1,957 research outputs found
Contraction analysis of nonlinear systems and its application
The thesis addresses various issues concerning the convergence properties of switched systems and differential algebraic equation (DAE) systems. Specifically, we focus on contraction analysis problem, as well as tackling problems related to stabilization and synchronization. We consider the contraction analysis of switched systems and DAE systems. To address this, a transformation is employed to convert the contraction analysis problem into a stabilization analysis problem. This transformation involves the introduction of virtual systems, which exhibit a strong connection with the Jacobian matrix of the vector field. Analyzing these systems poses a significant challenge due to the distinctive structure of their Jacobian matrices. Regarding the switched systems, a time-dependent switching law is established to guarantee uniform global exponential stability (UGES). As for the DAE system, we begin by embedding it into an ODE system. Subsequently, the UGES property is ensured by analyzing its matrix measure. As our first application, we utilize our approach to stabilize time-invariant switched systems and time-invariant DAE systems, respectively. This involves designing control laws to achieve system contractivity, thereby ensuring that the trajectory set encompasses the equilibrium point. In oursecond application, we propose the design of a time-varying observer by treating the system’s output as an algebraic equation of the DAE system. In our study on synchronization problems, we investigate two types of synchronization issues: the trajectory tracking of switched oscillators and the pinning state synchronization. In the case of switched oscillators, we devise a time-dependent switching law to ensure that these oscillators effectively follow the trajectory of a time-varying system. As for the pinning synchronization problem, we define solvable conditions and, building upon these conditions, we utilize contraction theory to design dynamic controllers that guarantee synchronization is achieved among the agents
Contraction analysis of nonlinear systems and its application
The thesis addresses various issues concerning the convergence properties of switched systems and differential algebraic equation (DAE) systems. Specifically, we focus on contraction analysis problem, as well as tackling problems related to stabilization and synchronization. We consider the contraction analysis of switched systems and DAE systems. To address this, a transformation is employed to convert the contraction analysis problem into a stabilization analysis problem. This transformation involves the introduction of virtual systems, which exhibit a strong connection with the Jacobian matrix of the vector field. Analyzing these systems poses a significant challenge due to the distinctive structure of their Jacobian matrices. Regarding the switched systems, a time-dependent switching law is established to guarantee uniform global exponential stability (UGES). As for the DAE system, we begin by embedding it into an ODE system. Subsequently, the UGES property is ensured by analyzing its matrix measure. As our first application, we utilize our approach to stabilize time-invariant switched systems and time-invariant DAE systems, respectively. This involves designing control laws to achieve system contractivity, thereby ensuring that the trajectory set encompasses the equilibrium point. In oursecond application, we propose the design of a time-varying observer by treating the system’s output as an algebraic equation of the DAE system. In our study on synchronization problems, we investigate two types of synchronization issues: the trajectory tracking of switched oscillators and the pinning state synchronization. In the case of switched oscillators, we devise a time-dependent switching law to ensure that these oscillators effectively follow the trajectory of a time-varying system. As for the pinning synchronization problem, we define solvable conditions and, building upon these conditions, we utilize contraction theory to design dynamic controllers that guarantee synchronization is achieved among the agents
Multidisciplinary perspectives on Artificial Intelligence and the law
This open access book presents an interdisciplinary, multi-authored, edited collection of chapters on Artificial Intelligence (‘AI’) and the Law. AI technology has come to play a central role in the modern data economy. Through a combination of increased computing power, the growing availability of data and the advancement of algorithms, AI has now become an umbrella term for some of the most transformational technological breakthroughs of this age. The importance of AI stems from both the opportunities that it offers and the challenges that it entails. While AI applications hold the promise of economic growth and efficiency gains, they also create significant risks and uncertainty. The potential and perils of AI have thus come to dominate modern discussions of technology and ethics – and although AI was initially allowed to largely develop without guidelines or rules, few would deny that the law is set to play a fundamental role in shaping the future of AI. As the debate over AI is far from over, the need for rigorous analysis has never been greater. This book thus brings together contributors from different fields and backgrounds to explore how the law might provide answers to some of the most pressing questions raised by AI. An outcome of the Católica Research Centre for the Future of Law and its interdisciplinary working group on Law and Artificial Intelligence, it includes contributions by leading scholars in the fields of technology, ethics and the law.info:eu-repo/semantics/publishedVersio
Towards a General Complex Systems Model of Economic Sanctions with Some Results Outlining Consequences of Sanctions on the Russian Economy and the World
The main purpose of this paper is to present a complex nonlinear modelling approach to analyzing mixed capitalist economic systems. An application of a more elaborate version of this model is to explore the consequences of sanctions on the Russian economy and evaluate the model’s predictive successes or failures. Furthermore, the formal expanded nonlinear model presented in the appendix may be seen as an initial step to put the analysis of economic sanctions within a formal complex socio-economic systems framework. The results obtained from this structural complex multisectoral model so far seem fairly accurate in terms of agreement with measured values of observable economic variables. The political consequences are uncertain and are to be explored separately in a companion paper and ultimately in a book length treatment.
Methodologically, the paper also presents the case for using Social Accounting Matrix (SAM)-based models for understanding problems of analyzing sanctions in an economywide context. Linear as well as Nonlinear models are presented in the appendix. The nonlinear modelling approach might prove to be especially relevant for studying the properties of multiple equilibria and complex dynamics
Essays in the economics and econometrics of networks and peer effect
Defence date: 23 May 2023Examining Board: Prof. Andrea Ichino, (European University Institute, supervisor); Prof. Sule Alan, (European University Institute, co-supervisor); Prof. Eric Auerbach, (Northwestern University); Prof. Yann Bramoullé, (Aix-Marseille School of Economics)This thesis contributes to the understanding of peer effects, both methodologically and empirically. The endogeneity of network formation has been a major obstacle to the study of peer influence. The first and the second chapters of the thesis propose a causal identification solution in the potential outcome framework. Combining results from multiple causal inference and statistical network analysis, I show that confounding can be addressed by inferring propensity scores of network link formation from the adjacency matrix. This identification strategy imposes minimum restrictions on the data-generating process and, unlike existing econometric solutions, does not rely on any parametric modelling. As an application, I estimate the effect of high school friendships on bachelor’s degree attainment. While previous literature finds that exposure to more high-achieving boys makes girls less likely to obtain a bachelor’s degree, I show that if the girls consider the boys as friends, their interactions induce a positive impact instead. Since friendship endogeneity has been addressed, the estimated effect is causal. The third chapter looks at the peer effects generated by group competition. It focuses on the gender differences in preference for competition in a setting where the competition does not involve face-to-face confrontation, and effort is the only determinant of the final ranking. I first develop a model of group competition with heterogeneous preference for ranking. With empirical implications generated from the theoretical model, I then test the gender difference in the preference parameter using web-scraped data from Duolingo, a free online foreign-language learning platform with over 300 million users. Every week, language learners on Duolingo are randomly allocated to groups of 30 people to compete on the number of language lessons completed during that week. The empirical results suggest in this setting, females have a stronger preference for ranking than males.1. The linking effect: causal identification and estimation of the effect of peer relationship --
2. Extensions, theoretical proofs, and additional results on the linking effect --
3. Gender difference in preference for competition --
4. Reference
Essays on behavioural economics: Uncovering drivers of altruistic behaviour
This Ph.D. thesis aims to study the economic foundations of prosocial behaviour in multiple significant ways. First, it emphases that altruistic behaviour can be the result of individual differences in people when using survey experiments, but also in nations when analysing information at an aggregate level. Second, it also states that altruism appears more prominently when more options are given for decision-makers to choose among alternatives to donate. For that purpose, I present a broad literature review and four empirical essays that provide new evidence on these particular topics. The first essay makes an overall analysis on altruism at a global scale using a database from The World Bank and The World Happiness report for the period 2020. The empirical analysis is conducted using cross-sectional country data from a sample of 128 worldwide countries in the 6 continents. The results suggest that nations which exhibit higher generosity levels are also quite distinct from the others, such as in the level of economic development, in some socio-demographic variables and cultural dimensions. The other three essays are based on the collection of experimental survey data aiming at identifying new factors that may explain generous behaviour in individuals. Specifically, the second tries to stablish a relationship between free will beliefs and giving, the third relates cognitive skills with strategic thinking abilities and the last one studies how the number of options available affects giving. The results suggest that higher free will beliefs have a statistically significant effect on generous concerns. Personal cognitive skills and strategic thinking abilities also have a relationship with giving. However, the former has a negative influence while the latter is positive. Finally, in the last essay, I observe that generosity increases when more recipient options are available and this effect is statistically significant, as well. This thesis contributes to our understanding of prosocial behaviour in terms of individual and country characteristics that are correlated with altruistic behaviour.Esta tese de doutoramento visa estudar as bases económicas do comportamento pro-social de várias formas distintas: Em primeiro lugar, enfatiza que o comportamento altruÃsta pode ser o resultado de diferenças individuais em seres humanos, quando se recolhem dados através de inquéritos, mas também em paÃses, quando se analisa informação a um nÃvel agregado. Em segundo lugar, demonstra que o comportamento altruÃsta emerge de uma forma mais notória quando são dadas mais opções à s pessoas para escolherem entre alternativas para doar. Para o efeito, apresento uma revisão da literatura generalizada e quatro ensaios empÃricos que sugerem novas evidências sobre estes tópicos, em particular. O primeiro ensaio faz uma análise sobre o altruÃsmo à escala global utilizando dados do Banco Mundial e do relatório The World Happiness Report referente ao perÃodo de 2020. A análise empÃrica é conduzida utilizando dados de uma amostra de 128 paÃses em 6 continentes. Os resultados sugerem que as nações que apresentam nÃveis de generosidade mais elevados são também bastante distintas em relação à s restantes, nomeadamente ao nÃvel do desenvolvimento económico, na vertente sociodemográfica e ainda culturalmente. Os outros três ensaios baseiam-se na recolha de dados através de inquéritos com o objetivo de identificar novos fatores que possam explicar o comportamento pro-social em indivÃduos. Especificamente, o segundo tenta estabelecer uma relação entre crenças no livre-arbÃtrio e generosidade, o terceiro com capacidades cognitivas/estratégicas e o último com o número de opções disponÃveis para doação. Os resultados sugerem que as pessoas que possuem crenças mais robustas no livre-arbÃtrio revelam também ter maiores tendências generosas. Os resultados sugerem ainda que as competências cognitivas e as capacidades de pensamento estratégico têm também uma relação com o altruÃsmo. No entanto, o primeiro fator tem uma influência negativa enquanto o segundo positiva. Finalmente, no último ensaio, foi observado que a
generosidade aumenta quando estão disponÃveis mais opções para doar. Globalmente, esta tese contribui para aumentar a nossa compreensão do comportamento pro-social em termos das caracterÃsticas individuais que lhe estão correlacionadas
Collective agency:From philosophical and logical perspectives
People inhabit a vast and intricate social network nowadays. In addition to our own decisions and actions, we confront those of various groups every day. Collective decisions and actions are more complex and bewildering compared to those made by individuals. As members of a collective, we contribute to its decisions, but our contributions may not always align with the outcome. We may also find ourselves excluded from certain groups and passively subjected to their influences without being aware of the source. We are used to being in overlapping groups and may switch identities, supporting or opposing the claims of particular groups. But rarely do we pause to think: What do we talk about when we talk about groups and their decisions?At the heart of this dissertation is the question of collective agency, i.e., in what sense can we treat a group as a rational agent capable of its action. There are two perspectives we take: a philosophical and logical one. The philosophical perspective mainly discusses the ontological and epistemological issues related to collective agency, sorts out the relevant philosophical history, and argues that the combination of a relational view of collective agency and a dispositional view of collective intentionality provides a rational and realistic account. The logical perspective is associated with formal theories of groups, it disregards the psychological content involved in the philosophical perspective, establishes a logical system that is sufficiently formal and objective, and axiomatizes the nature of a collective
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Policy options for food system transformation in Africa and the role of science, technology and innovation
As recognized by the Science, Technology and Innovation Strategy for Africa – 2024 (STISA-2024), science, technology and innovation (STI) offer many opportunities for addressing the main constraints to embracing transformation in Africa, while important lessons can be learned from successful interventions, including policy and institutional innovations, from those African countries that have already made significant progress towards food system transformation. This chapter identifies opportunities for African countries and the region to take proactive steps to harness the potential of the food and agriculture sector so as to ensure future food and nutrition security by applying STI solutions and by drawing on transformational policy and institutional innovations across the continent. Potential game-changing solutions and innovations for food system transformation serving people and ecology apply to (a) raising production efficiency and restoring and sustainably managing degraded resources; (b) finding innovation in the storage, processing and packaging of foods; (c) improving human nutrition and health; (d) addressing equity and vulnerability at the community and ecosystem levels; and (e) establishing preparedness and accountability systems. To be effective in these areas will require institutional coordination; clear, food safety and health-conscious regulatory environments; greater and timely access to information; and transparent monitoring and accountability systems
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