a relation; secondly, we debate his critique of the theory of immanent objects and his solution to the problem of non-existent objects. After examining the perceptual act in all its essential components (i.e. quality, matter and sensations), we discuss the notorious ‘content – apprehension’ schema and study the manuscripts in which Husserl develops the notion of ‘perceptional’. Themes like the relationship between fulfillment and disappointment and the distinguishability of veridical and non-veridical perceptions are also taken into account. In Chapter III we consider what differentiates the outer perception from other kinds of perception. After making clear what Husserl means by ‘inner perception’ we debate the opposition between immanent and transcendent perception, first by using identity/manifold analysis and then by means of whole/part analysis. In this context we reject Husserl’s account of reflection as a perceptual act on both exegetical and theoretical grounds. Furthermore, we explain how Husserl tries to refute the ‘image theory’ and how he addresses the issue of the hidden profiles. The study of the microstructure of the outer perception allows us to explain in which sense this kind of perception is to be conceived as necessarily inadequate. Chapter IV is largely devoted to an attempt at systematizing Husserl’s theory of kinaesthesia as it appears in the Dingvorlesung. This sheds light on the structure of motivation and on the role which this latter plays in the constitution of a mundane object. In Chapter V we scrutinize Husserl’s conception of the possibility/reality dichotomy. In particular, we distinguish an ontological analysis of possibility from a phenomenological one and investigate the diverse concepts of ‘possibility’ (e.g. ideal, real, independent, modal) developed by Husserl. Finally, we introduce and debate Husserl’s (so-called) ‘exhibition principle’ and try to point out its ambiguities

A Radical Relationist Solution to the Problem of Intentional Inexistence

The problem of intentional inexistence arises because the following (alleged) intuitions are mutually conflicting: it seems that sometimes we think about things that do not exist; it seems that intentionality is a relation between a thinker and what such a thinker thinks about; it seems that relations entail the existence of what they relate. In this paper, I argue for what I call a radical relationist solution. First, I contend that the extant arguments for the view that relations entail the existence of their relata are wanting. In this regard, I defend a kind of pluralism about relations according to which more than one kind of relation involves non-existents. Second, I contend that there are reasons to maintain that all thoughts are relations between thinkers and the things they are about. More accurately, I contend that the radical relationist solution is to be preferred to both the intentional content solution (as developed by Crane) and the adverbial property solution (as developed by Kriegel). Finally, I argue that once the distinction between thinking “X” and thinking about X has been drawn, the radical relationist solution can handle issues like ontological commitment, substitutivity failure, scrutability, and non-specificity