Noise and delays in adaptive interacting oscillatory systems

Rodriguez J. Noise and delays in adaptive interacting oscillatory systems. Bielefeld: Universitätsbibliothek; 2013.In this thesis, we explore the global behavior of complex systems composed of interacting local dynamical systems, each set on a vertex of a network which characterizes the mutual interactions. We consider heterogeneous arrangements, meaning that for each vertex the local dynamics can be different. To better match potential applications we allow mutual interactions to be time delayed and subject to noise sources affecting either the orbits of the local dynamics and/or the connectivity of the network. Within this very general dynamical context, we construct and focus on interactions enabling a certain level of adaptation between the local dynamical systems. By propagation of information via the coupling network, the local parameters are adaptively tuned and ultimately reach a set of consensual values. This is explicitly and analytically carried out for frequency- and radius-adapting HOPF oscillators. We then consider adapting the time scale and the shape of periodic signals. We also study how adaptive mechanisms can be implemented in heterogeneous networks formed by a couple of subnetworks, the first one with adaptive capability and the second one without. The first subnetwork defines interactions between phase oscillators with adaptive frequency capability, the other subnetwork connects damped vibrating systems without adaptation. Next, noise sources are introduced into the dynamics via stochastic switchings of the network connections. This extra time-dependence in the network opens the possibility for parametric resonance and destabilization of a consensual oscillatory state, found for purely static networks. Finally, we introduce external noise environments which corrupt the orbits of the local systems. For ''All-to-All'' network topology, we analytically derive the effects of Gaussian and non-Gaussian noise sources and unveil noise induced emergent oscillating patterns of the relevant order parameter that characterizes this dynamics. Although in this thesis the emphasis is made on deriving analytical results, we systematically supplement our findings with extensive numerical simulations. They not only corroborate and illustrate our theoretical assertions but provide additional insights where analytical results could not be found

Galapagos farmers: risk and the coexistential rift

Galapagos farmers are generally invisible in global discourses and remain understudied from an anthropological perspective. Drawing on a year of ethnographic fieldwork during the 2020-2021 global pandemic, this thesis focuses on their main worries and livelihood challenges. The liminal period created during the Covid-19 pandemic brought back many aspects of life prior to the arrival of the archipelago’s tourism industry and led farmers to yearn for a nostalgic, utopian past when they coexisted more harmoniously with each other and the environment. Unfortunately, many elements of that idealized life are currently unattainable due to compounding risks, including pests, climate change, and Covid-19. The everyday threats to farmers’ livelihoods have led to market dependence, indebtedness, alienation, and cumulative anxiety. I explore each risk ethnographically, whilst also showing the ways in which they are part of a causal framework that alters farmers’ values and behaviours. This thesis formulates the coexistential rift concept to explain how both the materiality of risks and their perception accelerate a treadmill syndrome where farmers must focus on making money to lessen their insecurity. This vicious cycle is reinforced by the slow violence of political abandonment, economic inequality, fortress conservation, legal and bureaucratic obstacles, and predominant metanarratives that blame and exclude the archipelago’s inhabitants. Both Galapagueño society and the environment would benefit from addressing the agricultural sector’s long-standing problems. Finally, this thesis points to how human and political ecological studies can better conceptualize and incorporate risks into their analysis and causal frameworks to elucidate their impact on everyday life

Ferroelectric Tunnel Junctions

Ferroelectricity and quantum-mechanical electron tunneling are well-known physical phenomena that have been studied for as long as a century. During this long period, scientific research has been restricted either to ferroelectricity or to electron tunneling. Never before have these subjects been combined into a new phenomenon based on their interaction. Within this work, I present the novel concept of a ferroelectric tunnel junction, where the term ferroelectric refers to a property of the barrier material. This device consists of a ferroelectric layer sandwiched between metal electrodes. The thickness of the ferroelectric layer is thin enough to allow for electron tunneling. For the first time, the influence of macroscopic parameters, such as the spontaneous polarization and strain on quantum-mechanical electron tunneling through a ferroelectric tunnel barrier is studied experimentally. In addition, the experimental work is accompanied by theoretical ideas and predictions concerning the manifestation of piezoelectricity or ferroelectricity in direct electron tunneling

Public Servants\u27 Perceptions of the Cybersecurity Posture of the Local Government in Puerto Rico

The absence of legislation, the lack of a standard cybersecurity framework, and the failure to adopt a resilient cybersecurity posture can be detrimental to the availability, confidentiality, and integrity of municipal information systems. The purpose of this phenomenological study was to understand the cybersecurity posture of municipalities from the perception of public servants serving in information technology (IT) leadership roles in highly populated municipalities in the San Juan-Carolina-Caguas Metropolitan Statistical Area of Puerto Rico. The study was also used to address key factors influencing the cybersecurity posture of these municipalities. The theoretical framework was open system theory used in combination with a conceptual framework encompassing key dimensions influencing digital government. Data were collected using semistructured interviews with 10 public servants working in IT leadership positions in a municipal setting in Puerto Rico. Data analysis involved horizontalization, reduction, elimination, clustering, thematizing, validation, and development of individual and composite textural descriptions. Participants reported that the cybersecurity posture of their municipalities was resilient. Participants also reported that technological changes, politics, the economy, management support, and processes were key elements to achieve a resilient posture. Findings may be used to empower elected officials, policymakers, public servants, and practitioners to manage and improve elements affecting cybersecurity with the goal of achieving a resilient posture to deliver cybersecurity as a public good

The Determinants of Soccer Player Substitutions: a Survival Analysis of the Spanish Soccer League

This paper analyzes the pattern of player substitutions during a soccer match, using data from the First Division (Primera División) of the Spanish National Soccer League in the 2004-2005 season. To do so, an inverse Gaussian hazard model is adopted to analyze the first substitutions of each team that take place at half-time and in the second half of matches. The results show that the most important factor is the score as it stands prior to the time of the player substitution. Furthermore, defensive substitutions are made later in the match than offensive substitutions. We also find some evidence that the home team makes more substitutions than the visiting team in the halftime interval.hazard model; soccer substitutions; strategy.

An explorative study of socioeconomic characteristics and needs of Hispanic parents of children with special needs in one western Massachusetts school district.

This study describes the socioeconomic characteristics, assesses the basic information about special education the Hispanic parents are interested in knowing about through educational workshops and orientation, and identifies the need for services that allow the Hispanic parents active participation in the educational processes of their children with special needs. The involvement of parents in the education of their children with special needs at the national level was mandated by Public Law 94-142, The Education of All Handicapped Children Act of 1975. According to this Federal Law, the parents have the right to be active participants in decision making related to the educational needs of their children, especially in the development of the Individualized Educational Plan (IEP). According to the literature reviewed, parents are usually less prepared to actively participate in IEP conferences since they possess the least amount of knowledge pertaining to laws, advocacy, rights, sources, and special education procedures. Studies have demonstrated that participation of parents in the decision-making process has been passive, limited to giving and receiving information, and sometimes simply signing the Individualized Educational Plan (IEP). The lack of knowledge about Public Law 94-142 and about the procedures of special education related to services makes necessary the creation of educational workshops addressed to parents of children with special needs. In the first part of this study, it was found that Hispanic parents surveyed in the site selected for this research study show particular socioeconomic characteristics that should be taken into consideration when active participation and involvement in the educational process of their children with special needs is expected. Findings in the second and third part of this study should be taken into consideration by school personnel, administrators, and community-based program directors when planning, developing, and providing educational workshops, counseling, and orientation to a culturally-diverse population

Networks of Self-Adaptive Dynamical Systems

We discuss the adaptive behaviour of a collection of heterogeneous dynamical systems interacting via a weighted network. At each vertex, the network is endowed with a dynamical system with individual (initially different) control parameters governing the local dynamics. We then implement a class of network interactions which generates a self-adaptive behaviour, driving all local dynamics to adopt a set of consensual values for their local parameters. While for ordinary synchronization each individual dynamical system is restored to its original dynamics once network interactions are removed, here the consensual values of control parameters are definitively acquired—even if interactions are removed. For a wide class of dynamical systems, we show analytically how such a plastic and self-adaptive training of control parameters can be realized. We base our study on local dynamics characterized by dissipative ortho-gradient vector fields encompassing a vast class of attractors (in particular limit cycles). The forces generated by the coupling network are derived from a generalized potential. A set of numerical experiments enables us to observe the transient dynamics and corroborate the analytical results obtaine