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Tesi sul tema "Complex systems"
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1
Magee, Christopher, e Weck Olivier de. "Complex System Classification". International Council On Systems Engineering (INCOSE), 2004. http://hdl.handle.net/1721.1/6753.
Testo completoAbstract (sommario):
The use of terms such as “Engineering Systems”, “System of systems” and others have been coming into greater use over the past decade to denote systems of importance but with implied higher complexity than for the term systems alone. This paper searches for a useful taxonomy or classification scheme for complex Systems. There are two aspects to this problem: 1) distinguishing between Engineering Systems (the term we use) and other Systems, and 2) differentiating among Engineering Systems. Engineering Systems are found to be differentiated from other complex systems by being human-designed and having both significant human complexity as well as significant technical complexity. As far as differentiating among various engineering systems, it is suggested that functional type is the most useful attribute for classification differentiation. Information, energy, value and mass acted upon by various processes are the foundation concepts underlying the technical types.Engineering Systems Division and Mechanical Engineering, Center for Innovation in Product Development
2
Venkatesh, Saligrama Ramaswamy. "System-identification for complex-systems". Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/10440.
Testo completo
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Chen, Angel Chia Ling. "Nesting complex systems". Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111700.
Testo completoAbstract (sommario):
Thesis: S.M. in Art, Culture and Technology, Massachusetts Institute of Technology, Department of Architecture, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (page 64).
This thesis discusses an artistic method of engaging with complex systems. The engagements take the form of inserting a certain something (an object, a task, a conversational prompt, myself) into a complex system with well-defined and elaborate technical processes serving specific and declared goals. The insertion is not meant to interrupt, disrupt, or destroy the system. The inserted thing is foreign to the system and is often understood as unproductive or absurd by it. However, the system can digest and process the thing successfully and spit it out the same way it does with what the system is meant to and does take in every day. This insertion is an act of nesting in the biological sense-making a nest from concocting foreign materials with existing materials-where the thing inserted becomes an anchor or an entry point from which a particular network of existing knowledge and relations are drawn out and revealed. Then, rigorous observations about what is revealed are made; materials produced by these encounters (between the things inserted and the systems) are collected. This gesture of insertion is an attempt at understanding a complex system without abstraction, reduction, or simplification. It is not possible to "see the whole picture" of these complex systems. However, one could, nonetheless, engage with it and allow a part (perhaps arbitrary to the system) to speak to the whole. The projects presented in this thesis engage with the complex systems of nanoscale fabrication, campus building construction, synthetic biology, and imaging technologies in the sciences. These seemingly disparate fields are united by an investigation of how emerging science and technology challenge an understanding of what a person is and how a person understands, as well as an interest in the very costly infrastructure that supports the new developments.
by Angel Chia Ling Chen.
S.M. in Art, Culture and Technology
4
Mwanga, Alifas Yeko. "Reliability modelling of complex systems". Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-12142006-121528.
Testo completo
5
Topaj, Dmitri. "Synchronization transitions in complex systems". Phd thesis, [S.l.] : [s.n.], 2001. http://pub.ub.uni-potsdam.de/2002/0006/topaj.pdf.
Testo completo
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Scudieri, Paul Anthony. "Information in Complex Product Systems". The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1236698805.
Testo completo
7
Reily, Todd R. (Todd Richard). "User experience design of complex systems". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/77063.
Testo completoAbstract (sommario):
Thesis (S.M. in Engineering and Management)--Massachusetts Institute of Technology, Engineering Systems Division, System Design and Management Program, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 104-105).
Over recent years, the global marketplace and its consumers have developed a mutual recognition for the rising prominence of design that delivers high quality user experience. For the provider of products and services, such design has emerged as a critical differentiator that creates new opportunities for revenue and drives customer loyalty. For the consumer, design can often surpass commoditized technical specifications as a basis for making purchase decisions. Nevertheless, despite their best intentions, many organizations still fail to successfully integrate design strategies into their existing processes and culture. This research examines the critical factors that enable successful implementation of design strategies under current market conditions in a way that produces sustained customer loyalty and revenue. Methods utilized in this research include one-on-one interviews, online surveys, and comparative case studies to ensure proper balance and perspective. The interviews were conducted with design leaders at organizations such as Philips and Frog Design. They covered the role that design plays at organizations, including the conditions necessary for successful design strategies and the barriers that they generally face. Surveys conducted for this research examined the personal experiences of 120 managers, engineers, and designers on the development of consumer-facing products, services, and systems. The result of these methods was a series of findings that supports the notion that a holistic "systems-based" approach offers competitive advantages to organizations looking to successfully implement a design-oriented strategy. It is this perspective that allows organizations to realize solutions that balance business objectives, technical capabilities, and design principles to meet customer intentions. It is proposed by this thesis that a systems-based approach has become necessary due to the ever-converging nature of today's networked products and services, particularly in the consumer marketplace. This thesis concludes with a framework of methods and principles for conceiving and designing user experiences for a complex market of convergent products and services. The framework borrows methods from Systems Thinking, Design Thinking, and User Experience Design to create a singular process that provides the clarity and simplicity necessary for a user experience amidst the complexity of a system design process.
by Todd R. Reily.
S.M.in Engineering and Management
8
Yap, Yee Jiun. "Topics in complex systems". Thesis, Brunel University, 2006. http://bura.brunel.ac.uk/handle/2438/5359.
Testo completoAbstract (sommario):
Fundamental laws of physics, although successful in explaining many phenomena observed in nature and society, cannot account for the behaviour of complex, non-Hamiltonian systems. Much effort has been devoted to better understanding the topological properties of these systems. Neither ordered nor disordered, these systems of high variability are found in many areas of science. Studies on sandpiles, earthquakes and lattice gases have all yielded evidence of complexity in the form of power law distributions. This scalefree characteristic is believed to be the hall-mark of complexity known as self-organised criticality. Systems in the self-organised critical state regulate themselves and are resistant to error and attacks. The aim of this thesis is to further current knowledge of complex systems by proposing and analysing three models of real systems. Statistical mechanics and numerical simulations are used to analyse these models. The first model mimics herd behaviour in social groups and encompasses growth and addition. It has been found that when the growth rate is fast enough, the group size distribution conforms to a power law. When the growth rate is slow, the system runs out of free agents in finite time. The second model aims to capture the basic empirical measurements from hospital waiting lists. This model illustrates how the power law distributions found in empirical studies might arise, but also indicates that these distributions are unlikely to be caused by the preferential behaviour of patients or physicians. The third model is a salary comparison model; the salary distributions of most of its variants are power laws. Both mean field and 1-d versions of the model are analysed, and differences between the two versions are identified by looking at the mean absolute difference between the salaries in each version.
9
Xie, Hang. "Waves in complex systems /". View abstract or full-text, 2008. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202008%20XIE.
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Ghosh, Soumyadip. "Complex self-sorting systems". College Park, Md. : University of Maryland, 2009. http://hdl.handle.net/1903/9248.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Chemistry and Biochemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Luo, Dapeng. "SYSTEM IDENTIFICATION AND FAULT DETECTION OF COMPLEX SYSTEMS". Doctoral diss., University of Central Florida, 2006. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/3583.
Testo completoAbstract (sommario):
The proposed research is devoted to devising system identification and fault detection approaches and algorithms for a system characterized by nonlinear dynamics. Mathematical models of dynamical systems and fault models are built based on observed data from systems. In particular, we will focus on statistical subspace instrumental variable methods which allow the consideration of an appealing mathematical model in many control applications consisting of a nonlinear feedback system with nonlinearities at both inputs and outputs. Different solutions within the proposed framework are presented to solve the system identification and fault detection problems. Specifically, Augmented Subspace Instrumental Variable Identification (ASIVID) approaches are proposed to identify the closed-loop nonlinear Hammerstein systems. Then fast approaches are presented to determine the system order. Hard-over failures are detected by order determination approaches when failures manifest themselves as rank deficiencies of the dynamical systems. Geometric interpretations of subspace tracking theorems are presented in this dissertation in order to propose a fault tolerance strategy. Possible fields of application considered in this research include manufacturing systems, autonomous vehicle systems, space systems and burgeoning bio-mechanical systems.Ph.D.
Department of Mechanical, Materials and Aerospace Engineering;
Engineering and Computer Science
Mechanical Engineering
12
Gupta, Amit. "Model reduction and simulation of complex dynamic systems /". Online version of thesis, 1990. http://hdl.handle.net/1850/11265.
Testo completo
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Liu, Zifan. "Complex systems and health systems, computational challenges". Thesis, Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS001V/document.
Testo completoAbstract (sommario):
Le calcul des valeurs propres intervient dans des modèles de maladies d’épidémiques et pourrait être utilisé comme un allié des campagnes de vac- cination dans les actions menées par les organisations de soins de santé. La modélisation épidémique peut être considérée, par analogie, comme celle des viruses d’ordinateur qui dépendent de l’état de graphe sous-jacent à un moment donné. Nous utilisons PageRank comme méthode pour étudier la propagation de l’épidémie et d’envisager son calcul dans le cadre de phé- nomène petit-monde. Une mise en œuvre parallèle de méthode multiple de "implicitly restar- ted Arnoldi method" (MIRAM) est proposé pour calculer le vecteur propre dominant de matrices stochastiques issus de très grands réseaux réels. La grande valeur de "damping factor" pour ce problème fait de nombreux algo- rithmes existants moins efficace, tandis que MIRAM pourrait être promet- teuse. Nous proposons également dans cette thèse un générateur de graphe parallèle qui peut être utilisé pour générer des réseaux synthétisés distri- bués qui présentent des structures "scale-free" et petit-monde. Ce générateur pourrait servir de donnée pour d’autres algorithmes de graphes également. MIRAM est mis en œuvre dans le cadre de trilinos, en ciblant les grandes données et matrices creuses représentant des réseaux sans échelle, aussi connu comme les réseaux de loi de puissance. Hypergraphe approche de partitionnement est utilisé pour minimiser le temps de communication. L’al- gorithme est testé sur un grille national de Grid5000. Les expériences sur les très grands réseaux tels que Twitter et Yahoo avec plus de 1 milliard de nœuds sont exécutées. Avec notre mise en œuvre parallèle, une accélération de 27× est satisfaite par rapport au solveur séquentielThe eigenvalue equation intervenes in models of infectious disease prop- agation and could be used as an ally of vaccination campaigns in the ac- tions carried out by health care organizations. The epidemiological model- ing techniques can be considered by analogy, as computer viral propagation which depends on the underlying graph status at a given time. We point out PageRank as method to study the epidemic spread and consider its calcula- tion in the context of small-world phenomenon. A parallel implementation of multiple implicitly restarted Arnoldi method (MIRAM) is proposed for calculating dominant eigenpair of stochastic matrices derived from very large real networks. Their high damp- ing factor makes many existing algorithms less efficient, while MIRAM could be promising. We also propose in this thesis a parallel graph gen- erator that can be used to generate distributed synthesized networks that display scale-free and small-world structures. This generator could serve as a testbed for graph related algorithms. MIRAM is implemented within the framework of Trilinos, targeting big data and sparse matrices representing scale-free networks, also known as power law networks. Hypergraph partitioning approach is employed to minimize the communication overhead. The algorithm is tested on a nation wide cluster of clusters Grid5000. Experiments on very large networks such as twitter and yahoo with over 1 billion nodes are conducted. With our parallel implementation, a speedup of 27× is met compared to the sequential solver
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Reis, Saulo-Davi Soares e. "Navegação em redes espacialmente correlacionadas". reponame:Repositório Institucional da UFC, 2009. http://www.repositorio.ufc.br/handle/riufc/12888.
Testo completoAbstract (sommario):
REIS, Saulo Davi Soares e. Navegação em redes espacialmente correlacionadas. 2009. 72 f. Dissertação (Mestrado em Física) - Programa de Pós-Graduação em Física, Departamento de Física, Centro de Ciências, Universidade Federal do Ceará, Fortaleza, 2009.Submitted by Edvander Pires (edvanderpires@gmail.com) on 2015-06-16T20:25:53Z No. of bitstreams: 1 2009_dis_sdsreis.pdf: 1915908 bytes, checksum: f38f094759742ce9d7cc35ad2d50209c (MD5)
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A significant number of real networks have well-defined spatial characteristics. We studied how network with spatially correlated topolgies can influence the processes of navigation through them. For this, we study the behavior of the average shortest-path length to networks defined within Kleinberg’s model [1, 2] to analyze the navigation dictated by rules of global knowledge. The Kleinberg’s model is characterized by allowing long-range connections between two vertices u and v distributed by a power-law probability distribution. For a better understanding of the topological characteristics presented by this family of networks, we applied the epidemic model susceptible-infected-susceptible (SIS) and we found that, we see that the Kleinberg’s model presents the small-world phenomenon only for a certain range of values of the clustering exponent α. We introduced a model of spatially embedded networks, conceptually based on the Kleinberg’s model. This model consist in introduction of a constrain to the distribution of long-range connections. We associate his constrain to a possible cost involved in the process of adding new long-range connections to the network. We studied how this cost constrain affects the navigation through the system, taking as a basis for comparison the work of Kleinberg for navigation with local knowledge, and our results conserning for navigation with global knowledge.
Um número significativo de redes reais apresentam características espaciais bem definidas. Nós estudamos como topologias de redes espacialmente correlacionadas podem influenciar processos de navegação através das mesmas. Para isso estudamos o comportamento do mínimo caminho médio para redes definidas dentro de modelo de Kleinberg para analisar a navegação ditada por regras de conhecimento global. O modelo que Kleinberg caracteriza-se por permitir conexões de longo alcance entre dois vértices u e v distribuídas por uma distribuição de probabilidade em lei de potência. Para um melhor entendimento das características topológicas apresentadas por essa família de redes, nós aplicamos o modelo epidêmico suscetível-infectado-suscetível (SIS), e com isso verificamos que o modelo de Kleinberg apresenta fenômeno de mundo pequeno apenas para uma determinada faixa de valores assumidos pelo expoente de agregação α. Em seguida, introduzimos um modelo de redes espacialmente embutidas, conceitualmente inspirado no modelo de Kleinberg. Este traduz-se na introdução de um vínculo para a distribuição das conexões de longo alcance. Associamos este vínculo a um possível custo envolvido no processo de adição de novas conexões de longo alcance à rede. Estudamos como esse vínculo no custo afeta a navegação na rede, tendo como base de comparação os trabalhos de Kleinberg para a navegação com conhecimento local da topologia, e nossos resultados considerando a navegação com conhecimento global.
15
Siddique, Shahnewaz. "Failure mechanisms of complex systems". Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/51831.
Testo completoAbstract (sommario):
Understanding the behavior of complex, large-scale, interconnected systems in a rigorous and structured manner is one of the most pressing scientific and technological challenges of current times. These systems include, among many others, transportation and communications systems, smart grids and power grids, financial markets etc. Failures of these systems have potentially enormous social, environmental and financial costs. In this work, we investigate the failure mechanisms of load-sharing complex systems. The systems are composed of multiple nodes or components whose failures are determined based on the interaction of their respective strengths and loads (or capacity and demand respectively) as well as the ability of a component to share its load with its neighbors when needed. Each component possesses a specific strength (capacity) and can be in one of three states: failed, damaged or functioning normally. The states are determined based on the load (demand) on the component.
We focus on two distinct mechanisms to model the interaction between components strengths and loads. The first, a Loss of Strength (LOS) model and the second, a Customer Service (CS) model. We implement both models on lattice and scale-free graph network topologies. The failure mechanisms of these two models demonstrate temporal scaling phenomena, phase transitions and multiple distinct failure modes excited by extremal dynamics. We find that the resiliency of these models is sensitive to the underlying network topology. For critical ranges of parameters the models demonstrate power law and exponential failure patterns. We find that the failure mechanisms of these models have parallels to failure mechanisms of critical infrastructure systems such as congestion in transportation networks, cascading failure in electrical power grids, creep-rupture in composite structures, and draw-downs in financial markets. Based on the different variants of failure, strategies for mitigating and postponing failure in these critical infrastructure systems can be formulated.
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Kleineberg, Kaj Kolja. "Evolution and ecology of the digital world: A complex systems perspective". Doctoral thesis, Universitat de Barcelona, 2016. http://hdl.handle.net/10803/400404.
Testo completoAbstract (sommario):
Online social networks (OSNs) enable researchers to study the social universe at a previously unattainable scale. The worldwide impact and the necessity to sustain their rapid growth emphasize the importance to unravel the laws governing their evolution. We present a quantitative two-parameter model which reproduces the entire topological evolution of a quasi-isolated OSN with unprecedented precision from the birth of the network. This allows us to precisely gauge the fundamental macroscopic and microscopic mechanisms involved. Our findings suggest that the coupling between the real pre-existing underlying social structure, a viral spreading mechanism, and mass media influence govern the evolution of OSNs. The empirical validation of our model, on a macroscopic scale, reveals that virality is four to five times stronger than mass media influence and, on a microscopic scale, individuals have a higher subscription probability if invited by weaker social contacts, in agreement with the "strength of weak ties" paradigm. The simultaneous existence of numerous digital services naturally raises the question under which conditions these services can coexist. In analogy to population dynamics, the digital world is forming a complex ecosystem of interacting networks whose fitnesses depend on their ability to attract and maintain users' attention, which constitutes a limited resource. We introduce an ecological theory of the digital world which exhibits a stable coexistence of several networks as well as the domination of a single one, in contrast to the principle of competitive exclusion. Interestingly, our model also predicts that the most probable outcome is the coexistence of a moderate number of services, in agreement with empirical observations. In addition, we discuss the impact of heterogeneity in network fitnesses induced by competition between an international network, such as Facebook, and local services. To this end, we construct a 1:1000 scale model of the digital world, consisting of the 80 countries with the most Internet users. We show how inter-country social ties induce increased fitness of the international network. Under certain conditions, this leads to the extinction of local networks; whereas under different conditions, local networks can persist and even dominate the international network completely. Finally, we investigate how multiple coexisting networks, which form a so called multiplex system, facilitate search and navigation with only local knowledge. This task is especially important in decentralized architectures. In particular, we show that multiplex systems are not random combinations of single network layers. Instead, they are organized in specific ways dictated by hidden geometric correlations between the individual layers. We find that these correlations are strong in different real multiplexes, and form a key framework for answering many important questions. Specifically, we show that these geometric correlations facilitate: (i) the definition and detection of multidimensional communities, which are sets of nodes that are simultaneously similar in multiple layers; (ii) accurate trans-layer link prediction, where connections in one layer can be predicted by observing the hidden geometric space of another layer; and (iii) efficient targeted navigation in the multilayer system using only local knowledge, which outperforms navigation in the single layers only if the geometric correlations are sufficiently strong. Interestingly, many real systems fulfill these conditions. To conclude, from a system-level perspective, a prospering future in the digital age comprised of a diverse digital landscape with interacting, decentralized architectures is possible, but so is the opposite. It remains a task for society to create sufficient awareness and the correct incentives to create this future we desire.Esta tesis está dedicada a los retos de un mundo interconectado que ha emergido a partir de la reciente revolución digital en el que servicios digitales se desarrollan y compiten en la ausencia de control central. Por tanto, herramientas, ideas y técnicas de análisis de sistemas complejos son útiles y especialmente adecuadas para describir la evolución y competencia entre redes sociales online. El éxito del Internet ha conectado individuos a escalas sin precedentes y la Web 2.0 promociona hoy en día colaboración global y el intercambio de ideas casi instantáneo. Sin embargo, la dominación de unos pocos poderosos monopolios de información representa un peligro para la libertad de ideas y decisiones de individuos. Por tanto, dos factores son esenciales para un futuro próspero en la era digital: diversidad digital y decentralización. En cuanto al primero, hemos introducido modelos basados en observaciones empíricas que permiten entender mejor la dinámica y las interacciones competitivas de las redes sociales online, los sistemas claves en el cosmos de la Web 2.0. En particular, nuestros descubrimientos revelan las condiciones en las cuales la diversidad digital se puede sostener. Con respecto al segundo, el diseño de arquitecturas descentralizadas contiene retos específicos, entre los que nos dirigimos especialmente a la búsqueda y navegación basada exclusivamente en conocimiento local. Hemos revelado en qué condiciones la existencia de muchas redes interaccionando facilita estas tareas. Afortunadamente, muchos sistemas reales cumplen estas condiciones. Para concluir, desde una perspectiva a nivel de sistema, un futuro próspero en el mundo digital compuesto por un paisaje digital diverso con arquitecturas descentralizadas en constante interacción es posible, pero no seguro. En esta situación, la conciencia, así como la creación de los incentivos adecuados, son retos importantes que nuestra sociedad debe afrontar. Crear conciencia suficiente e incentivos correctos para crear ese futuro sigue siendo un reto para la sociedad.
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Devereaux, Jaime E. (Jaime Erin). "Obsolescence : a systems engineering and management approach for complex systems". Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/59233.
Testo completoAbstract (sommario):
Thesis (S.M. in System Design and Management)--Massachusetts Institute of Technology, Engineering Systems Division, Technology and Policy Program, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 79-81).
Obsolescence mitigation is an increasingly important aspect of large systems development & maintenance that has often only been considered once obsolescence is imminent. For long lifecycle systems, this has become a major concern as the lifecycles of the components that are encompassed within these systems are often far shorter - up to ten times shorter - than the overall system lifecycle. Many defense systems can be characterized in this manner and therefore require obsolescence mitigation approaches to ensure the continuing ability for the system to perform and evolve. Current system-level obsolescence mitigation practices make recommendations for designing new systems to slow the onset of obsolescence and make the system more flexible when change for obsolescence is required. However, currently fielded systems were often not designed with this in mind. Other obsolescence mitigation techniques focus only on the approach to mitigating component-level obsolescence locally without examining the impact of the change on the system as a whole. This thesis combines the recommended approaches for obsolescence mitigation, the experience and lessons learned for obsolescence mitigation on a real-world case study system gained from interviews with key subject matter experts, along with systems engineering techniques for dealing with engineering change in systems to develop a robust systems engineering and management approach for obsolescence in large complex systems. The thesis provides the reader with a flow chart and a clustered DSM of the tasks along with a checklist that could be used with this obsolescence engineering and management approach.
by Jaime E. Devereaux.
S.M.in System Design and Management
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Braungardt, Sibylle. "Complex systems for quantum technologies". Doctoral thesis, Universitat Politècnica de Catalunya, 2011. http://hdl.handle.net/10803/35871.
Testo completo
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Zhao, Zhenyuan. "Dynamical Grouping in Complex Systems". Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/498.
Testo completoAbstract (sommario):
Quantifying the behavior of complex systems arguably presents the common ¡°hard¡±problem across the physical, biological, social, economic sciences. Individual-based or agent-based models have proved useful in a variety of different real world systems: from the physical, biological, medical domains through to social and even financial domains. There are many different models in each of these fields, each with their own particular assumptions, strengths and weaknesses for particular application areas. However, there is a lack of minimal model analysis in which both numerical and analytic results can be obtained, and hence allowing different application domains to be analyzed on a common footing. This thesis focuses on a few simple, yet highly non-trivial, minimal models of a population of interacting objects (so-called agents) featuring internal dynamical grouping. In addition to analyzing these models, I apply them to a number of distinct real world systems. Both the numerical and analytical results suggest that these simple models could be key factors in explaining the overall collective behavior and emergent properties in a wide range of real world complex systems. In particular, I study variants of a particular model (called the EZ model) in order to explain the attrition time in modern conflicts, and the evolution of contagion phenomena in such a dynamically evolving population. I also study and explain the empirical data obtained for online guilds and offline gangs, leading to a team-based model which captures the common quantitative features of the data. I then move on to develop a resource competition model (i.e. the so-called El Farol model) and apply it to the carbon emissions market, mapping the different market factors into model parameters which enable me to explore the potential market behaviors under a variety of scenarios.
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Fischer, Andreas. "Modelling Complex Systems: Tree Structures". Doctoral thesis, Universitätsbibliothek Chemnitz, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200800123.
Testo completoAbstract (sommario):
Der Zustandsraum ist ein sehr wichtiges und grundlegendes Konzept für die Untersuchung komplexer Systeme. Alle Eigenschaften des Systems können anhand der Struktur dieses Raumes verstanden werden. Aufgrund der immensen Größe des Zustandsraumes eines realen komplexen Systems ist eine vergröberte Beschreibung unumgänglich für dessen Analyse. In dieser Arbeit werden, aufbauend auf dem lang etablierten Modell der hierarchischen Bäume, spezielle Aspekte komplexer Systeme untersucht. Gleichzeitig wird das verwendete Modell in geeigneter Weise erweitert und verbessert. Im ersten Teil der Forschungsarbeit werden die Besonderheiten des Wahrscheinlichkeitsflusses an einem einzelnen Sattelpunkt einer Energielandschaft detailliert betrachtet. Die Einflüsse verschiedener Parameter wie Energietiefe, Zustandsdichte und Konnektivität werden unabhängig voneinander und im Zusammenspiel untersucht. Im zweiten Teil wird ein vollständiges System, das komplexes Verhalten zeigt, untersucht, wobei besonderes Gewicht auf seine Wechselwirkung, d.h. seinen Energieaustausch mit der Umgebung, gelegt wird. Es kann gezeigt werden, daß das hierarchische Relaxationsverhalten, welches bei anderen Varianten komplexer Systeme beobachtet werden konnte, im Baummodell bereits enthalten ist. Neben den bisher untersuchten, auf Energielandschaften basierenden Systemen besitzen auch turbulente Diffusionsprozesse hierarchische Strukturen. Im dritten Teil der Arbeit wird die Baumstruktur verwendet, um turbulente Superdiffusionsprozesse zu modellieren. Das dabei beobachtete Diffusionsverhalten wird mit vier bekannten mathematischen Modellen verglichen. Die Ergebnisse zeigen, daß nur eines der untersuchten Modelle den vom Baummodell beschriebenen turbulenten Transport in akzeptabler Weise nachbildetThe state space is a very important and fundamental concept for the treatment of complex systems. All the system's properties can be understood by means of its structure. Due to the gigantic extent of a real system's state space, a coarse grained approach is inevitable for the analysis. In this work, based on the well established model of hierarchical trees, particular aspects of complex systems have been studied, while at the same time several extensions to the model have been made. In the first part of this research work the features of the probability flow are treated in detail at a single saddle point in the energy landscape. Influences of various parameters like energetic depth, density of states and connectivity are studied isolated and in their interaction. In the second part a whole system showing complex behavior is being considered, especially its energy exchange with the surroundings. It can be demonstrated that the hierarchical relaxation behavior observed in other realizations of complex systems is intrinsically covered by the tree model. Beside energy landscape based systems turbulent diffusion processes possess hierarchical structures, too. In the third part the tree structure has been used to model a turbulent superdiffusion process. The diffusion behavior observed there has been compared with four well known diffusion equation approaches. The results show that only one of the discussed continuum diffusion equations can model the turbulent transport based on the tree model in acceptable fashion
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Lenz, Malte, e Johan Rhodin. "Reliability calculations for complex systems". Thesis, Linköpings universitet, Reglerteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-69952.
Testo completoAbstract (sommario):
Functionality for efficient computation of properties of system lifetimes was developed, based on the Mathematica framework. The model of these systems consists of a system structure and the components independent lifetime distributions. The components are assumed to be non-repairable. In this work a very general implementation was created, allowing a large number of lifetime distributions from Mathematica for all the component distributions. All system structures with a monotone increasing structure function can be used. Special effort has been made to compute fast results when using the exponential distribution for component distributions. Standby systems have also been modeled in similar generality. Both warm and cold standby components are supported. During development, a large collection of examples were also used to test functionality and efficiency. A number of these examples are presented. The implementation was evaluated on large real world system examples, and was found to be efficient. New results are presented for standby systems, especially for the case of mixed warm and cold standby components.
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Becks, Lutz. "Complex dynamics in microbial systems /". Berlin : Logos Berlin, 2007. http://deposit.d-nb.de/cgi-bin/dokserv?id=2941202&prov=M&dok_var=1&dok_ext=htm.
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Suphanit, B. "Design of complex distillation systems". Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.504693.
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Fain, Mikhail. "Control of complex biomechanical systems". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/45401.
Testo completoAbstract (sommario):
Humans show stunning performance on a variety of manipulation tasks. However, little is known about the computation that the human brain performs to accomplish these tasks. Recently, anatomically correct tendon-driven models of the human hand have been developed, but controlling them remains an issue. In this thesis, we present a computationally efficient feedback controller, capable of dealing with the complexity of these models. We demonstrate its abilities by successfully performing tracking and reaching tasks for an elaborated model of the human index finger.
The controller, called One-Step-Ahead controller, is designed in a hierarchical fashion, with the high-level controller determining the desired trajectory and the low-level controller transforming it into muscle activations by solving a constrained linear least squares problem. It was proposed to use equilibrium controls as a feedforward command, and learn the controller's parameters online by stabilizing the plant at various configurations. The conducted experiments suggest the feasibility of the proposed learning approach for the index finger model.
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Lim, Brian Yoo-Jin. "Principles for architecting complex systems". Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/9902.
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Slagle, Jason C. "Architecting complex systems for robustness". Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/43109.
Testo completoAbstract (sommario):
Thesis (S.M.)--Massachusetts Institute of Technology, System Design and Management Program, 2007.Vita.
Includes bibliographical references (p. 121-128).
Robust design methodologies are frequently utilized by organizations to develop robust and reliable complex systems. The intent of robust design is to create systems that are insensitive to variations from production, the environment, and time and use. While this process is effective, it can also be very time consuming and resource intensive for an engineering team. In addition, most robust design activity takes place at the detailed design phase, when the majority of the product life cycle cost has already been committed. Addressing robustness and the "ilities" at the architecture level may be more effective because it is the earliest and highest leverage point in the product development process. Furthermore, some system architectures are inherently more robust than others. In this thesis, a framework based on principles is proposed to architect complex systems for type I and II robustness. The principles are obtained by tracing the architectural evolution of the jet engine, which is an extremely complex system that has evolved to high reliability. This framework complements existing robust design methods, while simultaneously incorporating the robustness focus earlier in the product development process.
by Jason C. Slagle.
S.M.
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Fejer, Szilard. "Self-assembly in complex systems". Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611771.
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Afzal, Nasrin. "Aging processes in complex systems". Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/23901.
Testo completoAbstract (sommario):
Recent years have seen remarkable progress in our understanding of physical aging in nondisordered systems with slow, i.e. glassy-like dynamics. In many systems a single dynamical length L(t), that grows as a power-law of time t or, in much more complicated cases, as a logarithmic function of t, governs the dynamics out of equilibrium. In the aging or dynamical scaling regime, these systems are best characterized by two-times quantities, like dynamical correlation and response functions, that transform in a specific way under a dynamical scale transformation. The resulting dynamical scaling functions and the associated non-equilibrium exponents are often found to be universal and to depend only on some global features of the system under investigation.
We discuss three different types of systems with simple and complex aging properties, namely reaction diffusion systems with a power growth law, driven diffusive systems with a logarithmic growth law, and a non-equilibrium polymer network that is supposed to capture important properties of the cytoskeleton of living cells.
For the reaction diffusion systems, our study focuses on systems with reversible reaction diffusion and we study two-times functions in systems with power law growth. For the driven diffusive systems, we focus on the ABC model and a related domain model and measure two- times quantities in systems undergoing logarithmic growth. For the polymer network model, we explain in some detail its relationship with the cytoskeleton, an organelle that is responsible for the shape and locomotion of cells. Our study of this system sheds new light on the non- equilibrium relaxation properties of the cytoskeleton by investigating through a power law growth of a coarse grained length in our system.Ph. D.
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Steyn, Jacques. "Language : a complex-systems approach". Doctoral thesis, University of Cape Town, 1994. http://hdl.handle.net/11427/19415.
Testo completoAbstract (sommario):
Mainstream twentieth-century linguistics, a segregational approach, cannot explain the most obvious characteristics of language. The reasons for this are investigated. It is concluded that linguistics suffers from an incoherent conceptual framework which is the result of influences from three major sources: 1. The desire to establish linguistics as a proper science which led to the acceptance of a mechanistic and positivistic view of science and a pre-quantum conception of matter. 2. The language myth: there are many notions about language and related issues which we have inherited from our ancestors and tacitly accepted without scrutiny. Contemporary ideas about language are biased by this inherited stock of 'knowledge'. 3. Saussure's theory of language, later adopted and adapted by Chomsky, in which the 'true object of linguistic investigation' is abstracted away from what we ordinarily view as language. Together these three sources resulted in a peculiar view of language which cannot explain the most obvious things about it. The proposed alternative view, an integrational approach, redefines language in the holistic terms of a complex-systems approach. Language is the outcome of the dynamic interaction between social and physiological systems -- particular attention is paid to consciousness. Neither language, society or culture is an 'object', but is created through the interaction between individuals in communicative situations. Language is not 'being', but results from 'becoming'. Meaning is not given in advance, but created in each event of communication. Meaning is not a static closed system, but an open system which is dynamically constructed from moment to moment. Concepts of mathematical topology (fractal geometry and catastrophe theory), non-linear, dynamic, open and complex systems, and of chaology are used as conceptual tools to break away from the stronghold our inherited view of language has on our contemporary thinking about it.
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Topcu, Taylan Gunes. "Management of Complex Sociotechnical Systems". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/97844.
Testo completoAbstract (sommario):
Sociotechnical systems (STSs) rely on the collaboration between humans and autonomous decision-making units to fulfill their objectives. Highly intertwined social and technical contextual factors influence the collaboration between these human and engineered elements, and consequently the performance characteristics of the STS. In the next two decades, the role allocated to STSs in our society will drastically increase. Thus, the effective design of STSs requires an improved understanding of the human-autonomy interdependency.
This dissertation brings together management science along with systems thinking and uses a mixed-methods approach to investigate the interdependencies between people and the autonomous systems they collaborate within complex socio-technical enterprises. The dissertation is organized in three mutually exclusive essays, each investigating a distinct facet of STSs: safe management, collaboration, and efficiency measurement.
The first essay investigates the amount of work allocated to safety-critical decision makers and quantifies Rasmussen's workload boundary that represents the limit of attainable workload. The major contribution of this study is to quantify the qualitative theoretical construct of the workload boundary through a Pareto-Koopmans frontier. This frontier allows one to capture the aggregate impact of the social and technical factors that originate from operational conditions on workload.
The second essay studies how teams of humans and their autonomous partners share work, given their subjective preferences and contextual operational conditions. This study presents a novel integration of machine learning algorithms in an efficiency measurement framework to understand the influence of contextual factors. The results demonstrate that autonomous units successfully handle relatively simple operational conditions, while complex operational conditions require both workers and their autonomous counterparts to collaborate towards common objectives.
The third essay explores the complementary and contrasting roles of efficiency measurement approaches that deal with the influence of contextual factors and their sensitivity to sample size. The results are organized in a structured taxonomy of their fundamental assumptions, limitations, mathematical structure, sensitivity to sample size, and their practical usefulness.
To summarize, this dissertation provides an interdisciplinary and pragmatic research approach that benefits from the strengths of both theoretical and data-driven empirical approaches. Broader impacts of this dissertation are disseminated among the literatures of systems engineering, operations research, management science, and mechanical design.Doctor of Philosophy
A system is an integrated set of elements that achieve a purpose or goal. An autonomous system (ADS) is an engineered element that often substitutes for a human decision-maker, such as in the case of an autonomous vehicle. Sociotechnical systems (STSs) are systems that involve the collaboration of a human decision-maker with an ADS to fulfill their objectives. Historically, STSs have been used primarily for handling safety critical tasks, such as management of nuclear power plants. By design, STSs rely heavily on a collaboration between humans and ADS decision-makers. Therefore, the overall characteristics of a STS, such as system safety, performance, or reliability; is fully dependent on human decisions. The problem with that is that people are independent entities, who can be influenced by operational conditions. Unlike their engineered counterparts, people can be cognitively challenged, tired, or distracted, and consequently make mistakes. The current dependency on human decisions, incentivize business owners and engineers alike to increase the level of automation in engineered systems. This allows them to reduce operational costs, increase performance, and minimize human errors. However, the recent commercial aircraft accidents (e.g., Boeing 737-MAX) have indicated that increasing the level of automation is not always the best strategy. Given that increasing technological capabilities will spread the adoption of STSs, vast majority of existing jobs will either be fully replaced by an ADS or will change from a manual set-up into a STS. Therefore, we need a better understanding of the relationships between social (human) and engineered elements. This dissertation, brings together management science with systems thinking to investigate the dependencies between people and the autonomous systems they collaborate within complex socio-technical enterprises. The dissertation is organized in three mutually exclusive essays, each investigating a distinct facet of STSs: safe management, collaboration, and efficiency measurement. The first essay investigates the amount of work handled by safety-critical decision makers in STSs. Primary contribution of this study is to use an analytic method to quantify the amount of work a person could safely handle within a STSs. This method also allows to capture the aggregate impact of the social and technical factors that originate from operational conditions on workload. The second essay studies how teams of humans and their autonomous partners share work, given their preferences and operational conditions. This study presents a novel integration of machine learning algorithms to understand operational influences that propel a human-decision maker to handle the work manually or delegate it to ADSs. The results demonstrate that autonomous units successfully handle simple operational conditions. More complex conditions require both workers and their autonomous counterparts to collaborate towards common objectives. The third essay explores the complementary and contrasting roles of data-driven analytical management approaches that deal with the operational factors and investigates their sensitivity to sample size. The results are organized based on their fundamental assumptions, limitations, mathematical structure, sensitivity to sample size, and their practical usefulness. To summarize, this dissertation provides an interdisciplinary and pragmatic research approach that benefits from the strengths of both theoretical and data-driven empirical approaches. Broader impacts of this dissertation are disseminated among the literatures of systems engineering, operations research, management science, and mechanical design.
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Grimm, Alexander Rudolf. "Taming of Complex Dynamical Systems". Thesis, Virginia Tech, 2013. http://hdl.handle.net/10919/24775.
Testo completoAbstract (sommario):
The problem of establishing local existence and uniqueness of solutions to systems of differential equations is well understood and has a long history. However, the problem of proving global existence and uniqueness is more difficult and fails even for some very simple ordinary differential equations. It is still not known if the 3D Navier-Stokes equation have global unique solutions and this open problem is one of the Millennium Prize Problems. However, many of these mathematical models are extremely useful in the understanding of complex physical systems. For years people have considered methods for modifying these equations in order to obtain models that still capture the observed fundamental physics, but for which one can rigorously establish global results. In this thesis we focus on a taming method to achieve this goal and apply taming to modeling and numerical problems. The method is also applied to a class of nonlinear differential equations with conservative nonlinearities and to Burgers’ Equation with Neumann boundary conditions. Numerical results are presented to illustrate the ideas.Master of Science
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Gardenghi, Melissa K. "Multiobjective optimization for complex systems". Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1252937757/.
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Shone, N. "Detecting misbehaviour in a complex system-of-systems environment". Thesis, Liverpool John Moores University, 2014. http://researchonline.ljmu.ac.uk/4537/.
Testo completoAbstract (sommario):
Modern systems are becoming increasingly complex, integrated and distributed, in order to meet the escalating demands for functionality. This has given rise to concepts such as system-of-systems (SoS), which organise a myriad of independent component systems into a collaborative super-system, capable of achieving unmatchable levels of functionality. Despite its advantages, SoS is still an infantile concept with many outstanding security concerns, including the lack of effective behavioural monitoring. This can be largely attributed to its distributed, decentralised and heterogeneous nature, which poses many significant challenges. The uncertainty and dynamics of both the SoS’s structure and function poses further challenges to overcome. Due to the unconventional nature of a SoS, existing behavioural monitoring solutions are often inadequate as they are unable to overcome these challenges. This monitoring deficiency can result in the occurrence of misbehaviour, which is one of the most serious yet underestimated security threats facing SoSs and their components. This thesis presents a novel misbehaviour detection framework specifically developed for operation in a SoS environment. By combining the use of uniquely calculated behavioural threshold profiles and periodic threshold adaptation, the framework is able to cope with monitoring the dynamic behaviour and suddenly occurring changes that affect threshold reliability. The framework improves SoS contribution and monitoring efficiency by controlling monitoring observations using statecharts, which react to the level of behavioural threat perceived by the system. The accuracy of behavioural analysis is improved by using a novel algorithm to quantify detected behavioural abnormalities, in terms of their level of irregularity. The framework utilises collaborative behavioural monitoring to increase the accuracy of the behavioural analysis, and to combat the threat posed by training based attacks to the threshold adaptation process. The validity of the collaborative behavioural monitoring is assured by using the novel behavioural similarity assessment algorithm, which selects the most behaviourally appropriate SoS components to collaborate with. The proposed framework and its subsequent techniques are evaluated via numerous experiments. These examine both the limitations and relative merits when compared to monitoring solutions and techniques from similar research areas. The results of these conclude that the framework is able to offer misbehaviour monitoring in a SoS environment, with increased efficiency and reduced false positive rates, false negative rates, resource usage and run-time requirements.
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Aragon, Lasumar (Mark) R. "Technology insertion considerations for complex system of systems development". Thesis, Monterey, Calif. : Naval Postgraduate School, 2008. http://edocs.nps.edu/npspubs/scholarly/theses/2008/Sept/08Sep%5FAragon.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Systems Engineering)--Naval Postgraduate School, September 2008.Thesis Advisor(s): Paulo, Eugene. "September 2008." Description based on title screen as viewed on October 31, 2008. Includes bibliographical references (p. 63-64). Also available in print.
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Yildirim, Unal. "Function Modelling of Complex Multidisciplinary Systems. Development of a System State Flow Diagram Methodology for Function Decomposition of Complex Multidisciplinary Systems". Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14385.
Testo completoAbstract (sommario):
The complexity of technical systems has increased significantly in order to address evolving customer needs and environmental concerns. From a product development process viewpoint, the pervasive nature of multi-disciplinary systems (i.e. mechanical, electrical, electronic, control, software) has brought some important integration challenges to overcome conventional disciplinary boundaries imposed by discipline specific approaches. This research focuses on functional reasoning, aiming to develop a structured framework based on the System State Flow Diagram (SSFD) for function modelling of complex multidisciplinary systems on a practical and straightforward basis. The framework is developed at two stages. 1) The development of a prototype for the SSFD framework. The proposed SSFD framework are tested and validated through application to selected desktop case studies. 2) Further development and extension of the SSFD framework for the analysis of complex multidisciplinary systems with multiple operation modes and functional requirements. The developed framework is validated on real world case studies collaborated with industrial partners. The main conclusion of this research is that the SSFD framework offers a rigorous and coherent function modelling methodology for the analysis of complex multidisciplinary systems. Further advantages of the SSFD framework is that 1) the effectiveness of the Failure Mode Avoidance (FMA) process can be enhanced by integrating the SSFD framework with relevant tools of the FMA process, and 2) the integration of the SSFD with the SysML systems engineering diagrams is doable, which can promote the take-up of the approach in industry.
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Case, Denise Marie. "Engineering complex systems with multigroup agents". Diss., Kansas State University, 2015. http://hdl.handle.net/2097/19045.
Testo completoAbstract (sommario):
Doctor of PhilosophyComputing and Information Sciences
Scott A. DeLoach
As sensor prices drop and computing devices continue to become more compact and powerful, computing capabilities are being embedded throughout our physical environment. Connecting these devices in cyber-physical systems (CPS) enables applications with significant societal impact and economic benefit. However, engineering CPS poses modeling, architecture, and engineering challenges and, to fully realize the desired benefits, many outstanding challenges must be addressed. For the cyber parts of CPS, two decades of work in the design of autonomous agents and multiagent systems (MAS) offers design principles for distributed intelligent systems and formalizations for agent-oriented software engineering (AOSE). MAS foundations offer a natural fit for enabling distributed interacting devices. In some cases, complex control structures such as holarchies can be advantageous. These can motivate complex organizational strategies when implementing such systems with a MAS, and some designs may require agents to act in multiple groups simultaneously. Such agents must be able to manage their multiple associations and assignments in a consistent and unambiguous way. This thesis shows how designing agents as systems of intelligent subagents offers a reusable and practical approach to designing complex systems. It presents a set of flexible, reusable components developed for OBAA++, an organization-based architecture for single-group MAS, and shows how these components were used to develop the Adaptive Architecture for Systems of Intelligent Systems (AASIS) to enable multigroup agents suitable for complex, multigroup MAS. This work illustrates the reusability and flexibility of the approach by using AASIS to simulate a CPS for an intelligent power distribution system (IPDS) operating two multigroup MAS concurrently: one providing continuous voltage control and a second conducting discrete power auctions near sources of distributed generation.
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Henneman, Richard Lewis. "Human problem solving in complex hierarchical large scale systems". Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/25432.
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Kingston, Kenneth Samuel. "Applications of complex adaptive systems approaches to coastal systems". Thesis, University of Plymouth, 2003. http://hdl.handle.net/10026.1/474.
Testo completoAbstract (sommario):
This thesis investigates the application of complex adaptive systems approaches (e.g. Artificial Neural Networks and Evolutionary Computation) to the study of coastal hydrodynamic and morphodynamic behaviour. Traditionally, nearshore morphological coastal system studies have developed an understanding of those physical processes occurring on both short temporal, and small spatial scales with a large degree of success. The associated approaches and concepts used to study the coastal system at these scales have primarily been linear in nature. However, when these approaches to studying the coastal system are extended to investigating larger temporal and spatial scales, which are commensurate with the aims of coastal management, results have had less success. The lack of success in developing an understanding of large scale coastal behaviour is to a large extent attributable to the complex behaviour associated with the coastal system. This complexity arises as a result of both the stochastic and chaotic nature of the coastal system. This allows small scale system understanding to be acquired but prevents the larger scale behaviour to be predicted effectively. This thesis presents four hydro-morphodynamic case studies to demonstrate the utility of complex adaptive system approaches for studying coastal systems. The first two demonstrate the application of Artificial Neural Networks, whilst the latter two illustrate the application of Evolutionary Computation. Case Study #1 considers the nature of the discrepancy between the observed location of wave breaking patterns over submerged sandbars and the actual sandbar locations. Artificial Neural Networks were able to quantitatively correct the observed locations to produce reliable estimates of the actual sand bar locations. Case Study #2 considers the development of an approach for the discrimination of shoreline location in video images for the production of intertidal maps of the nearshore region. In this case the system modelled by the Artificial Neural Network is the nature of the discrimination model carried out by the eye in delineating a shoreline feature between regions of sand and water. The Artificial Neural Network approach was shown to robustly recognise a range of shoreline features at a variety of beaches and hydrodynamic settings. Case Study #3 was the only purely hydrodynamic study considered in the thesis. It investigated the use of Evolutionary Computation to provide means of developing a parametric description of directional wave spectra in both reflective and nonreflective conditions. It is shown to provide a unifying approach which produces results which surpassed those achieved by traditional analysis approaches even though this may not strictly have been considered as a fiddly complex system. Case Study #4 is the most ambitious application and addresses the need for data reduction as a precursor when trying to study large scale morphodynamic data sets. It utilises Evolutionary Computation approaches to extract the significant morphodynamic variability evidenced in both directly and remotely sampled nearshore morphologies. Significant data reduction is achieved whilst reWning up to 90% of the original variability in the data sets. These case studies clearly demonstrate the ability of complex adaptive systems to be successfully applied to coastal system studies. This success has been shown to equal and sometimess surpass the results that may be obtained by traditional approaches. The strong performance of Complex Adaptive System approaches is closely linked to the level of complexity or non-linearity of the system being studied. Based on a qualitative evaluation, Evolutionary Computation was shown to demonstrate an advantage over Artificial Neural Networks in terms of the level of new insights which may be obtained. However, utility also needs to consider general ease of applicability and ease of implementation of the study approach. In this sense, Artificial Neural Networks demonstrate more utility for the study of coastal systems. The qualitative assessment approach used to evaluate the case studies in this thesis, may be used as a guide for choosing the appropriateness of either Artificial Neural Networks or Evolutionary Computation for future coastal system studies.
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Antiqueira, Lucas. "Relações da estrutura de redes complexas com as dinâmicas do passeio aleatório, de transporte e de sincronização". Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-13032012-100543/.
Testo completoAbstract (sommario):
O relacionamento entre estrutura e dinâmica em redes complexas foi considerado utilizando-se uma ampla gama de diferentes técnicas. Diversas redes reais foram estudadas em termos das correlações entre grau e atividade. A medida de atividade é definida como a proporção de visitas por vértice no regime estacionário do passeio aleatório simples. O estudo desse tipo de correlação é importante pois pode fornecer subsídios para que uma propriedade dinâmica de um vértice possa ser obtida somente analisando-se seu(s) grau(s). O conceito de acessibilidade foi abordado nesse contexto, permitindo que fossem evidenciadas diferentes correlações, em redes como a WWW, de acordo com a intensidade de acessibilidade dos vértices. Propôs-se também um novo modelo de rede baseado no crescimento do número de vértices em que novas conexões são criadas com probabilidade proporcional à atividade de cada vértice. Esse modelo pode ser entendido como uma generalização do modelo de Barabási e Albert para redes com arestas direcionadas. Utilizando-se um conjunto de diversas medidas estruturais, mostrou-se que o novo modelo apresenta, entre outros modelos tradicionais de redes, a maior compatibilidade com três redes corticais. Foi também desenvolvido um método para caracterização da distribuição de subgrafos e seus inter-relacionamentos. O principal aspecto dessa metodologia é a expansão gradual dos subgrafos, desenvolvida para que os vértices que encontram-se fora de subgrafos possam ter suas relevâncias quantificadas em termos da importância no estabelecimento das conexões entre subgrafos. Experimentos para ilustração do método foram realizados utilizando-se quatro modelos de redes e cinco redes reais, e os resultados obtidos foram relacionados aos processos dinâmicos de transporte e de espalhamento. Outro tópico aqui considerado é o dos efeitos da amostragem de redes corticais, quantificados por meio de análise multivariada e classificação, fazendo uso de um conjunto de medidas estruturais de redes. Esses efeitos também foram mensurados em termos do comportamento dinâmico das redes (sincronização e acessibilidade). Simulações dos métodos de encefalografia MEG e EEG mostraram que as redes amostradas podem apresentar características bem diferentes das da rede original, principalmente no caso de amostras pequenas. Adicionalmente, a rede integrada da bactéria Escherichia coli foi analisada, a qual incorpora (i) regulação de transcrição gênica, (ii) vias metabólicas e de sinalização e (iii) interações entre proteínas. Outliers foram identificados no relacionamento entre grau e atividade, os quais representam reguladores globais de transcrição. Além disso, verificou-se que esses outliers são genes altamente expressos em diferentes condições, apresentando, portanto, uma natureza global no controle de diversos outros genes da célula.The relationship between structure and dynamics was addressed by employing a wide range of different approaches. First, the correlations between degree and activity were studied in various real-world networks. The activity is defined as the proportion of visits to each node in the steady-state regime of the simple random walk. This type of correlation can provide means to assess node activity only in terms of the degree. The concept of accessibility was included in this analysis, showing an intimate relationship (in networks such as the WWW) between the type of correlation and the level of accessibility observed on nodes. A new complex network model founded on growth was also proposed, with new connections being established proportionally to the current activity of each node. This model can be understood as a generalization of the Barabási-Albert model for directed networks. By using several topological measurements we showed that this new model provides, among several other traditional theoretical types of networks, the greatest compatibility with three real-world cortical networks. Additionally, we developed a novel approach considering non-overlapping subgraphs and their interrelationships and distribution through a given network. The main aspect of the methodology is a novel merging procedure developed to assess the relevance of nodes (in relation to the overall subgraph interconnectivity) lying outside subgraphs. Experiments were carried out on four types of network models and five instances of real-world networks, in order to illustrate the application of the method. Furthermore, these results were related to the properties of the transport and spreading processes. Other topic here addressed is the sampling problem in cortical networks. Effects of sampling were quantified using multivariate analysis and classifiers based on structural network measurements. Samples were also evaluated in terms of their dynamical behavior using a synchronization model and the measure of accessibility. By simulating MEG/EEG recordings it was found that sampled networks may substantially deviate from the respective original networks, mainly for small sample sizes. We also report an analysis of the integrated network of Escherichia coli, which incorporates (i) transcriptional regulatory interactions, (ii) metabolic/signaling feedback and (iii) protein-protein interactions. Network outliers, which represent global transcriptional regulators, were identified in the relationship between out-degree and activity. These outliers are highly and widely expressed across conditions, therefore supporting their global nature in controlling many genes in the cell.
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Abdulhameed, Abbas Abdulazeez. "Combining SysML and SystemC to Simulate and Verify Complex Systems". Thesis, Besançon, 2016. http://www.theses.fr/2016BESA2045/document.
Testo completoAbstract (sommario):
De nombreux systèmes hétérogènes sont complexes et critiques. Ces systèmes intègrent du logiciel et des composants matériels avec des interactions fortes entre ces composants. Dans ce contexte, il est devenu absolument nécessaire de développer des méthodologies et des techniques pour spéciier et valider ces systèmes.Dans l'ingénierie des systèmes, les exigences sont l'expression des besoins qu'un produit spécifique ou un service doit réaliser. Elles sont définies formellement à de nombreuses occasions dans l'ingénierie des systèmes complexes. Dans ce type de système, deux catégories d'exigence sont présentes : les exigences non-fonctionnelles telles que la performance et la fiabilité, les exigences fonctionnelles telles que la vivacité. Pour valider ces exigences, un environnement permettant de simuler et vérifier ces propriétés est essentiel.Dans notre travail, nous proposons une méthodologie basée sur SysML et combinée avec SystemC et Promela/SPIN pour spéciier et valider des systèmes complexes. Cette approche est basée sur l'ingénierie dirigée par les modèles pour premièrement traduire des modèles SysML en SystemC afin de réaliser des simulations et deuxièmement traduire des diagrammes d'état SysML en Promela/SPINain de vérifier des propriétés temporelles extraites des exigences. Cette approche est expérimentée sur une étude de cas pour démontrer sa faisabilitéHeterogeneous Systems are complex and become very critical. These systems integrate software andhardware components with intensive interaction between them. In this context, there is a strongnecessity to develop methodologies and techniques to specify and validate these systems.In engineering, the requirements are the expression of needs on what a particular product or a serviceshould be or to make. They are used most of the time in a formal sense in the systems engineering.In this kind of systems, several types of requirements are present: non-functional requirements suchas the performance and the reliability and functional requirements such as the liveliness. To validatethese requirements of a system, an environment to simulate and to check the properties is essential.In our work, we propose a methodology based on SysML combined with SystemC and Promela/SPINto specify and validate complex systems. This approach is based on Model Driven Engineeringtechniques to irstly translate SysML models to systemC with the aim of simulation and to mapSysML behavioral diagrams to Promela/SPIN in order to verify temporal properties extracted fromthe requirements. The approach is experimented on case studies to demonstrate its feasibility
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Carra, Giulia. "Evolution of urban systems : a physical approach". Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS254/document.
Testo completoAbstract (sommario):
Plus de 50% de la population mondiale vit dans des zones urbaines et cette proportion devrait augmenter dans les prochaines décennies. Comprendre ce qui régit l'évolution des systèmes urbains est donc devenu d'une importance fondamentale. Ce renouveau d'intérêt combiné avec la disponibilité de données à grande échelle, permet d'entrevoir l'avènement d'une nouvelle science des villes, interdisciplinaire et basée sur les données.Des études récentes ont montré l'existence de régularités statistiques et de lois d'échelle pour plusieurs indicateurs socio-économiques, tels que la consommation d'essence, la distance moyenne parcourue quotidiennement, le cout des infrastructures, etc. Malgré plusieurs tentatives récentes, la compréhension théorique de ces résultats observés empiriquement demeure très partielle.Le but de cette thèse est d'obtenir une modélisation simplifiée, hors-équilibre de la croissance urbaine, en s'appuyant sur un petit nombre de mécanismesimportants et qui fournit des prédictions quantitatives en accord avec lesdonnées empiriques. Pour cela, nous nous inspirerons des études en géographiequantitative et en économie spatiale et nous revisiterons certains de ces anciens modèles avec une nouvelle approche intégrant les outils et concepts de la physiqueMore than 50 % of the world population lives in urban areas and this proportion is expected to increase in the coming decades. Understanding what governs the evolution of urban systems has thus become of paramount importance.This renewed interest combined with the availability of large-scale data, allows a glimpse into the dawn of a new science of cities, interdisciplinary and based on data.Recent studies have shown the existence of statistical regularities and scaling laws for several socio-economic indicators such as fuel consumption, average commuting distance, cost of infrastructure, etc., and despite several recent attempts, the theoretical understanding of these results empirically observed remains very partial. The purpose of this thesis is to obtain a simplified, out of equilibrium model of urban growth, based on a small number of important mechanisms and which provides quantitative predictions in agreement with empirical data. For this, we will draw on studies in quantitative geography and spatial economy and we will revisit some of these old models with a new approach that integrates the tools and concepts of physics
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Kennedy, Cameron. "Mass media and media complex adaptive systems, towards a complex methodology". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape9/PQDD_0002/MQ43352.pdf.
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Kennedy, Cameron (Cameron John) Carleton University Dissertation Journalism and Communication. "Mass media and media complex adaptive systems; towards a complex methodology". Ottawa, 1999.
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Malada, Awelani. "Stochastic reliability modelling for complex systems". Thesis, Pretoria : [s.n.], 2006. http://upetd.up.ac.za/thesis/available/etd-10182006-170927.
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Wegner, Christopher M. "System-of-systems test planning in a complex joint environment". Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Jun%5FWegner.pdf.
Testo completoAbstract (sommario):
Thesis (M.S. in Operations Research)--Naval Postgraduate School, June 2007.Thesis Advisor(s): Thomas W. Lucas. "June 2007." Includes bibliographical references (p. 65-66). Also available in print.
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Tran, Huy T. "A complex networks approach to designing resilient system-of-systems". Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54384.
Testo completoAbstract (sommario):
This thesis develops a methodology for designing resilient system-of-systems (SoS) networks. This methodology includes a capability-based resilience assessment framework, used to quantify SoS resilience. A complex networks approach is used to generate potential SoS network designs, focusing on scale-free and random network topologies, degree-based and random rewiring adaptation, and targeted and random node removal threats. Statistical design methods, specifically response surface methodology, are used to evaluate SoS networks and provide an understanding of the advantages and disadvantages of potential designs. Linear regression is used to model a continuous representation of the network design space, and determine optimally resilient networks for particular threat types.
The methodology is applied to an information exchange (IE) network model (i.e., a message passing network model) and military command and control (C2) model. Results show that optimally resilient IE network topologies are random for networks with adaptation, regardless of the threat type. However, the optimally resilient adaptation method sharply transitions from being fully random to fully degree-based as threat randomness increases. These findings suggest that intermediately defined networks should not be considered when designing for resilience. Cost-benefit analysis of C2 networks suggests that resilient C2 networks are more cost-effective than robust ones, as long as the cost of rewiring network links is less than three-fourths the cost of creating new links. This result identifies a threshold for which a resilient network design approach is more cost-effective than a robust one.This thesis develops a methodology for designing resilient system-of-systems (SoS) networks. This methodology includes a capability-based resilience assessment framework, used to quantify SoS resilience. A complex networks approach is used to generate potential SoS network designs, focusing on scale-free and random network topologies, degree-based and random rewiring adaptation, and targeted and random node removal threats. Statistical design methods, specifically response surface methodology, are used to evaluate SoS networks and provide an understanding of the advantages and disadvantages of potential designs. Linear regression is used to model a continuous representation of the network design space, and determine optimally resilient networks for particular threat types.
The methodology is applied to an information exchange (IE) network model (i.e., a message passing network model) and military command and control (C2) model. Results show that optimally resilient IE network topologies are random for networks with adaptation, regardless of the threat type. However, the optimally resilient adaptation method sharply transitions from being fully random to fully degree-based as threat randomness increases. These findings suggest that intermediately defined networks should not be considered when designing for resilience. Cost-benefit analysis of C2 networks suggests that resilient C2 networks are more cost-effective than robust ones, as long as the cost of rewiring network links is less than three-fourths the cost of creating new links. This result identifies a threshold for which a resilient network design approach is more cost-effective than a robust one.
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Callantine, Todd Jeffrey. "Tracking operator activities in complex systems". Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/31091.
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Krishan, Kapilanjan. "Characterizations of spatio-temporal complex systems". Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-05162005-071906/.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--Physics, Georgia Institute of Technology, 2006.Schatz, Michael, Committee Chair ; Cvitanovic, Predrag, Committee Member ; Uzer, Turgay, Committee Member ; Grigoriev, Roman, Committee Member ; Mischaikow, Konstantin, Committee Member.
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Sadownik, Jan. "Evolving complex systems from simple molecules". Thesis, St Andrews, 2009. http://hdl.handle.net/10023/857.
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Brusch, Lutz. "Complex Patterns in Extended Oscillatory Systems". Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2001. http://nbn-resolving.de/urn:nbn:de:swb:14-1006416783250-74051.
Testo completoAbstract (sommario):
Ausgedehnte dissipative Systeme können fernab vom thermodynamischen Gleichgewicht instabil gegenüber Oszillationen bzw. Wellen oder raumzeitlichem Chaos werden. Die komplexe Ginzburg-Landau Gleichung (CGLE) stellt ein universelles Modell zur Beschreibung dieser raumzeitlichen Strukturen dar. Diese Arbeit ist der theoretischen Analyse komplexer Muster gewidmet. Mittels numerischer Bifurkations- und Stabilitätsanalyse werden Instabilitäten einfacher Muster identifiziert und neuartige Lösungen der CGLE bestimmt. Modulierte Amplitudenwellen (MAW) und Super-Spiralwellen sind Beispiele solcher komplexer Muster. MAWs können in hydrodynamischen Experimenten und Super-Spiralwellen in der Belousov-Zhabotinsky-Reaktion beobachtet werden. Der Grenzübergang von Phasen- zu Defektchaos wird durch den Existenzbereich der MAWs erklärt. Mittels der selben numerischen Methoden wird Bursting vom Fold-Hopf-Typ in einem Modell der Kalziumsignalübertragung in Zellen identifiziert.