Novel Network Paradigms: Microfluidic and M2M Communications

The present thesis focuses on two appealing paradigms that are expected to characterize the next generation of communication systems: microfluidic networking and Machine to Machine (M2M) Communications. Concerning the former topic, we show how it is possible to introduce switching and routing mechanism in microfluidic systems. We define some simple mathematical models that capture the macroscopic behavior of droplets in microfluidic networks. Then, we use them to implement a simulator that is able to reproduce the motion and predict the path of droplets in a generic microfluidic system. We validate the simulator and apply it to design a network with bus topology. Finally, we prove the feasibility of attaining molecular communication in this domain by describing a simple protocol that exploits droplets length/interdistance modulation to send information. The research activity on M2M, instead, is aimed at the investigation of two critical issues that are expected to affect Machine-Type Communication (MTC), i.e. energy efficiency and massive access. Regarding energy efficiency, we address the problem of delivering a fixed data payload over a Rayleigh fading wireless channel with the purpose of minimizing the average total energy cost, given by the sum of the transmit energy and an overhead circuit energy, to complete it. This scenario is well suited for uplink cellular MTC in future 5G Internet of Things (IoT) use cases, where the focus is more on device energy efficiency than on throughput. We describe the optimal transmission policies to be used under various coordinated access scenarios with different levels of channel state information and transmitter/receiver capabilities, and show the corresponding theoretical bounds. In the last part of the work, we study the asymptotic performance of uncoordinated access schemes with Multi Packet Reception (MPR) and Successive Interference Cancellation (SIC) techniques for contention resolution at the receiver. The corresponding results in terms of throughput in a massive access M2M scenario are finally evaluated and discussed

Transport collapse in dynamically evolving networks

Transport in complex networks can describe a variety of natural and human-engineered processes including biological, societal and technological ones. However, how the properties of the source and drain nodes can affect transport subject to random failures, attacks or maintenance optimization in the network remain unknown. In this paper, the effects of both the distance between the source and drain nodes and of the degree of the source node on the time of transport collapse are studied in scale-free and lattice-based transport networks. These effects are numerically evaluated for two strategies, which employ either transport-based or random link removal. Scale-free networks with small distances are found to result in larger times of collapse. In lattice-based networks, both the dimension and boundary conditions are shown to have a major effect on the time of collapse. We also show that adding a direct link between the source and the drain increases the robustness of scale-free networks when subject to random link removals. Interestingly, the distribution of the times of collapse is then similar to the one of lattice-based networks

Predicting collapse of adaptive networked systems without knowing the network

The collapse of ecosystems, the extinction of species, and the breakdown of economic and financial networks usually hinges on topological properties of the underlying networks, such as the existence of self-sustaining (or autocatalytic) feedback cycles. Such collapses can be understood as a massive change of network topology, usually accompanied by the extinction of a macroscopic fraction of nodes and links. It is often related to the breakdown of the last relevant directed catalytic cycle within a dynamical system. Without detailed structural information it seems impossible to state, whether a network is robust or if it is likely to collapse in the near future. Here we show that it is nevertheless possible to predict collapse for a large class of systems that are governed by a linear (or linearized) dynamics. To compute the corresponding early warning signal, we require only non-structural information about the nodes’ states such as species abundances in ecosystems, or company revenues in economic networks. It is shown that the existence of a single directed cycle in the network can be detected by a “quantization effect” of node states, that exists as a direct consequence of a corollary of the Perron–Frobenius theorem. The proposed early warning signal for the collapse of networked systems captures their structural instability without relying on structural information. We illustrate the validity of the approach in a transparent model of co-evolutionary ecosystems and show this quantization in systems of species evolution, epidemiology, and population dynamics

Citizenship Laws and International Migration in Historical Perspective

We investigate the origin, impact and evolution of citizenship laws. Citizenship laws originate from the common and civil law traditions, which apply jus soli and jus sanguinis, respectively. We compile a data set across countries of the world starting from the 19th century. The impact of the original, exogenously-given laws on international migration proves insignificant for the early, mass migration waves, which confirm to be driven primarily by economic incentives. Postwar convergence of citizenship laws is determined by legal tradition and international migration, but also by border stability, the establishment of democracy, the welfare burden, cultural factors and colonial history.Citizenship laws, International migration, Legal origins, Democracy, Borders

Teacher and Student Perspectives on Songwriting Pedagogy in Middle School

A song is a form of musical composition that involves a marriage between words and melody. In music education, songwriting often belongs to the sphere of popular music. Although songs are omnipresent in adolescents’ lives, less than 7% of the secondary schools in the United States offer songwriting. The present study focused on an after-school songwriting course in a middle school in the Southern U.S., a 21st-century learning environment where music and technology walked hand in hand, and adolescents composed, produced, and distributed original songs while finding their voices as songwriters. Five broad interrelated themes emerged from the literature review: songwriting is a place for inclusion, a music technology laboratory, it does not need traditional music notation, the teacher as facilitator, and conceptual teaching. The purpose of this study was to explore middle school songwriting pedagogy, how the teacher designed, implemented, and evaluated the songwriting course, and the students’ perspectives on their experiences. Ethnographic methods of data collection were employed, comprising interviews, field notes and participant observation, documents, and creative writing as research. Thematic and structural narrative analytical approaches suggested that teachers succeeded in forging a 21st-century popular music laboratory where students pursued their interests facilitated by a safe and collaborative environment in which teacher and peer feedback enriched trial-and-error in sound. Teachers’ strategies ranged from modeling to fading and the formulation of scaffolding where students interacted with music technology in a recording studio the size of their hands, resituating play at the center of music-making. Consequently, students learned from eliminating their mistakes and solving real-world musical problems that emerged from and within the processual products of their songwriting. The teacher described her pedagogic approach as focused on constant feedback, modeling, and scaffolding toward small projects that strengthened students’ musicianship. In her view, songwriting was personal. In addition, it offered the opportunity to pull students into large ensembles. Students expressed ease in using Digital Audio Workstations (DAWs) on tablet-based devices to facilitate music participation since most did not play a musical instrument. They believed songwriting enabled them to learn to collaborate, take risks, and improve their musical skills through constructive feedback

AN EXPLORATORY STUDY OF INTIMATE RELATIONSHIP SOCIALIZATION AMONG BLACK COLLEGIATE WOMEN

The pathways through which individuals learn to appraise and behave in intimate relationships greatly influence the quality and stability of their relationships. Research on intimate relationships among college students guided by a socialization framework focusing on learning and ways of viewing relationships is limited. The purpose of the present exploratory study was to examine the experiences and processes wherein young Black collegiate women learn to approach, maintain, and reflect on their intimate relationships. This topic is particularly salient to Black collegiate women who find themselves navigating unbalanced dating scenes and negotiating love relationships while balancing academic achievement and career aspirations. Ten Black, heterosexual women attending a four-year institution of higher education participated in three in-depth interviews where they shared life experiences which contributed to their understanding of intimate relationships. Using symbolic interactionism as a guiding framework allowed me to discover the multiple descriptions and meanings the participants assign to the interactions in their families, with their peers, and in their symbolic environments. The narratives shared by the women in this study revealed a number of experiences which prompted them to engage in self-reflection, critique, and learning with respect to self-identity and intimate relationships. Hearing messages, observing others, and experiencing relationships for themselves provided these women with a foundation for knowing the importance of preserving self-worth and self-identity, establishing expectations, and communicating thoughts and feelings. Implications for practice include the importance of developing specialized relationship education culturally and socially relevant to Black collegiate women, training campus professionals on the unique needs and concerns of this population, and educating parents on communicating with daughters about intimate relationship development. Future research should devote specific attention to social context, paternal-daughter relationship communication, and parental relationship modeling