Dissertations / Theses on the topic 'Slow-fast systems'

There are many problems that lead to analysis of dynamical systems with phase variables of two types, slow and fast ones. Such systems are called slow-fast systems. The dynamics of such systems is usually described by means of different versions of perturbation theory. Many questions about accuracy of this description are still open. The difficulties are related to presence of resonances. The goal of the proposed thesis is to establish some estimates of the accuracy of the perturbation theory for slow-fast systems in the presence of resonances. We consider slow-fast Hamiltonian systems and study an accuracy of one of the methods of perturbation theory: the averaging method. In this thesis, we start with the case of slow-fast Hamiltonian systems with two degrees of freedom. One degree of freedom corresponds to fast variables, and the other degree of freedom corresponds to slow variables. Action variable of fast sub-system is an adiabatic invariant of the problem. Let this adiabatic invariant have limiting values along trajectories as time tends to plus and minus infinity. The difference of these two limits for a trajectory is known to be exponentially small in analytic systems. We obtain an exponent in this estimate. To this end, by means of iso-energetic reduction and canonical transformations in complexified phase space, we reduce the problem to the case of one and a half degrees of freedom, where the exponent is known. We then consider a quasi-linear Hamiltonian system with one and a half degrees of freedom. The Hamiltonian of this system differs by a small, ~ε, perturbing term from the Hamiltonian of a linear oscillatory system. We consider passage through a resonance: the frequency of the latter system slowly changes with time and passes through 0. The speed of this passage is of order of ε. We provide asymptotic formulas that describe effects of passage through a resonance with an improved accuracy O(ε3/2). A numerical verification is also provided. The problem under consideration is a model problem that describes passage through an isolated resonance in multi-frequency quasi-linear Hamiltonian systems. We also discuss a resonant phenomenon of scattering on resonances associated with discretisation arising in a numerical solving of systems with one rotating phase. Numerical integration of ODEs by standard numerical methods reduces continuous time problems to discrete time problems. For arbitrarily small time step of a numerical method, discrete time problems have intrinsic properties that are absent in continuous time problems. As a result, numerical solution of an ODE may demonstrate dynamical phenomena that are absent in the original ODE. We show that numerical integration of systems with one fast rotating phase leads to a situation of such kind: numerical solution demonstrates phenomenon of scattering on resonances, that is absent in the original system.

Relaxation oscillations are highly non-linear oscillations, which appear to feature many important biological phenomena such as heartbeat, neuronal activity, and population cycles of predator-prey type. They are characterized by repeated switching of slow and fast motions and occur naturally in singularly perturbed ordinary differential equations, which exhibit dynamics on different time scales. Traditionally, slow-fast systems and the related oscillatory phenomena -- such as relaxation oscillations -- have been studied by the method of the matched asymptotic expansions, techniques from non-standard analysis, and recently a more qualitative approach known as geometric singular perturbation theory. It turns out that relaxation oscillations can be found in a more general setting; in particular, in slow-fast systems, which are not written in the standard form. Systems in which separation into slow and fast variables is not given a priori, arise frequently in applications. Many of these systems include additionally various parameters of different orders of magnitude and complicated (non-polynomial) non-linearities. This poses several mathematical challenges, since the application of singular perturbation arguments is not at all straightforward. For that reason most of such systems have been studied only numerically guided by phase-space analysis arguments or analyzed in a rather non-rigorous way. It turns out that the main idea of singular perturbation approach can also be applied in such non-standard cases. This thesis is concerned with the application of concepts from geometric singular perturbation theory and geometric desingularization based on the blow-up method to the study of relaxation oscillations in slow-fast systems beyond the standard form. A detailed geometric analysis of oscillatory mechanisms in three mathematical models describing biochemical processes is presented. In all the three cases the aim is to detect the presence of an isolated periodic movement represented by a limit cycle. By using geometric arguments from the perspective of dynamical systems theory and geometric desingularization based on the blow-up method analytic proofs of the existence of limit cycles in the models are provided. This work shows -- in the context of non-trivial applications -- that the geometric approach, in particular the blow-up method, is valuable for the understanding of the dynamics of systems with no explicit splitting into slow and fast variables, and for systems depending singularly on several parameters.

Dans ce travail, nous étudions deux types de problèmes à retard. Le premier traite des oscillateurs optoélectroniques (OOEs). Un OOE est un système bouclé permettant de délivrer une onde électromagnétique radio-fréquence de grande pureté spectrale et de faible bruit électronique. Le second problème traite du couplage retardé de neurones. Une nouvelle forme de synchronisation est observée où un régime oscillant est une alternative à un état stationnaire stable. Ces deux problèmes présentent des oscillations de type slow-fast. Une grande partie de ma thèse est dévouée à l’analyse de ces régimes. Etant donné qu’il s’agit d’équations nonlinéaires à retard, les techniques asymptotiques classiques ont dû être revues. En plus d’une étude théorique, des expériences ont été effectuées. Le travail sur les OOEs a été rendu possible grâce aux invitations respectives de L. Larger dans son laboratoire à l’Université de Franche-Comté et de D.J. Gauthier à Duke University. Le travail sur le couplage de neurones a bénéficié d’expériences réalisées par L. Keuninckx du groupe « Applied Physics » de la Vrije Universiteit Brussel.

Une contribution importante de cette thèse est à la fois l’analyse mathématique mais aussi l’observation expérimentale d’ondes carrées stables asymétriques présentant des longueurs de plateau différentes mais ayant la même période dans un OOE. Une bifurcation de Hopf primaire d’un état stationnaire est le mécanisme menant à ces régimes. Un deuxième phénomène qui a été à la fois observé pour l’OOE et pour les neurones couplés est la coexistence entre plusieurs ondes carrées ayant des périodes différentes. Pour l’OOE, ces oscillations peuvent être reliées à plusieurs bifurcations de Hopf primaires qui sont proches les unes des autres à cause du grand délai. Le mécanisme de stabilité est similaire à celui de "Eckhaus" pour les systèmes spatialement étendus. Pour le couplage de cellules excitables, nous avons étudié des équations couplées de type FitzHugh-Nagumo (FHN) linéaires par morceaux et obtenu des résultats analytiques. Nous montrons que le mécanisme menant à ces régimes périodiques correspond à un point limite d’un cycle-limite. La robustesse de ces régimes par rapport au bruit a ensuite été explorée expérimentalement en utilisant des circuits électroniques couplés et retardés. Ce système peut être modélisé mathématiquement par les mêmes équations de type FHN. Pour terminer, nous montrons que les équations pour l’OOE et le FHN possèdent des propriétés similaires. Ceci nous permet de généraliser nos principaux résultats à une plus grande variété d’équations différentielles à retard.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

A critical element to the successful operation of activated sludge systems is efficient solid liquid separation achieved by bioflocculation. Bioflocculation refers to the process of microbial aggregation to form activated sludge flocs, dependent on the interaction of exocellular polymeric substances (EPS) to form the matrix that holds microbes, other organics and inorganic particles in a flocculent mass. Numerous factors affect bioflocculation; two key parameters are the Solid Retention Time (SRT) and the substrate loading rate. The latter is related to the two basic designs in activated sludge bioreactor configurations: the Plug Flow Reactor (PFR) and the Completely Stirred Tank Reactor (CSTR). PFR systems have a high substrate loading rate, whereas CSTRs have a low substrate loading rate. Research has shown that the PFR configurations produce better sludge quality, in terms of settleability and dewaterability, and subsequently better effluent quality than CSTR systems. In this experiment, the effect of SRT and substrate loading rate on activated sludge was investigated using bench scale SBRs. PFR and CSTR configurations were simulated by adjusting the fill period to be shorter or longer respectively. A series of SBRs were operated, each with an operating volume of 6L, to obtain data for PFR (fast feed) versus CSTR (slow feed) configurations at 10 Day, 5 Day and 2 Day SRTs. Effluent quality was monitored by measuring effluent TSS, VSS, total and soluble COD and soluble biopolymers. Sludge quality was monitored for the aerobic phase by measuring total and suspended solids, total and suspended volatile solids, Sludge Volume Index (SVI), Capillary Suction Time (CST) and Zeta Potential. Anaerobic digestibility was measured for the sludge produced in these systems by measuring gas production, similar to estimating biogenic methane potential (BMP) and determining short term odor productions, specifically Total Volatile Organic Sulfur Compounds (TVOSCs). As expected the change in feeding pattern and SRTs affected the effluent and sludge quality during the aerobic operation phase. Effluent quality was found to be better for the fast feed system at all SRTs, with all monitored parameters being of similar or significantly lower concentration than for the slow feed system. In terms of sludge quality, the fast feed system was found to retain more of its biomass in solution, indicating better flocculation and settleability in this system. COD was given a lower rank as an effluent quality indicator, since the 5 Day and 2 Day SRT datasets did not correlate well with other datasets, specifically effluent TSS and biopolymers. The data was included because it is believed that the trends were accurate representations of fast versus slow feed system behavior. The trends were comparable to those of effluent TSS and solution biopolymer datasets. In terms of anaerobic digestion potential, the fast feed sludge exhibited greater volumetric gas production per gram of solid at the 5 and 2 Day SRTs. Gas production was similar for both systems at the 10 Day SRT. Total and Volatile Solid reduction were however found to be higher for the slow feed sludge than for the fast feed. This may indicate higher gas and potential odor production per gram of solid degraded for the fast feed sludge. This theory is supported by the odor analyses, which revealed that the fast feed sludge had a higher TVOSC production at each SRT. This was related to the higher protein content of the sludge, indicated by the effluent biopolymers being much higher in protein content than carbohydrates. Shearing, which is part of the solids handling process at most plants, releases these proteins and makes them bioavailable, allowing them to be oxidized to produce TVOSCs and hence higher odors. In conclusion it was found that the fast feed effluent and sludge quality appeared to be overall better at each SRT simulated; the higher TVOSC content may indicate a problem with solids handling, but research has shown that these can be overcome with the addition of iron. Additionally, both systems, the fast and slow feed systems operated better at longer SRTs, with the fast feed system performing better in all cases. The difference was not completely significant in all cases and this is attributed to being a by-product of operating at the optimal M:D salt ratio. This project has strength in terms of its potential for large scale applications. SRT is the considered the most important design parameter and one of the more complicated parameters to manipulate due to its widespread effect on reactor behavior, specifically sludge and effluent quality. Additionally, the fast feed versus slow feed concept is one that has been gaining significant interest, since bioreactor configuration impacts the effluent and sludge quality. Feed configurations have been investigated more frequently within the past decade. The novel approach taken by this project is that it combines these two parameters, both of which are important to large scale plants, both industrial and municipal.
Master of Science

Philosophiae Doctor - PhD
Numerical approximations of multiscale problems of important applications in ecology are investigated. One of the class of models considered in this work are singularly perturbed (slow-fast) predator-prey systems which are characterized by the presence of a very small positive parameter representing the separation of time-scales between the fast and slow dynamics. Solution of such problems involve multiple scale phenomenon characterized by repeated switching of slow and fast motions, referred to as relaxationoscillations, which are typically challenging to approximate numerically. Granted with a priori knowledge, various time-stepping methods are developed within the framework of partitioning the full problem into fast and slow components, and then numerically treating each component differently according to their time-scales. Nonlinearities that arise as a result of the application of the implicit parts of such schemes are treated by using iterative algorithms, which are known for their superlinear convergence, such as the Jacobian-Free Newton-Krylov (JFNK) and the Anderson’s Acceleration (AA) fixed point methods.

This dissertation seeks to merge the ideas from robust control theory such as H-Infinity control design and the Small Gain Theorem, L stability theory and Lyapunov stability from nonlinear control, and recent theoretical achievements in adaptive control. The fusion of frequency domain and linear time domain ideas allows the derivation of an H-Infinity Norm Minimization Approach (H-Infinity-NMA) for adaptive control architecture that permits a control designer to simplify the adaptive tuning process and tune the uncertainty compensation characteristics via linear control design techniques, band limit the adaptive control signal, efficiently handle redundant actuators, and handle unmatched uncertainty and matched uncertainty in a single design framework. The two stage design framework is similar to that used in robust control, but without sacrificing performance. The first stage of the design considers an ideal system with the system uncertainty completely known. For this system, a control law is designed using linear H-Infinity theory. Then in the second stage, an adaptive process is implemented that emulates the behavior of the ideal system. If the linear H-Infinity design is applied to control the emulated system, it then guarantees closed loop system stability of the actual system. All of this is accomplished while providing notions of transient performance bounds between the ideal system and the true system. Extensions to the theory include architectures for a class of output feedback systems, limiting the authority of an adaptive control system, and a method for improving the performance of an adaptive system with slow dynamics without any modification terms. Applications focus on using aerodynamic flow control for aircraft flight control and the Crew Launch Vehicle.

Dans cette thèse, nous étudions les propriétés de synchronisation d'oscillateurs lents-rapides inspirés de la neuroendocrinologie et des neurosciences, en se concentrant sur les effets des phénomènes de type canard et bifurcations dynamiques sur le comportement collectif.Nous partons d'un système de dimension 4 qui représente les caractéristiques dynamiques qualitatives et quantitatives du profil de sécrétion de la neurohormone GnRH (gonadotropin releasing hormone) au cours d'un cycle ovarien. Ce modèle est constitué de deux oscillateurs de FitzHugh-Nagumo avec pour chacun des échelles de temps différentes. Le couplage unidirectionnel de l'oscillateur lent (représentant l'activité moyenne d'une population de neurones régulateurs) vers l'oscillateur rapide (représentant l'activité moyenne d'une population de neurones sécréteurs) donne une structure à trois échelles de temps. Le comportement de l'oscillateur rapide est caractérisé par une alternance entre un régime de type cycle de relaxation et un régime de quasi-stationnaire qui induit des transitions de type canard dans le modèle ; ces transitions ont un fort impact sur le modèle de sécrétion du système de dimension 4. Nous proposons un premier pas supplémentaire dans la modélisation multi-échelles (en espace) du système GnRH, c'est-à-dire que nous étendons le système original à 6 dimensions en considérant deux sous-populations distinctes de neurones sécréteurs recevant le même signal des neurones de régulation. Cette étape nous permet de enrichir les motifs possibles de sécrétion de GnRH tout en gardant un cadre dynamique compact et en préservant la séquence des événements neuro-sécréteurs capturés par le modèle de dimension 4, à la fois qualitativement et quantitativement.Une première analyse du modèle GnRH étendu à 6 dimensions est présentée dans le Chapitre 2, où nous montrons à l'aide d'un système minimal de dimension 5 l'existence de trajectoires de type canard dans des systèmes lents-rapides couplés présentant des points pseudo-stationnaires. Le couplage provoque la séparation des trajectoires correspondant à chaque sécréteur qui se retrouvent de chaque côté du canard maximal (associé soit à un point pseudo-stationnaire de type noeud soit à un pseudo-col). Nous explorons les rapports entre les canards en présence et le couplage, ainsi que leur impact sur les motifs de sécrétion collective du modèle de dimension 6. Nous identifions deux sources différentes de (dé)synchronisation due aux canards dans les événements sécrétoires, qui dépendent du type de point pseudo-stationnaire sous-jacent.Dans le Chapitre 3, nous proposons une modélisation possible des comportements complexes de sécrétion de GnRH qui ne sont pas capturés par le modèle de dimension 4, à savoir, une décharge avec 2 ``bosses'' et une désynchronisation partielle avant la décharge, en utilisant le modèle de dimension 6 précédemment construit. Pour obtenir une décharge avec deux bosses, il est essentiel d'utiliser des fonctions de couplage asymétriques dépendant du régulateur ainsi que d'introduire de l'hétérogénéité dans les sous-populations de sécréteurs. Pendant le régime pulsatile, il apparaît que le signal régulateur varie lentement et, ce faisant, provoque une bifurcation dynamique qui est responsable de la perte de synchronie dans le cas de sécréteurs non identiques et asymétriquement couplés. Nous introduisons des outils analytiques et numériques pour façonner et quantifier ces caractéristiques supplémentaires et les intégrer dans le profil complet de sécrétion
This dissertation investigates synchronization properties of slow-fast oscillators inspired from neuroendocrinology and neuronal dynamics, focusing on the effects of canard phenomena and dynamic bifurcations on the collective behavior. We start from a 4-dimensional system which accounts for the qualitative and quantitative dynamical features of the secretion pattern of the neurohormone GnRH (gonadotropin releasing hormone) along a whole ovarian cycle. This model involves 2 FitzHugh-Nagumo oscillators with different timescales. Unidirectional coupling from the slow oscillator (representing the mean-field activity of a population of regulating neurons) to the fast oscillator (representing the mean-field activity of a population of the secreting neurons) gives a three timescale structure. The behavior of the fast oscillator is characterized by an alternation between a relaxation cycle and a quasi-stationary state which introduces canard-mediated transitions in the model; these transitions have a strong impact on the secretion pattern of the 4-dimensional system. We make a first step forward in multiscale modeling (in space) of the GnRH system, namely, we extend the original system to 6 dimensions by considering two distinct subpopulations of secreting neurons receiving the same signal from the regulating neurons. This step allows us to enrich further the GnRH secretion pattern while keeping a compact dynamic framework and preserving the sequence of neurosecretory events captured by the 4-dimensional model, both qualitatively and quantitatively. An initial analysis of the extended 6-dimensional GnRH model is presented in Chapter 2, where we prove using a 5D minimal model the existence of canard trajectories in coupled systems with folded singularities. Coupling causes separation of trajectories corresponding to each secretor by driving them to different sides of the maximal canard (associated with either a folded-node or a folded-saddle singularity). We explore the impact of the relationship between canard structures and coupling on the collective secretion pattern of the 6-dimensional model. We identify two different sources of canard-mediated (de)synchronization in the secretory events, which depend on the type of underlying folded singularity. In Chapter 3, we attempt to model complex behaviors of the GnRH secretion not captured by the 4-dimensional model, namely, a surge with 2 bumps and partial desynchronization before the surge, by using the 6-dimensional model previously constructed. Regulatory-dependent asymmetric coupling functions and heterogeneity in the secretor subpopulations are essential for obtaining such a 2-bump surge. During the pulsatile regime, we find that the slowly varying regulatory signal causes a dynamic bifurcation, which is responsible for loss of synchrony in asymmetrically coupled nonidentical secretors. We introduce analytic and numerical tools to shape and quantify the additional features embedded within the whole secretion pattern

Cette thèse s'adresse au problèmes relié au modélisation mathématique en culture continue et culture batch. Nous proposons et étudions, dans une première étape, des modèles mathématiques de quelques processus biologique en culture continue (Chemostat) permettant d'expliquer et de prévoir la coexistence et la coexistence pratique. Dans une deuxième étape, une série d'expériences de laboratoire sont munies en culture batch, et un modèle mathématique tenant compte du recyclage de substrat est proposé, analysé et validé sur des donnés expérimentales en culture pure et mixte prouvant la validité de la principe d'exclusion compétitive en culture batch
Cette thèse s'adresse au problèmes relié au modélisation mathématique en culture continue et culture batch. Nous proposons et étudions, dans une première étape, des modèles mathématiques de quelques processus biologique en culture continue (Chemostat) permettant d'expliquer et de prévoir la coexistence et la coexistence pratique. Dans une deuxième étape, une série d'expériences de laboratoire sont munies en culture batch, et un modèle mathématique tenant compte du recyclage de substrat est proposé, analysé et validé sur des donnés expérimentales en culture pure et mixte prouvant la validité de la principe d'exclusion compétitive en culture batch

Accurate models to reliably predict sediment and chemical transport in watershed water systems enhance the ability of environmental scientists, engineers and decision makers to analyze the impact of contamination problems and to evaluate the efficacy of alternative remediation techniques and management strategies prior to incurring expense in the field. This dissertation presents the conceptual and mathematical development of a general numerical model simulating (1) sediment and reactive chemical transport in river/stream networks of watershed systems; (2) sediment and reactive chemical transport in overland shallow water of watershed systems; and (3) reactive chemical transport in three-dimensional subsurface systems. Through the decomposition of the system of species transport equations via Gauss-Jordan column reduction of the reaction network, fast reactions and slow reactions are decoupled, which enables robust numerical integrations. Species reactive transport equations are transformed into two sets: nonlinear algebraic equations representing equilibrium reactions and transport equations of kinetic-variables in terms of kinetically controlled reaction rates. As a result, the model uses kinetic-variables instead of biogeochemical species as primary dependent variables, which reduces the number of transport equations and simplifies reaction terms in these equations. For each time step, we first solve the advective-dispersive transport of kinetic-variables. We then solve the reactive chemical system node by node to yield concentrations of all species. In order to obtain accurate, efficient and robust computations, five numerical options are provided to solve the advective-dispersive transport equations; and three coupling strategies are given to deal with the reactive chemistry. Verification examples are compared with analytical solutions to demonstrate the numerical accuracy of the code and to emphasize the need of implementing various numerical options and coupling strategies to deal with different types of problems for different application circumstances. Validation examples are presented to evaluate the ability of the model to replicate behavior observed in real systems. Hypothetical examples with complex reaction networks are employed to demonstrate the design capability of the model to handle field-scale problems involving both kinetic and equilibrium reactions. The deficiency of current practices in the water quality modeling is discussed and potential improvements over current practices using this model are addressed.
Ph.D.
Department of Civil and Environmental Engineering
Engineering and Computer Science
Civil Engineering

Ce travail porte sur de nouvelles explosions de cycles (orbites périodiques), l'étude de leur structure par l'analyse qualitative, leur mise en évidence par simulation numérique (Auto, Xpp) et la discussion de leur pertinence dans des modèles mathématiques dans les neurosciences. De telles explosions se produisent dans les systèmes dynamiques lents-rapides. La plupart des neurones sont excitables, dès 1940, Hodgkin identifia trois classes fondamentales d'axones excitables distinguées par leurs réponses à un courant injecté d'amplitude variable. A l'aide de la fonction de Lambert, nous étudions la transition entre les types I et II par des explosions de cycle incomplètes, initiées par une bifurcation de Hopf singulière et qui se terminent dans une bifurcation homocline dans des systèmes une variable rapide/une variable lente. Vient ensuite une étude poussée du système de Hindmarsh-Rose. Il s'agit d'un système deux variables rapides/une variable lente qui produit des oscillations en salves (ou bursting). Nous généralisons la notion d'ensembles candidats-limites-périodiques (clp) aux systèmes tridimensionnels, il s'agit des ensembles invariants du système à la limite singulière. A l'aide de ces derniers, nous obtenons une description très fine de la déformation du cycle limite jusqu'à l'addition d'un nouveau spike au burst. Nous finissons par une étude de la minimalité du modèle de F. Clément et J.-P. Françoise. Ce dernier est un système 4D qui modélise l¿activité des neurones à GnRH. Nous étudions un système une variable rapide/deux variables lentes qui reproduit certaines des caractéristiques du modèle 4D, notamment des Mixed-Modes oscillations
This thesis is focussed on the analysis of novel explosions of limit cycles (periodic orbits). We provide a study of their structure by qualitative analysis, exhibit evidences of their existence by numerical simulations (Auto, Xpp) and propose a discussion of their relevance in mathematical modeling for neurosciences. Such explosions occur in the slow-fast dynamical systems. Most of neurons are excitable, Hodgkin (1940) identified three fundamental classes of excitable axon distinguished by their responses to a current of variable amplitude injected. Using the Lambert function, we study the transition between types I and II by incomplete explosion of cycle. This explosion, produced by a planar vector field with one fast/one slow variable, is initiated by a singular Hopf bifurcation and ends via a homoclinic bifurcation. The next chapter proposed a study of the Hindmarsh-Rose system. This system, composed of one fast/ two slow variables, is well known to produce square wave bursting oscillation. We generalize the notion of candidate-limit-perodic sets (CLP-sets) to three-dimensional systems. A CLP-set is an invariant set of the system in the singular limit. Using these, we get a very acurate description of the limit cycle deformation under the variation of a parameter until the addition of a new spike to burst. Finally, we propose a study fot the minimality of the model introduced by F. Clement and J.-P. Françoise. The latter is a 4D system that models the activity of GnRH neurons. We study a system composed by one fast /two slow variables that reproduces some of the features of the 4D model, including Mixed-Modes oscillations

Orientador: Luiz Fernando Rolim de Almeida
Resumo: A implantação de sistemas de restauração possibilita o restabelecimento da estrutura e funcionamento de ecossistemas degradados. Além disso, alta diversidade taxonômica e funcional dos sistemas de restauração garante a performance e estabilidade de ecossistemas restaurados. A efetividade e monitoramento dos sistemas de restauração são quantificados por variáveis alométricas, porém, desconsideram-se variáveis relacionadas a aquisição de carbono e atividade fotoquímica. Dessa forma, o objetivo deste estudo foi o avaliar as respostas ecofisiológicas de plantas em diferentes sistemas de restauração florestal e avaliar se a capacidade de perda de água e reidratação de espécies de crescimento rápido e lento favorece o estabelecimento e desenvolvimento de sistemas de restauração com estrutura e diversidade de espécies contratantes. Portanto, avaliamos, durante um ano, variáveis relacionadas à disponibilidade de água no solo e ambiente, estrutura dos sistemas de plantio, relações hídricas, atividade fotoquímica e aquisição e acúmulo de carbono nas folhas, em 7 espécies (divididas em espécies de crescimento rápido e lento) pertencentes a três sistemas de restauração: plantio de alta diversidade, sistema agroflorestal e consórcio madeira e lenha, estes sistemas estão implantados em dois tipos de solo: Nitossolo Vermelho (Área 1 – solo argiloso) e Argissolo Vermelho Amarelo (Área 2 – solo arenoso). Os resultados indicaram que sistemas implantados na área 1 apresentaram maior eficiência ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The restoration systems implantation enables the restoration of degraded ecosystems structure and functioning. In addition, restoration systems high taxonomic and functional diversity guarantees restored ecosystems performance and stability. The restoration systems effective-ness and monitoring are quantified by allometric variables, however, variables related to carbon acquisition and photochemical activity are disregarded. Thus, the aim study was to evaluate the ecophysiological responses of plants in different forest restoration systems and to evaluate if the water loss and rehydration capacity of fast and slow growth species favors the establishment and development of systems with contracting structure and species diversity. Therefore, we evaluated, for one year, variables related to the soil and environment water availability, planting systems structure, water relations, photochemical activity and carbon acquisition in leaves, in 7 species (divided into fast and slow growth species). These systems are implanted in two soils types: fertile loamy Ultisol (Site 1) and sandy Alfisol soil (Site 2). The results indicated that systems implanted in site 1 showed higher photosynthetic efficiency and carbon accumulation during water deficiency periods. The wood and wood consortium presented lower complexity in the structure and higher photosynthetic efficiency in times with low water availability in the soil. The mixed plantation using commercial timber and firewood tree species o... (Complete abstract click electronic access below)
Doutor

We study fast-slow versions of the SIR, SIRS and SIRWS epidemiological models, and of the SIRS epidemiological model on homogeneous graphs, obtained through the application of the moment closure method. The multiple time scale behavior is introduced to account for large differences between some of the rates of the epidemiological pathways. Our main purpose is to show that the fast-slow models, even though in nonstandard form, can be studied by means of Geometric Singular Perturbation Theory (GSPT). In particular, without using Lyapunov's method, we are able to not only analyze the stability of the endemic equilibria of the SIR and SIRS models, but also to show that in the remaining models limit cycles arise. We show that the proposed approach is particularly useful in more complicated (higher dimensional) models such as the SIRWS model and the SIRS on homogeneous graphs, for which we provide a detailed description of their dynamics by combining analytic and numerical techniques. In particular, for the latter we show that the model can give rise to periodic solutions, differently from the corresponding model based on homogeneous mixing.

Darbo tikslas: nustatyti skirtingo pobūdžio sveikatą stiprinančių pratybų (jėgos lavinimo pratimų ir šiaurietiško ėjimo) poveikį širdies ir kraujagyslių sistemos greitosios ir lėtosios adaptacijos ypatybėms. Darbo metodika: Darbą sudaro šeši skyriai: literatūros apžvalga, tyrimo organizavimas ir metodika, rezultatai, rezultatų aptarimas, praktinės rekomendacijos bei išvados. Tyrimo metodai: elektrokardiografija (EKG), arterinio kraujo spaudimo (AKS) matavimas, Rufje fizinio krūvio mėginys. Buvo atlikti du tyrimai: I tyrimo metu tirta greitosios adaptacijos poveikis širdies ir kraujagyslių sistemai. II tyrimo metu tirta šešių mėnesių trukmės pratybų sporto salėje ir šiaurietiško ėjimo pratybų įtaka širdies ir kraujagyslių sistemai. Tyrimų metu buvo vertinama širdies ir kraujagyslių sistemos funkcija atliekant Rufje fizinio krūvio mėginį. I tyrimo metu dalyvavo 10 tiriamųjų, kuriems buvo taikytas ir šiaurietiškas ėjimas ir pratybos sporto salėje. II tyrime dalyvavo 28 savanoriai, kurie buvo atsitiktine tvarka suskirstyti į dvi grupes. I-jai grupei buvo taikomas šiaurietiškas ėjimas, II-jai grupei buvo taikomos pratybos prie treniruoklių. Tyrimo išvados: 1. Po pratybų, tiek sporto salėje, tiek po šiaurietiško ėjimo pratybų tiriamiesiems esant santykinės ramybės būsenoje registruojama reikšmingai padidėjęs širdies susitraukimų dažnis (ŠSD), padidėjusios elektrokardiogramos JT/RR santykio reikšmės, ir arterinio kraujo spaudimo rodikliai liudija apie pokrūvinę hipotenziją. Po... [toliau žr. visą tekstą]
The aims of the thesis: to identify the properties of different kinds of health enhancing exercises on the cardiovascular system in fast and slow adaptation. Two studies were performed: Study I investigated quick adaptation effects on the cardiovascular system. Study II investigated the effects of six-month exercise at the gym and Nordic walking exercise on cardiovascular system. The studies were evaluated using the Ruffier exercise test. 10 volunteers participated in Study I; they were subjected to Nordic walking and exercise at the gym. Study II involved 28 volunteers who were randomly divided into two groups. Nordic walking was applied to Group I, while fitness exercises were applied to Group II. The findings of the study: 1. After the exercise and the gym, as well as after Nordic Walking exercise in subjects at rest significantly increased heart rates were recorded, also JT / RR ratio values increased , and arterial blood pressure indicators showed post-load hypotension. After the exercise it was observed that the stress transient ischemic functional effects in the myocardium were less expressed. 2. Comparing Nordic walking exercise effects with the effects of exercise at the gym during the sample load, less increased heart rate and systolic blood pressure were observed; significantly higher decrease in diastolic blood pressure, and significantly lower degree of short-term effects of functional ischemic myocardium were recorded. 3. Six-month health-enhancing exercises... [to full text]

Previous research on human judgment and decision making has demonstrated systematic and predictable biases of judgment in experimental settings. One example of this is the tendency to intuitively violate the conjunction rule - a simple rule of probability. This was well illustrated in the famous Linda-problem. (Tversky & Kahneman, 1983). According to the dual-process theory of reasoning, (Kahneman, 2011) reasoning fallacies such as the conjunction fallacy occurs when people fail to use analytic reasoning and instead overly rely on their intuition. The dual process theory proposes that cognitive processes underlying our intuitive impulses and our conscious reasoning constitutes two different modes in the mind –system 1 and system 2- and that the intuitive system 1 are not able to compute probabilities. Furthermore, it is assumed that processes that are labeled system 1 are fast whereas system 2 are thought to be slow. We tested these time course assumptions of dual process theory in a within-subject design by comparing response time latencies between conjunction fallacy judgments and accurate probability judgments. The results showed that inducing accurate responding did not result in delayed response latency. This indicates that making accurate probability judgments does not require more processing time which goes against what would be expected by the dual-process framework.
Tidigare forskning om mänskligt beslutsfattande och bedömningar har i experiment påvisat systematiska och förutsägbara bias. Ett exempel på detta är tendensen att intuitivt gå emot konjuktionsregeln- en enkel regel gällande sannolikhet. Detta illustrerades väl i det berömda Linda- problemet (Tversky & Kahneman, 1983). Enligt två-systemsteorin (Kahneman, 2011) om problemlösning, uppstår bedömningsfel såsom konjuktionsfelet när människor inte använder sig av analytiskt tänkande och istället förlitar sig för mycket på sin intuition. Två-systemsteorin menar att de kognitiva processer som ligger till grund för våra intuitiva impulser och vårt medvetna resonerande utgör två olika aktörer i vårt tänkande- system 1 och system 2- och att det intuitiva system 1 inte kan beräkna sannolikheter. Processer som betecknas som tillhörande system 1 är enligt två-systemsteorin snabba medan system 2 föreställs vara ett långsamt system. I denna studie testades antagandet om tidsåtgång för de två systemen i en inomgruppsdesign genom att jämföra responstider mellan bedömningar där konjunktionsfelet begåtts och bedömningar där det inte begåtts. Resultaten visar att korrekta sannolikhetsbedömningar inte resulterar i långsammare responstider. Detta indikerar att det inte tycks vara mer tidskrävande att göra riktiga sannolikhetsbedömningar, vilket motsäger två-systemsteorins antagande om snabbt och långsamt processande.

Tout ce qui vit, naît, se nourrit, se reproduit et meurt. Pour le cerveau, la question se complexifie car à la survie des neurones s'ajoute le coût de l'activité cérébrale. La question de la gestion énergétique pour les neurones est particulière car les cellules de notre cerveau évoluent de manière concertée et non par compétition. On sait avec l'imagerie médicale que l'usine neuronale ne fonctionne pas uniquement grâce au glucose ; elle utilise d'autres apports énergétiques tels que le lactate ou le glutamate pour soutenir sa production. Lorsqu'une tumeur apparaît, elle change le métabolisme énergétique pour survivre et soutenir sa propre croissance. En particulier, les cellules cancéreuses se fournissent en lactate et choisissent leur substrat préféré en fonction de l'oxygène disponible. La modélisation mathématique des substrats énergétiques est un outil de choix pour décrire et prédire de tels flux. Coupler ces modèles à des données issues de l'IRM et de la SRM permet d'améliorer la prise en charge du patient présentant un gliome.Cette thèse propose l'approche de plusieurs dynamiques en substrat dans le cerveau sain et gliomateux en se basant sur des systèmes d'équations : échanges locaux en lactate (EDO, système lent-rapide), échanges globaux en substrats (EDO), cycle glutamate/glutamine (EDR) et échanges en lactate en dimensions supérieures (EDP). Ces modèles sont expliqués, décrits grâce aux mathématiques et permettent l'élaboration de simulations ajustées selon des données patient ou issues de la littérature.L'énergie est nécessaire au maintien de la vie. Mais si votre voisin consomme une partie de vos ressources, pouvez-vous encore espérer survivre ?
Everything that lives is born, eats, reproduces and dies. For the brain, the question is more complex because neurons have to survive and to support brain activity. Energy management is also particular because brain cells evolve together with no competition. Thanks to medical imaging, we know that neurons do not consume only glucose. They can use others energetic substrates such as lactate and glutamate as a power source.When a tumor appears, it changes the energetic metabolism to survive and support its own growth. In particular, cancer cells like to consume lactate. They also choose their favorite substrate based on the available oxygen. Modeling of energy substrates is useful to describe and predict energetic kinetics and changes. Mathematical models could get with clinical and medical results to describe, explain or predict low grade glioma dynamics. They can help to characterize and quantify a tumor evolution, then leading to improve their therapeutical management. Exchanges between mathematics and MRI (and MRS) enable to get accurate data and to build suitable mathematical models.This thesis deals with several approaches of substrates dynamics in healthy and gliomatous brains. These researches are based on systems of equations. We model local lactate exchanges (ODE, fast-slow systems), global substrates exchanges (ODE), glutamate/glutamine cycle (RDE) and local lactate exchanges in higher dimensions (PDE). We describe, analyze and give simulations of these models. Simulations are fitted on patient MRI data or literature data. Energy is necessary to live. But if your neighbor consumes a part of your resources, can you still survive ?
Tutto ciò che vive nasce, si nutre, si riproduce e muore. Per il cervello, la questione è più complessa perché i neuroni devono sopravvivere e sostenere l'attività cerebrale. La gestione energetica cerebrale è particolare anche perché le cellule cerebrali evolvono insieme, senza concorrenza. Inoltre, grazie alle immagini mediche, sappiamo che i neuroni non consumano solo del glucosio ma usano altri substrati energetici come il lattato o il glutammato.Quando un tumore si stabilisce, cambia il metabolismo energetico del cervello per sopravvivere e sostenere la propria crescita. In particolare, cellule tumorali consumano del lattato e scelgono il loro substrato preferito basandosi all'ossigeno disponibile.La matematica, e in particolare l'elaborazione di modelli matematici può aiutarci a ottimizzare i dati disponibili, che possono essere, di volta in volta, delle proprietà cellulare o delle lastre MRI o MRS. La modellizzazione dei substrati energetici potrebbe descrivere, spiegare o prevedere le dinamiche energetiche nel cervello.Questa tesi tratta di diversi approcci della dinamica dei substrati nei cervelli sani e gliomatosi. Queste ricerche si basano su sistemi di equazioni. Modellizziamo scambi locali di lattato (ODE, sistemi fast-slow), scambi globali di substrati (ODE), ciclo glutammato/glutammina (RDE) e scambi locali di lattato in dimensioni superiori (PDE). Descriviamo, analizziamo e diamo simulazioni di questi modelli. Le simulazioni sono adeguate su dati MRI paziente o dati di letteratura.Per vivere, l’energia è una necessità. Ma se i Suoi vicini consumassero le Sue risorse, riuscirebbe ancora a sopravvivere ?

Cette thèse porte sur la compréhension des mécanismes de différenciation cellulaire des cellules souches permettant la production des globules rouges (mécanisme appelé érythropoïèse). Nous avons élaboré différents modèles mathématiques permettant une compréhension à différents niveaux. Dans un premier temps, nous avons construit et calibré un modèle à 8 équations différentielles ordinaires pour décrire la dynamique de 6 populations de cellules en érythropoïèse de repos et de stress. L’étude de données expérimentales in vivo, recueillies par nos collaborateurs Stéphane Giraudier (hématologue) et Evelyne Lauret (INSERM), a montré la nécessité d’ajouter deux équations pour modéliser les régulations érythropoïètiques. La calibration du modèle a été effectuée à l’aide des données biologiques et d’un algorithme d’optimisation stochastique appelé CMA-ES. Ce modèle nous a permis de mettre en lumière l’importance de la capacité d’auto-renouvellement des cellules érythropoïètiques dans la production des globules rouges. L’élaboration d’un modèle probabiliste de dimension 3 nous a ensuite permis de comprendre les conséquences dynamiques de cette capacité sur la production des globules rouges. L’étude de ce modèle a nécessité des changements d’échelles en taille et en temps révélant un système dit lent/rapide. À l’aide de méthodes dites de moyennisation nous avons décrit l’approximation en grande population du nombre de cellules de chaque type. Nous avons également quantifié mathématiquement les grandes fluctuations biologiquement observées au niveau du nombre de globules rouges. Nous avons finalement construit un modèle pour comprendre l’influence des longues phases d’inactivité, connues, des cellules souches mutantes dans la production des globules rouges. Les cellules souches mutantes, en faible nombre dans l’organisme comparé aux cellules saines, basculent aléatoirement d’un état actif à un état inactif. Les différences d’échelle de taille entre les populations de cellules, nous a conduit à étudier la dynamique d’un processus de Markov déterministe par morceaux de dimension 4. Nous avons montré l’existence d’une unique probabilité invariante vers laquelle le processus converge en variation totale, et identifié cette limite
This thesis focuses on understanding the mechanisms of stem cell differentiation leading to the production of red blood cells (a mechanism called erythropoiesis). To this end, we have developed different mathematical modelling leading to an understanding at different levels. Firstly, we have built and calibrated a model with 8 ordinary differential equations to describe the dynamics of 6 populations of cells in steady-state and stress erythropoiesis. The study of in vivo experimental data, realized by our collaborators St´ephane Giraudier (hematologist) and Evelyne Lauret (INSERM), showed the need of two equations to model erythropoiesis regulations. Modeling calibration was performed using biological data and a stochastic optimization algorithm called CMA-ES. This model highlighted the importance of the self-renewal capacity of the erythropoietic cells in the production of red blood cells. The development of a 3-dimensional probabilistic model then allowed us to understand the dynamic consequences of this capacity on the production of red blood cells. The study of this model required changes of scale in size and time revealing a so-called slow/fast system. Using averaging methods, we described the large population approximation of the number of each cell type. We have also mathematically quantified the large fluctuations in the number of red blood cells, biologically observed. Finally, we constructed a model to understand the influence of long periods of inactivity of mutant stem cells in the production of red blood cells. Mutant stem cells, which are in low numbers in the organism compared to healthy cells, randomly switch between an active and an inactive state. The different size scale between the cell populations led us to study the dynamics of a 4-dimensional piecewise deterministic Markov process. We showed the existence of a unique invariant probability measure towards which the process converges in total variation, and we identified this limits

Dans le champ du raisonnement, les théories du double processus sont largement reconnues comme expliquant différents phénomènes, tels que les biais décisionnels et le raisonnement moral ou coopératif. Ces théories conçoivent le mode de pensée de l'homme comme une interaction entre un système rapide, automatique et intuitif (Système 1) et un système plus lent et contrôlé (Système 2). Le point de vue dominant sur les double processus et le modèle default-interventionist qui suppose l'existence d'une interaction sérielle entre ces systèmes. Ainsi, quand quelqu'un est affronté à un problème de raisonnement, la réponse de Système 1 se forme initialement. Puis, le Système 2 peut être impliqué dans le processus. Les théories du double processus dominantes postulent que les biais de raisonnement sont le résultat d'une réponse intuitive erronée du Système 1. Selon ces théories le Système 1 est capable de générer des réponses basées sur les indices « heuristiques », tels que les stéréotypes - mais il ne peut pas rendre compte des principes logico-mathématiques. Malgré la grande reconnaissante qu'elle a reçu, cette théorie contient une présomption jamais testée, notamment la présomption « corrective ». Celle-ci postule que dans les situations où les indices heuristiques sont en conflit avec les principes logico-mathématiques, le Système 2 devient obligatoirement impliqué afin de corriger la réponse erronée de Système 1 et ainsi arrive à une réponse utilisant les principes logiques. Il semble donc crucial de tester cette présomption, qui est la question centrale de cette thèse. Dans l’Étude 1, j'ai utilisé des versions modifiées du paradigme de deux réponses afin de tester la présomption corrective utilisant deux problèmes classiques du raisonnement (problèmes de taux de base et de raisonnement syllogistique). Dans ce paradigme, les participants résolvent la même tâche deux fois. D'abord, ils doivent donner une réponse très rapidement. Après, ils font face à la même tâche sans contrainte temporelle. Afin de vérifier que la première réponse est intuitive, on a employé quatre méthodes : des instructions, une charge concomitante, un temps limite de réponse, ainsi que la charge concomitante et le temps limite simultanément. La théorie du double processus prédit que les réponses logiquement correctes n'apparaissent que dans l'étape finale. A contrario, j'ai trouvé que la plupart des participants ayant donné la bonne réponse à l'étape finale l'avaient déjà donnée lors de la phase initiale. Cet effet était présent dans toutes les procédures expérimentales et dans les 2 problèmes de raisonnement. Dans l’Étude 2, j'ai testé la même présomption avec un problème de raisonnement plus difficile, le problème de la « batte-et-balle ». J'ai conduit 7 expériences avec le paradigme de deux réponses et j'ai trouvé que les personnes ayant donné la réponse correcte à la fin l'ont déjà générée lors de la réponse initiale - donc, il semblerait que les participants l'ont fait intuitivement. Ces résultats m'ont amené à réviser le cadre default-interventionist et à proposer une théorie du double processus hybride qui suppose que le Système 1 génère deux différentes réponses intuitives dont une basée sur les principes logico-mathématiques. Ces réponses possèdent une force équivoque au début - celle qui gagnera plus en force sera donnée comme la réponse initiale. J'ai testé les prédictions dérivées de ce modèle via l’Étude 3. Grâce l’Étude 4, j'ai mis au point le modèle hybride en testant les changements de force des réponses intuitives au cours du temps. Au cours de l’Étude 5, j'ai commencé à tester la possibilité de généraliser ce modèle hybride et j'ai étudié si les patterns de réponse étaient similaires lorsque les participants répondent à des dilemmes moraux. Dans l’Étude 6, j'ai utilisé l'EEG afin de retrouver les corrélats neuronaux du traitement logique précoce au cours du raisonnement
Dual-process theories of reasoning have become widely recognized as an explanation for various phenomena, such as thinking biases, moral or cooperative reasoning. Dual-process theory conceives human thinking as the interaction of a fast, more automatic, intuitive system (System 1) and a slower, controlled, more deliberative one (System 2). Arguably, the most dominant view on dual processes is the default-interventionist model. This posits a serial interaction between the two systems. When someone is faced with a reasoning problem, initially a System 1 intuitive response is formed. Then, afterwards, System 2 might get engaged in the process. Prominent dual-process theorists argue that reasoning bias occurs as a result of erroneous System 1 intuition. System 1 is thought to be able to generate responses based on "heuristic" cues, such as stereotypes - and cannot account for logico-mathematical principles. Despite its huge recognition, this theory comes with an untested assumption: the corrective (time-course) assumption. This posits that in cases when heuristic cues are in conflict with logico-mathematical principles, System 2 needs to engage in order to correct initially formed System 1 intuitions, and form a judgement based on logical principles. Testing this assumption is inevitably important and the central question of this thesis. In Study 1, I used four modified versions of the two-response paradigm to test the corrective assumption with two different classical reasoning problems (base rate problems, syllogistic reasoning). In this paradigm, people are presented with the same problem twice. First, they are asked to give an initial, very quick response. After, they are presented with the same problem again and asked to give a final response without any constraints. To make sure that the initial response is really intuitive, we applied four different procedures: instructions, concurrent load, response deadline and load plus deadline. Dual process theory predicts that logically correct responses appear only at the final response stage. Surprisingly, I found that the majority of people who gave the logically correct response in the final response stage already gave it form the beginning. This effect was found to be consistent among all experimental procedures and both reasoning problems. In Study 2, I tried to test the same assumption, with a different -harder- reasoning problem, the bat-and-ball problem. Interestingly, I ran 7 experiments with the two-response paradigm and consistently found that correct reasoners are often able to generate the correct response from the beginning, so-to-say, intuitively. These results forced me to revise the default-interventionist framework and propose the hybrid dual process model. This model now argues that System 1 generates two kinds of intuitive responses one of which is based on mathematico-logical principles. These responses are generated with unequal strength - the one which gains the more strength will be given as the initial response. In Study 3, I directly tested predictions derived from this model. In Study 4, I further developed the hybrid model by testing the changes in the strength of intuitive responses over time. In Study 5, I started to test the hybrid model's domain generality, and test if I find similar patterns of responses when people are faced with moral dilemmas. In Study 6, I used EEG to search for the neural correlates of early logical processing in reasoning. Overall, this thesis found evidence that forces us to revise the traditional dual process view on human reasoning

Relaxation oscillations are highly non-linear oscillations, which appear to feature many important biological phenomena such as heartbeat, neuronal activity, and population cycles of predator-prey type. They are characterized by repeated switching of slow and fast motions and occur naturally in singularly perturbed ordinary differential equations, which exhibit dynamics on different time scales. Traditionally, slow-fast systems and the related oscillatory phenomena -- such as relaxation oscillations -- have been studied by the method of the matched asymptotic expansions, techniques from non-standard analysis, and recently a more qualitative approach known as geometric singular perturbation theory. It turns out that relaxation oscillations can be found in a more general setting; in particular, in slow-fast systems, which are not written in the standard form. Systems in which separation into slow and fast variables is not given a priori, arise frequently in applications. Many of these systems include additionally various parameters of different orders of magnitude and complicated (non-polynomial) non-linearities. This poses several mathematical challenges, since the application of singular perturbation arguments is not at all straightforward. For that reason most of such systems have been studied only numerically guided by phase-space analysis arguments or analyzed in a rather non-rigorous way. It turns out that the main idea of singular perturbation approach can also be applied in such non-standard cases. This thesis is concerned with the application of concepts from geometric singular perturbation theory and geometric desingularization based on the blow-up method to the study of relaxation oscillations in slow-fast systems beyond the standard form. A detailed geometric analysis of oscillatory mechanisms in three mathematical models describing biochemical processes is presented. In all the three cases the aim is to detect the presence of an isolated periodic movement represented by a limit cycle. By using geometric arguments from the perspective of dynamical systems theory and geometric desingularization based on the blow-up method analytic proofs of the existence of limit cycles in the models are provided. This work shows -- in the context of non-trivial applications -- that the geometric approach, in particular the blow-up method, is valuable for the understanding of the dynamics of systems with no explicit splitting into slow and fast variables, and for systems depending singularly on several parameters.

abstract: This thesis describes research into the application of socially reflective, or "Slow", design principles to modern mediated systems, or "Fast" technology. The "information overload" caused by drastic changes in the nature of human communications in the last decade has become a serious problem, with many human-technology interactions creating mental confusion, personal discomfort and a sense of disconnection. Slow design principles aim to help create interactions that avoid these problems by increasing interaction richness, encouraging engagement with local communities, and promoting personal and communal reflection. Three major functional mediated systems were constructed to examine the application of Slow principles on multiple scales: KiteViz, Taskville and Your ____ Here. Each system was designed based on a survey of current research within the field and previous research results. KiteViz is a visually metaphorical display of Twitter activity within a small group, Taskville is a workplace game designed to support collaboration and group awareness in an enterprise, and Your ____ Here is a physical-digital projection system that augments built architecture with user-submitted content to promote discussion and reflection. Each system was tested with multiple users and user groups, the systems were evaluated for their effectiveness in supporting each of the tenets of Slow design, and the results were collected into a set of key findings. Each system was considered generally effective, with specific strengths varying. The thesis concludes with a framework of five major principles to be used in the design of modern, highly-mediated systems that still apply Slow design principles: design for fundamental understanding, handle complexity gracefully, Slow is a process of evolution and revelation, leverage groups and personal connections to encode value, and allow for participation across a widely distributed range of scales.
Dissertation/Thesis
M.S.D. Design 2011

碩士
中華技術學院
電子工程研究所碩士班
96
This paper is performed for the performance analysis of the fast/slow frequency-hopping communication system over the environment of the follower jamming. First, in this paper, we derived the performance of mathematical model of the fast frequency-hopping communications system in the follower/NBN, and the follower/Tone jamming environment. Furthermore, the MATLAB developing tool is used to carry on the numerical analysis of the performance under the different jamming strategy. From the numerical analysis, we proved number of hopping、the dwell time of the follower jamming, and signal to noise ratio are important parameters of the jamming effect. When the number of hopping increases from 1 to 3, the bit error rate may reduce approximately 10 times; In the aspects of dwell time, when jamming dwell increases from 0.1 to 1, the bit error rate can also increase approximately 10 times. Second, we derived the performance of mathematical model of the slow frequency-hopping communications system in the follower/NBN, and the follower/Tone jamming environment. Furthermore, the MATLAB developing tool is used to carry on the numerical analysis of the performance under the different jamming strategy. In general, the jamming strategies that make sense for fast frequency-hopping are not exactly the same as for slow frequency-hopping, therefore in the numerical analysis, the slow frequency-hopping uses the jamming strategies different from fast frequency-hopping. From the numerical analysis, we proved the dwell time of the follower jamming, and signal to noise ratio are important parameters of the jamming effect. When jamming dwell increases from 0.1 to 1, the bit error rate can also increase approximately 10 times.; In the aspects of signal to noise ratio, when signal to noise ratio increases from 15 to 20 , the bit error rate can also decrease approximately 10 times.