Dissertations / Theses on the topic 'Dynamic influence model'

Land carbon sensitivity to atmospheric CO2 concentration (bL) and climate warming (gL) is a crucial part of carbon-climate feedbacks that affect the magnitude of future warming. Although these sensitivities can be estimated by earth system models, their dependence on model representation of land carbon dynamics and the inherent model assumptions has rarely been investigated. Using the widely used Community Land Model version 4 as an example, we examine how bL and gL vary with prescribed versus dynamic vegetation covers. Both sensitivities are found to be larger with dynamic compared to prescribed vegetation on decadal timescale in the late twentieth century, with a more robust difference in gL. The latter is a result of dynamic vegetation model deficiencies in representing the competitions between deciduous versus evergreen trees and tree versus grass over the tropics and subtropics. The biased vegetation cover changes the regional characteristics of carbon-nitrogen cycles such that plant productivity responds less strongly to the enhancement of nitrogen mineralization with warming, so more carbon is lost to the atmosphere with rising temperature. The result calls for systematic evaluations of land carbon sensitivities with varying assumptions for land cover representations to help prioritize development effort and constrain uncertainties in carbon-climate feedbacks.

Static and dynamic interaction mechanism of the retained soil-compressible geofoam buffer and yielding retaining structures requires further investigation. The present study, initiated on this motive, discusses the results of 1-g physical model tests and numerical analyses of cantilever retaining walls with and without deformable geofoam buffers between the wall and cohesionless granular backfill. 0.7m high walls with various wall thicknesses were utilized in the physical modeling. Dynamic tests were carried out by using a laminar container placed on a uni-axial shaking table. Influence of buffer thickness, geofoam type and wall flexibility as well as base excitation characteristics on the lateral earth pressures and flexural wall deflections were under concern. Outcomes of the analyses performed with FLAC-2D (v6.0) finite difference code were validated against the results of the physical model tests. It was observed that the arching effect induced in the retained soil by the lateral compression of the lower half of the geofoam buffer has a positive effect, as this zone is able to absorb a portion of the total unbalanced lateral force exerted by the backfill thus causing a reduction in the static and seismic lateral wall pressures. Relative thickness and stiffness of the geofoam buffer appear to be the most dominant factors affecting the reduction in earth thrust. Lateral earth pressure coefficients determined from physical model tests were compared with those calculated using methods available in the literature. Good agreement was observed between the predictions. Graphs were provided to estimate the static and dynamic lateral earth pressure coefficients for various combinations of wall stiffness and buffer characteristics. Analysis of a 6m high prototype cantilever wall subjected to an excitation recorded in August 17, 1999 Kocaeli earthquake by finite difference method exhibited the contribution of geofoam buffers on seismic performance of cantilever earth retaining walls. It was observed that the presence of an EPS geofoam inclusion provides a reduction of the permanent flexural wall deflections as well as total seismic thrust likely to be experienced by the wall during an earthquake.

PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR
PROGRAMA DE EXCELENCIA ACADEMICA
A estabilidade das colunas de um pórtico plano depende da importância relativa da rigidez à flexão e rigidez lateral de cada coluna e elementos adjacentes. Um exemplo típico é a maior capacidade de carga de pórticos planos com restrição lateral em comparação com pórticos semelhantes, sem restrição lateral. Também esta restrição tem uma influência importante na resposta pós-crítica e na sensibilidade à imperfeição da estrutura. A carga de flambagem pode ser dominada pela rigidez à flexão da coluna ou pela rigidez das restrições laterais. Dependendo dos valores relativos desses parâmetros, pode ocorrer interação modal. Nesse caso, podem surgir vários caminhos pós-críticos, acoplados e desacoplados, levando a uma topologia complexa da energia potencial total com vários pontos críticos (máximos, mínimos e selas). Os caminhos pós-críticos instáveis influenciam na sua capacidade de carga e na sensibilidade da estrutura a imperfeições. Isso leva a um complexo comportamento dinâmico não linear da estrutura carregada axialmente. No presente trabalho, um modelo conceitual de dois graus de liberdade de um elemento de pórtico plano sob compressão é estudado. Uma análise detalhada é realizada a fim de estudar como a rigidez lateral influencia: os comportamentos pré- e pós-crítico, a instabilidade paramétrica do modelo sob uma excitação harmônica axial e o comportamento ressonante do sistema estrutural carregado axialmente sob uma excitação de base; contribuindo para uma melhor compreensão da resposta não linear desta classe de estruturas. A análise das bifurcações mostra que a estrutura pode exibir várias soluções estáveis e instáveis coexistentes, levando a bacias de atração entrelaçadas, cuja topologia controla a integridade dinâmica da estrutura em um ambiente dinâmico. Para estudar o comportamento não linear do modelo, foram utilizadas várias estratégias numéricas para obter os caminhos de equilíbrio não lineares, pontos fixos estáveis e instáveis, diagramas de bifurcação e bacias de atração.
The stability of columns in a portal frame depends on the relative importance of the flexural and lateral stiffness of the column and connected elements. A typical example is the higher load capacity of non-sway frames as compared with that of similar frames with no lateral restrain. Also this restrain has an important influence on the post-critical response and imperfection sensitivity of the structure. The buckling load may be either dominated by the flexural stiffness of the columns or by the stiffness of the lateral restrains. Depending on the relative values of these parameters, interactive buckling may occur. In such case, several coupled and uncoupled post-buckling paths may arise, leading to a complex topology of the energy landscape with several critical points (maxima, minima and saddles). The resulting unstable post-buckling paths influence the structure s imperfection sensitivity and load carrying capacity of the structure. This leads to an involved nonlinear dynamic behaviour of the axially loaded structure. In the present work, a conceptual two-degree-of-freedom model of a plane-frame column is studied. A detailed analysis is conducted to study how the lateral stiffness influences the static buckling and post-buckling behavior, the parametric instability of the model under under axial harmonic excitation and the resonant behavior of the axially loaded structural system under base excitation, contributing to a better understanding of the nonlinear response of this class of structures. The bifurcation analysis shows that the structure may display several coexisting stable and unstable solutions, leading to intertwining basins of attraction, whose topology controls the dynamic integrity of the structure in a dynamic environment. To study the non-linear behavior of the model, several numerical strategies were used to obtain the nonlinear equilibrium paths, stable and unstable fixed points, bifurcation diagrams and basins of attraction.

Understanding how different parameters affect the dynamic response of high-speed railway bridges is crucial to selecting an efficient structural form. Despite existing numerous publications within this field, only few address the importance of torsional deformations. The main objective of this thesis is to investigate the influence of the torsional resistance of the deck on the dynamic response of an existing bridge. Ulla River Viaduct is presented as a case study, allowing to analyse some aspects of its design and what their alteration entails. To this end, 6 different 3D FE models are compared, 5 of which show a modification from the original configuration. In addition, several positions of the train are considered to contrast the effects when the torsional modes are excited. The performed dynamic calculations are based on the implicit direct integration procedure. The analysis of the case study demonstrates the benefit of closing the torsional circuit of the deck. The results also evidence the need of including torsional effects in its dynamic assessment when low values of torsional rigidity are considered. All this is not easy when simplified 2D or 3D beam models are used. As a final remark, the original design of the Ulla River Viaduct is found highly efficient from a dynamical point of view.

[ES] ¿Cómo es la atribución en un entorno de omnicanal? Se puede determinar una distinción importante en contraste con la atribución en un entorno multicanal. Además de proporcionar el proceso de análisis de marketing, una especificación del proceso estándar intersectorial para la minería de datos (CRISP¿DM), se utiliza un enfoque de método mixto secuencial para analizar la cuestión principal de la investigación. En el primer paso de esta investigación se analizan las características y los requisitos de atribución eficiente en un entorno omnicanal. A partir de entrevistas semiestructuradas con expertos y de un proceso de investigación bibliográfica holística estructurada, se identifica claramente la falta de un enfoque de atribución omnicanal. Los enfoques de atribución existentes se identifican mediante la realización de un proceso estructurado de revisión de la literatura. Estos enfoques identificados se evalúan aplicando los resultados de las entrevistas semiestructuradas con expertos, es decir, los requisitos y características de una atribución omnicanal eficiente. Ninguno de los enfoques de atribución identificados cumple con la mayoría de los requisitos de omnicanal analizados. Al tener la brecha de investigación ¿ la falta de un enfoque de atribución de omnicanales ¿ claramente identificada, se desarrolla un enfoque de atribución de omnicanales en la segunda parte de esta investigación presentada. Utilizando la metodología MAP, la principal laguna de investigación se llena proporcionando el Holistic Customer Journey (HCJ): una base de datos lista para el omni¿canal y un enfoque de atribución de omni¿canal correspondiente. Entre otras cosas, el enfoque de atribución desarrollado consiste en una clasificación de aprendizaje automático. Esta investigación presentada es la primera en utilizar información de casi 240.000.000 de conjuntos de datos de interacción, que contienen información entre dispositivos y entre plataformas. Todas las fuentes de datos subyacentes son proporcionadas por una de las plataformas inmobiliarias más grandes de Alemania.
[CAT] Com és l'atribució en un entorn de omnicanal? Es pot determinar una distinció important en contrast amb l'atribució en un entorn multicanal. A més de proporcionar el procés d'anàlisi de màrqueting, una especificació del procés estàndard intersectorial per a la mineria de dades (CRISP¿DM), s'utilitza un enfocament de mètode mixt seqüencial per analitzar la qüestió principal de la investigació. En el primer pas d'aquesta investigació s'analitzen les característiques i els requisits d'atribució eficient en un entorn omnicanal. A partir d'entrevistes semiestructurades amb experts i d'un procés de recerca bibliogràfica holística estructurada, s'identifica clarament la falta d'un enfocament d'atribució omnicanal. Els enfocaments d'atribució existents s'identifiquen mitjançant la realització d'un procés estructurat de revisió de la literatura. Aquests enfocaments identificats s'avaluen aplicant els resultats de les entrevistes semiestructurades amb experts, és a dir, els requisits i característiques d'una atribució omnicanal eficient. Cap dels enfocaments d'atribució identificats compleix amb la majoria dels requisits de omnicanal analitzats. En tenir la bretxa de recerca ¿ la manca d'un enfocament d'atribució de omnicanales ¿ clarament identificada, es desenvolupa un enfocament d'atribució de omnicanales a la segona part d'aquesta investigació presentada. Utilitzant la metodologia MAP, la principal llacuna de recerca s'omple proporcionant el Holistic Customer Journey (HCJ): una base de dades a punt per al omni¿canal i un enfocament d'atribució de omni¿canal corresponent. Entre altres coses, l'enfocament d'atribució desenvolupat consisteix en una classificació d'aprenentatge automàtic. Aquesta investigació presentada és la primera a utilitzar informació de gairebé 240.000.000 de conjunts de dades d'interacció, que contenen informació entre dispositius i entre plataformes. Totes les fonts de dades subjacents són proporcionades per una de les plataformes immobiliàries més grans d'Alemanya.
[EN] What does attribution in an omni¿channel environment look like? A major distinction can be determined in contrast to attribution in a multi¿channel environment. Besides providing the Marketing Analytics Process, a specification of the Cross¿industry standard process for data mining (CRISP¿DM), a sequential mixed method approach is utilized to analyze the main research question. Within the first step of this presented research characteristics, and requirements of efficient attribution in an omni¿channel environment are analyzed. Based on semi¿structured expert interviews and a holistic structured literature research process, the lack of an omni¿channel attribution approach is clearly identified. Existing attribution approaches are identified by conducting the structured literature review process. Those identified approaches are evaluated by applying the results of the semi¿structured expert interviews - the requirements and characteristics of efficient omni¿channel attribution. None of the identified attribution approaches fulfill a majority of the analyzed omni¿channel requirements. By having the research gap - the lack of an omni¿channel attribution approach - clearly identifed, an omni¿channel attribution approach is developed in the second part of this presented research. Utilizing the MAP methodology, the main research gap is filled by providing the Holistic Customer Journey (HCJ): an omni¿channel ready data foundation and a corresponding omni¿channel attribution approach. Among other things the developed attribution approach consists of a machine learning classification. This presented research is the first to utilize information from almost 240.000.000 interaction data sets, containing crossdevice and cross¿platform information. All underlying data sources are provided by one of Germany's largest real¿estate platforms.
Nass, O. (2019). Optimizing Online Marketing Efficiency By Analyzing the Mutual Influence of Online Marketing Channels with Respect to Different Devices [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/122296
TESIS

Les travaux effectués dans le cadre de cette thèse portent sur la modélisation et la compréhension du comportement des structures en béton soumises à des chargements de type cyclique et dynamique. Le programme expérimental camus (maquette de bâtiment a échelle 1/3), réalisé sur la table sismique du CEA-Saclay, nous a permis, par une confrontation avec des simulations numériques, de mettre en avant les deux points sensibles du calcul que sont : la prise en compte physique des phénomènes d'amortissement ainsi que la détermination objective d'un critère de ruine sur structure. Afin d'améliorer la prédiction des calculs numériques, le présent travail tente de diminuer l'importance d'une matrice globale d'amortissement au profit d'une représentation locale des dissipations. Ainsi l'hystérésis du matériau, dérivant du frottement entre lèvres de fissures, est décrite par un couplage entre le niveau d'endommagement et la présence de contraintes de frottement sur les plans de décohésion. Ce modèle local, établi dans le cadre de la thermodynamique des processus irréversibles, permet de relocaliser la dissipation dans les zones sollicitées et de la corréler au niveau de fissuration. L'implantation numérique du modèle a été réalisée dans un code ef de type poutre multicouches et validée sur des essais de flexion 3 points sur poutres en béton arme. La prise en compte d'un critère de ruine nous a conduits à la question de la localisation des déformations dans des contextes de dynamique lente et rapide. Dans ce but, un modèle visco-endommageable a été implante dans un code de dynamique explicite tridimensionnel permettant de traiter ce problème pour des chargements a grande vitesse de déformation.

As the human population grows, so too does the need to understand human behavior. One particularly important aspect of human behavior is how it changes within conglomerations of people, i.e. crowds. In this thesis, a method for modeling crowd behavior is proposed. This method draws inspiration from the concept of behavioral intention and the related forces of attitudes, influences, and social norms. These topics are first defined and detailed, followed by a survey of related research. Next, the model is presented and adapted to three common crowd dynamics, each stressing a different component of behavioral intention. Observations are made about these models, and extensions to the models and directions for future research are considered.

Infrastructure management must move from a perspective that may singularly emphasize facility condition assessment to a broader view that involves nonphysical factors, which may substantially impact facility performance and shorten its service life. Socioeconomic, technological, regulatory, and user value changes can substantially increase the service expectations of existing facilities. Based on a theoretical framework drawn from prior work, this research develops a new approach to model infrastructure performance and assess factors that influence the remaining service life of highway bridges. Key parameters that impact the serviceability of highway bridges are identified and incorporated into a system dynamics model. This platform supports parametric scenario analysis and is applied in several cases to test how various factors influence bridge service life and performance. This decision support system provides a new approach for modeling serviceability over time and gives decision-makers an indication of: (a) the gap between society's service expectations and the service level provided and (b) the remaining service life of a highway bridge.
Ph. D.

In this work the influence of Under Sleeper Pads on the dynamic forces on a railway track is investigated. A special interest is devoted to the effect of using Under Sleeper Pads in a railway track with changing vertical stiffness. The contact force between wheel and rail and the ballast contact forces are examined. For the investigation a finite element model with the length of thirty sleepers is created and calculations are performed with the software LS-DYNA. Three different cases of varying vertical track stiffness are studied: the transition from an embankment to a bridge, a randomly varying track stiffness along the railway track and hanging sleepers.

Analyse des consequences du refroidissement des racines sur la croissance et le developpement du dactyle en phase vegetative permettant l'etude du fonctionnement de la plante entiere en rapport avec la contrainte hydrique et la nutrition minerale

Cette thèse étudie les causes et conséquences du processus de ségrégation résidentielle dans l’Afrique du Sud (AFS) post-Apartheid. Nous nous intéressons à plusieurs aspects encore débattus dans la littérature. Le premier concerne l’impact des préférences des individus pour la composition raciale de leur voisinage sur la ségrégation. Le second a trait à l’impact de la ségrégation résidentielle sur les niveaux de revenus des différents groupes raciaux. Le dernier quantifie les différentes causes de la ségrégation. Dans le premier chapitre, nous réconcilions la littérature théorique sur l’impact des préférences pour la composition raciale du voisinage avec les observations empiriques de niveaux décroissants de ségrégation aux US et en AFS. Nous soutenons l’idée que si les individus internalisent les apports économiques et sociaux de chaque nouvel arrivant dans leur voisinage alors des voisinages intégrés peuvent émerger. Cet effet est empiriquement plus fort que l’homophilie et le racisme. Dans le second chapitre, nous étudions l’impact de la ségrégation sur l’ensemble de la distribution des revenus. Nous montrons que la ségrégation a un effet positif sur les hauts revenus pour les Blancs tandis qu’elle a un effet négatif pour les Noirs au bas de la distribution. L’effet de la ségrégation est souvent plus important que l’effet de l’éducation. Enfin, dans le troisième chapitre, nous quantifions l’impact de chaque déterminant de la ségrégation. Nous trouvons que le manque d’accès aux services publics de base est le déterminant principal, alors que les différences de caractéristiques sociodémographiques ne comptent que pour une faible part pour les quartiers les plus ségrégués
This thesis studies the causes and consequences of the residential segregation process in the post-Apartheid South Africa.Inside this general issue, we are interested in several aspects still debated in the literature on residential segregation. Thefirst concerns the impact of individuals’ preferences for the racial composition of their neighborhood on the segregationlevels. The second question deals with the impact of residential segregation on the income levels of each racial group. Thelast issue is related to quantifying the different causes of segregation.Three chapters constitute this thesis. In the first chapter, we reconcile the theoretical literature on the impact of preferencesfor the racial composition of the neighborhood with the empirical evidences of declining levels of segregation in theUnited-States and South Africa. We argue that if individuals internalize the economic and social life that a new entrantbrings with him, then integrated neighborhoods can emerge. This effect is empirically stronger than homophilly andracism. In the second chapter, we study the impact of residential segregation on the whole income distribution. We showthat residential segregation has a positif effect on top incomes for Whites, whereas it has a negatif effect for Blacks at thebottom of the distribution. The effect of residential segregation is even more important than the effect of education inmost cases. In the third chapter, we quantify the impact of each determinant of segregation. We find that the lackof access to basic public services is the main determinant, whereas differences in sociodemographics only account for asmall part in the most segregated areas

Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.
Includes bibliographical references (p. 186-188).
In this thesis we introduce and analyze the influence model, a particular but tractable mathematical representation of random, dynamical interactions on networks. Specifically, an influence model consists of a network of nodes, each with a status that evolves over time. The evolution of the status at a node is according to an internal Markov chain, but with transition probabilities that depend not only on the current status of that node, but also on the statuses of the neighboring nodes. Thus, interactions among the nodes occur probabilistically, starting when a change of status at one node alters the transition probabilities of its neighbors, which then alter those of their neighbors, and so on. More technically, the influence model is a discrete-time Markov process whose state space is the tensor product of the statuses of all the local Markov chains. We show that certain aspects of the dynamics of the influence model can be studied through the influence matrix, a reduced-order matrix whose dimension is the sum rather than the product of the local chain dimensions. We explore the eigenstructure of the influence matrix and explicitly describe how it is related to that of the full-order transition matrix. From the influence matrix, we also obtain the influence graph, which allows the recurrent states of the influence model to be found by graph-theoretic analysis on the reduced-order graph. A nested hierarchy of higher-order influence matrices, obtained from Kronecker powers of the first-order influence matrix, is exposed. Calculations on these matrices allow us to obtain progressively more elaborate statistics of the model at the expense of progressively greater computational burden. As a particular application of the influence model, we analyze the "to link or not to link" dilemma. Suppose that a node is either in a 'healthy' or 'failed' status. Given that connecting to the network makes its status dependent on those of its neighbors, is it worthwhile for a node to connect to the network at all? If so, which nodes should it connect to in order to maximize the 'healthy' time? We formulate these questions in the framework of the influence model, and obtain answers within this framework. Finally, we outline potential areas for future research.
by Chalee Asavathiratham.
Ph.D.

Innovation is fundamental to long-term business success in technology medium-sized enterprises (MSEs). The owner-CEO interrelationship is likely to set the culture and be an important influence on the enterprise innovation capability. Previous studies of the owner-CEO interrelationship have produced varying results but few have examined the influence on innovation capability. Agency theory assumes that owners and CEOs have contrasting objectives but it is silent when owners and CEOs are in accord. Companies may have varying dominant ideologies, such as entrepreneurialism, managerialism, and paternalism, which likely influence their innovation capability. Using primary data from three different German MSEs, selected for their contrasting ideologies, this study examines how interrelationship influences of the owner-CEO interrelationship have the potential to influence the innovation capability of MSEs. The results show that the influence of the owner-CEO interrelationship on the innovation capability is associated with social and situational influences. This thesis provides an original contribution by developing an “interrelationship influence model” that captures the interrelationship factors that influence innovation capability, namely: action, support, communication, responsibility, power and autonomy. This study has important implications for researchers in corporate governance as well as in innovation. Enterprises aiming to improve their innovation capability should pay attention to interrelationships and the influence of owners as well as to the CEO and the management team.

As ever-increasing levels of carbon dioxide alter the chemistry of the Earth’s atmosphere, understanding the global carbon cycle becomes increasingly important. A particularly important component is the riverine carbon cycle, as rivers are the primary conduits for dissolved inorganic carbon from terrestrial watersheds to ocean basins. Stable carbon isotopes (13C/12C) were collected weekly and input into the mixing model IsoSource to delineate seasonal carbon sourcing along two nested basins in the upper Green River System, Kentucky. In the more siliciclastic upstream catchment, dissolved inorganic carbon (DIC) was primarily derived from soil respiration (34%). Groundwater dissolving carbonate bedrock and carbonate dissolution/precipitation reactions contributed 31% and 11%, respectively. The more carbonate-dominated downstream catchment also was influenced greatly by soil respiration (35%). Due to the more pronounced levels of carbonate bedrock, carbonate reactions contributed double that of the upstream catchment (20%), with groundwater contributing 22%. Seasonally, the upstream basin gathered most DIC from soil respiration from late spring to winter. Early spring precipitation and still limited photosynthesis caused the primary carbon sourcing to shift to groundwater. Downstream, the primary source throughout the entire study period was soil respiration. Collectively, this study provides insight into the carbon cycling process in a mid-latitude, karstic river using carbon isotope sourcing to aid in the quantification of global carbon flux in the critical zone.

Since the wave of civil violence in the USA in the 1960s, many social theorists have tried to explain why riots occur. Despite at least 50 years of research since then, there is still not enough insight to anticipate large events like the 2011 Arab Spring and London riots. The main goal of this thesis is therefore to improve understanding about how underlying conditions influence and drive riot dynamics, such as the intensity, spread, and duration. I develop a new mechanistic and stochastic agent-based model for riots. Previous models have either only targeted general phenomena associated with riots, or aimed at behaviour specific to a single event. In this thesis I combine both approaches: I demonstrate how the model in which the motivation of the agents is based on general concepts, can be applied to the specific situation of the 2011 London riots. The model reproduces the majority of the behaviour observed in the London riots (r = 0.4-0.8). One of the key factors under investigation is the relationship between protests and outbursts of civil violence. Riots are often preceded by protests, such that a large pool of potential rioters is directly available. I find that the number of times a protest is repeated has greater influence on riot dynamics than the protest crowd size. The support shown during demonstrations might incite false confidence in individuals, potentially leading to quicker escalation. Another question is how contact networks and collective identity influence the spread of violence between different locations. The role of online social media (e.g. Twitter) has been a major focus in trying to explain why the violence in the 2011 Arab spring spread so quickly and so far. I investigate the role of social similarity as another factor that might have contributed to the diffusion of unrest, and demonstrate the existence of a critical transition in riot activity when increasing the density of the contact network in the model. Such increases in density beyond the critical thresholds might have been introduced by online social networks. Finally, I explore the sensitivity to cooperation of different potential riot groups. In some cases, mixed populations with different collective identities can form coalitions within neighbourhoods based on shared grievances, which could lead to increases in riot size and riot probability. I examine the influence of the social structure and spread of these populations over different neighbourhoods, as well as the overlap in grievances and different demographic structures.

Developing a robust pipe leak monitoring tool is essential as it continuously monitors pipeline health without disrupting normal operation. It is critical to understand the physical phenomena in the leakage area to develop a robust pipeline condition monitoring. This research project provides a better understanding of pipe leakage fluid dynamics and their influences on acoustic emission signal generation. The findings obtained from this project lay the groundwork for the development of a robust pipeline condition monitoring technique that could be implemented without disrupting normal operation. Such a monitoring tool would have significant financial, environmental, and social benefits.

Systematic parametric studies were performed to better understand seal-inlet rotordynamics. A CFD-perturbation model was employed to compute the seal-inlet flow disturbance quantities. Seal inlet disturbance boundary condition correlations were proposed from the computed seal-inlet quantities using the important parameters. It was found that the cosine component of the seal-inlet swirl velocity disturbance W1C has a substantial impact on the cross-coupled stiffness, and that the correlations for W1C and W1S should be used to replace the historical guess that seal inlet W1C = 0 and W1S = 0. Also, an extremely precise relationship was found between the swirl disturbance W1C and the seal-inlet swirl velocity (ωRsh − ¯W0). Thus, the number of experiments or computer runs needed to determine the effect of spin speed, shaft radius and/or inlet swirl velocity on the cross-coupled stiffness is greatly reduced by plotting the simplified relationship of the cross-coupled stiffness against the swirl slip velocity. The benefits of using the new seal-inlet boundary condition correlations were assessed by implementing them into a CFD-perturbation model. Consistently improved agreement with measurements was obtained for both liquid annular seals and gas labyrinth seals. Further, the well-established CFD-perturbation model with new boundary condition correlations was employed to investigate the rotordynamics of two off-design situations. The first case considered the influence of labyrinth seal teeth damage on the performance and the rotordynamic characteristics of impeller eye seals in centrifugal compressors. The second case considered the influence of rotor-axial-shifting on rotordynamic forces for high-low labyrinth seals in steam turbines during the start-up and shut-down process. The results should provide useful information for labyrinth seal design and fault diagnosis of stability problems in turbines and compressors.

The present work is concerned with projective prepositions, which express the relation between two objects by referring to a direction in three-dimensional space. The projective prepositions have been regarded as expressing simple schematic relations of a geometric nature. A theory of the apprehension of projective relations can account for their meanings when they express strictly geometric relations. However, many studies have shown that the appropriateness of the prepositions also depends on the functional relation between the objects and that a number of functional factors influence the comprehension of English prepositions. This experimental study investigates if the acceptability of the Swedish prepositions över, under, ovanför and nedanför are influenced by functional factors as well, and whether acceptability judgments about över and under are more sensitive to functional influences than judgments about ovanför and nedanför, as has been shown for the corresponding English prepositions over and under, and above and below, respectively. It also investigates how the shapes and the parts of the related objects influence their functional interaction, and how the acceptability of the prepositions is in consequence influenced by the shapes of the objects. It was found that the theory of apprehension can indeed account for the acceptability of the prepositions when the relation between the objects is strictly geometric. It was further found that acceptability judgments about them are influenced by functional factors in a similar manner to the corresponding English prepositions when the objects are functionally related, although judgments about under and nedanför are not differentially influenced by these factors. Furthermore, the shapes and the parts of both of the related objects influence acceptability judgments about the prepositions in predictable manners. An extension of the theory of apprehension is suggested which can account for the functional influences indicated in the present study.

Dynamic simulation models of three nested North Pacific ecosystems (the Strait of Georgia, the British Columbia Shelf and the Northeast Pacific) were constructed to examine how area scale affects modelled historic changes of trophic interactions, fisheries and climate. Species groups were the same for all ecosystem models, with a focus upon commercially important fish species. The models were dynamic and spanned the period from 1950 to the start of the 21st Century. Time series data for biological indicators were compared to predicted model time series, under different scenarios of ecosystem control: top-down, bottom-up, or combinations thereof. Results of these scenarios suggest that while fisheries, and predation / competition effects explain most population changes for commercially important fish species, all species modelled also appear to experience bottom-up effects driven by climate change, and regime shifts. The ecosystem models suggest such bottom-up dynamics through predicted primary production anomalies similar to decadal cycling seen in climate indices like the Pacific Decadal Oscillation (Northeast Pacific), upwelling at 54°N (BC shelf) and Salinity / Fraser River discharge (Strait of Georgia). The results of this work suggest that both the area and scale over which indices of regime shifts and climate change are measured are linked, via bottom-up forcing, to changes in biomasses of all trophic levels in these ecosystems. The ability to link bottom-up and top-down dynamics provides an exciting way for ecosystem models to contribute to the formulation of policy and cross validation of single species stock assessment research.
Science, Faculty of
Resources, Environment and Sustainability (IRES), Institute for
Graduate

Marine sediments are a key component of the global carbon cycle and climate system. They host one of the largest carbon reservoirs on Earth, provide the only long-term sink for atmospheric CO2, recycle nutrients and represent the most important climate archive. Early diagenetic pro- cesses in marine sediments are thus central to our understanding of past, present and future biogeochemical cycling and climate. Because all early diagenetic processes can be directly or indirectly linked back to the degradation of organic matter (OM), advancing this understand- ing requires disentangling the different factors that control the fate of OM (sedimentation, degradation and burial) on different spatial and temporal scales. In general, the heterotrophic degradation of OM in marine sediments is controlled by the quantity and, in particular, by the ap- parent reactivity of OM that settles onto marine sediments. While the potential ((micro)biological, chemical and physical) controls on OM reactivity are increasingly well understood, their relative significance remains difficult to quantify. Traditionally, integrated data-model approaches are used to quantify apparent OM reactivity (i.e. OM degradation rate constants) at well-studied drill-sites. These approaches rely on Reaction-Transport Models (RTMs) that typically account for transport (advection, molecular diffusion, bioturbation, and bioirrigation) and reaction (pro- duction, consumption, equilibrium) processes, but vary in complexity. Apparent OM reactivity (i.e. the OM degradation rate constant) is generally considered as a free parameter that is used to fit observed depth-profiles, reaction rates or benthic-pelagic exchange fluxes. Currently, no quantitative framework exists to predict apparent OM reactivity in areas where comprehensive benthic data sets are not available.To evaluate the impact of this knowledge gap, the sensitivity of benthic biogeochemical reaction rates, as well as benthic-pelagic exchange fluxes to variations in apparent OM reactivity (i.e. reactive continuum model parameters a and ν) is explored by means of a complex, numerical diagenetic model for shelf, slope and deep sea depositional environments. Model results show that apparent OM reactivity exerts a dominant control on the magnitude of biogeochemical reaction rates and benthic-pelagic exchange fluxes across different environments. The lack of a general framework to quantify OM reactivity thus complicates the parametrization of regional and global scale diagenetic models and, thus, compromises our ability to quantify global benthic-pelagic coupling in general and OM degradation dynamics in particular.To make a first step towards an improved systematic and quantitative knowledge of OM reac- tivity, apparent OM reactivity (i.e. reactive continuum model parameters a and ν) is quantified by inverse modelling of organic carbon, sulfate (and methane) sediment profiles, as well as the location of the sulfate-methane transition zone using a complex, numerical diagenetic model for 14 individual sites across different depositional environments. Model results highlight again the dominant control of OM reactivity on biogeochemical reaction rates and benthic exchange fluxes. In addition, results show that, inversely determined ν-values fall within a narrow range (0.1 < ν < 0.2). In contrast, determined a-values span ten orders of magnitude (1 · 10−3 < a < 1·107) and are, thus, the main driver of the global variability in OM reactivity. Exploring these trends in their environmental context reveals that apparent OM reactivity is determined by a dynamic set of environmental controls rather than traditionally proposed single environmental controls (e.g. water depth, sedimentation rate, OM fluxes). However, the high computational demand associated with such a multi-species inverse model approach, as well as the limited availability of comprehensive pore water data, limits the number of apparent OM reactivity estimates. Therefore, while providing important primers for a quantification of OM reactivity on the global scale, inverse model results fall short of providing a predictive framework.To overcome the computational limitations and expand the inverse modelling of apparent OM reactivity to the global scale, the analytical model OMEN-SED is extended by integrating a nG- approximation of the reactive continuum model that is fully consistent with the general structure of OMEN-SED. The new version OMEN-SED-RCM thus provides the computational efficiency required for the inverse determination of apparent OM reactivity (i.e. reactive continuum model parameters a and ν) on the global scale. The abilities of the new model OMEN-SED-RCM in capturing observed local, as well as global patterns of diagenetic dynamics are rigorously tested by model-data, as well as model-model comparison.OMEN-SED-RCM is then used to inversely determine apparent OM reactivity by inverse modelling of 394 individual dissolved oxygen utilisation (DOU) rate measurements. DOU is commonly used as a proxy for OM reactivity, it is more widely available than comprehensive porewater data sets and global/regional benthic maps of dissolved oxygen utilisation rates (DOU) have been derived based on the growing DOU data set. Sensitivity test show that, while inverse modelling of DOU rates fails to provide a robust estimate of RCM parameter ν, it is a good indicator for RCM parameter a. Based on previous findings, parameter ν was thus assumed to be globally constant. Inversely determined a-values vary over order of magnitudes from a = 0.6 years in the South Polar region to a = 5.6 · 106 in the oligotrophic, central South Pacific. Despite a high intra- as well as interregional heterogeneity in apparent benthic OM reactivity, a number of clear regional patterns that broadly agree with previous observations emerge. High apparent OM reactivities are generally observed in regions dominated by marine OM sources and characterized by efficient sinking of OM and a limited degradation during sinking. In contrast, the lowest apparent OM reactivities are observed for regions characterized by low marine primary production rates, in combination with a great distance to the continental shelf and slope, as well as deep water columns. Yet, results also highlight the importance of lateral transport processes for apparent OM reactivity. In particular, deep sea sediments in the vicinity of dynamic continental margin environments or under the influence of strong ocean currents can receive comparably reactive OM inputs from more productive environments and, thus, reveal OM reactivities that are higher than traditionally expected. Finally, based on the observed strong link between apparent OM reactivity (i.e. RCM parameters a) and DOU rate, a transfer function that predicts the order of magnitude of RCM parameter a as a function of DOU is used to derive, to our knowledge, the first global map of apparent OM reactivity.Finally, we use the new global map of apparent OM reactivity to quantify biogeochemical dynamics and benthic-pelagic coupling across 22 benthic provinces that cover the entire global ocean. To this end, the numerical diagenetic model BRNS model is set-up for each province and forced with regionally averaged boundary conditions derived from global data sets, as well as apparent OM reactivities informed by the global OM reactivity map. The 22 regional model set-ups were then used to quantify biogeochemical process rates, as well as benthic carbon and nutrient fluxes in each province and on the global scale. Model results of regional and global fluxes and rates fall well within the range of observed values and also agree with general globally observed patterns. Results also highlight the role of the deeper ocean for benthic-pelagic cycling and indicate towards a large regional variability in benthic cycling at great depth. This is a first step towards a more refined global estimate of benthic biogeochemical cycling that accounts for the global heterogeneity of the seafloor environment. This aspect is critical to improve our understanding of benthic feedbacks on benthic-pelagic coupling and on the carbon-climate system, which can then be incorporated in benthic processes in Earth System Models.
Les sédiments marins sont un élément clé du cycle mondial du carbone et du système climatique. Ils abritent l’un des plus grands réservoirs de carbone sur Terre, fournissent le seul puits à long terme pour le CO2 atmosphérique, recyclent les nutriments et constituent les archives climatiques les plus importantes. Les processus de la diagénèse précoce dans les sédiments marins sont donc au cœur de notre compréhension des cycles et du climat biogéochimiques passés, présents et futurs. Étant donné que tous les processus diagénétiques précoces peuvent être directement ou indirectement liés à la dégradation de la matière organique (MO), faire progresser cette compréhension nécessite de démêler les différents facteurs qui contrôlent le devenir de la MO (sédimentation, dégradation et enfouissement) à différentes échelles spatiales et temporelles. En général, la dégradation hétérotrophique de la MO dans les sédiments marins est contrôlée par la quantité et, en particulier, la réactivité apparente de la MO qui se dépose sur les sédiments marins. Bien que les contrôles potentiels ((micro) biologiques, chimiques et physiques) de la réactivité de la MO soient de mieux en mieux compris, leur importance relative reste difficile à quantifier. Traditionnellement, des approches de modèle de données intégrées sont utilisées pour quantifier la réactivité apparente de la MO (c’est-à-dire les constantes de vitesse de dégradation de la MO) sur des sites de forage bien étudiés. Ces approches reposent sur des modèles de réaction-transport (RTM) qui tiennent généralement compte des processus de transport (advection, diffusion moléculaire, bioturbation et bio-irrigation) et de réaction (production, consommation, équilibre), mais leur complexité varie. La réactivité apparente de la MO est généralement considérée comme un paramètre libre qui est utilisé pour ajuster les profils de profondeur, les taux de réaction ou les flux d’échange benthique-pélagique observés. À l’heure actuelle, aucun cadre quantitatif n’existe pour prédire la réactivité apparente de la MO dans les zones où aucun ensemble complet de données benthiques n’est disponible.Pour évaluer l’impact de ce manque de connaissance, nous avons exploré la sensibilité des taux de réaction biogéochimiques benthiques, ainsi que des flux d’échange benthique-pélagique aux variations de la réactivité apparente de la MO (c.-à-d. les paramètres du modèle de con- tinuum réactif a et ν) au moyen d’un modèle diagénétique numérique complexe appliqué aux zones de dépôts sur les plateaux, les talus et en haute mer. Les résultats du modèle montrent que la réactivité apparente de la MO exerce un contrôle dominant sur l’ampleur des taux de réaction biogéochimiques et des flux d’échange benthique-pélagique dans différents environ- nements. L’absence d’un cadre général pour quantifier la réactivité de la MO complique donc la paramétrisation des modèles diagénétiques à l’échelle régionale et mondiale et, ainsi, compromet notre capacité à quantifier le couplage benthique-pélagique global en général et la dynamique de dégradation de la MO en particulier.Pour tendre à meilleure connaissance systématique et quantitative de la réactivité de la MO, la réactivité apparente OM (c.-à-d. les paramètres du modèle de continuum réactif a et ν) est quantifiée par modélisation inverse des profils de sédiments organiques de carbone, de sulfate (et de méthane), ainsi que localisation de la zone de transition sulfate-méthane à l’aide d’un modèle diagénétique numérique complexe pour 14 sites individuels à travers différents environnements de dépôt. Les résultats du modèle mettent à nouveau en évidence le contrôle dominant de la réactivité de l’OM sur les taux de réaction biogéochimiques et les flux d’échanges benthiques. De plus, les résultats montrent que les valeurs déterminées inversement déterminées se situent dans une plage étroite (0,1 <ν<0,2). En revanche, les valeurs déterminées s’étendent sur dix ordres de grandeur (1 ·10−3 <ν< 1·107) et sont donc le principal moteur de la variabilité globale de la réactivité OM. L’exploration de ces tendances dans leur contexte environnemental révèle que la réactivité apparente de l’OM est déterminée par un ensemble dynamique de contrôles environnementaux plutôt que par des contrôles environnementaux uniques traditionnellement proposés (par exemple, la profondeur de l’eau, le taux de sédimentation, les flux OM). Cependant, la forte demande de calcul associée à une telle approche de modèle inverse multi-espèces, ainsi que la disponibilité limitée de données complètes sur l’eau interstitielle, limitent le nombre d’estimations apparentes de la réactivité OM. Par conséquent, tout en fournissant des amorces importantes pour une quantification de la réactivité de l’OM à l’échelle mondiale, les résultats du modèle inverse sont loin de fournir un cadre prédictif.Pour surmonter les limites de calcul et étendre la modélisation inverse de la réactivité apparente de l’OM à l’échelle mondiale, le modèle analytique OMEN-SED est étendu en intégrant une approximation nG du modèle de continuum réactif qui est pleinement cohérente avec la structure générale d’OMEN-SED. La nouvelle version OMEN-SED-RCM fournit ainsi l’efficacité de calcul requise pour la détermination inverse de la réactivité apparente de l’OM (c’est-à-dire les paramètres du modèle de continuum réactif a et ν) à l’échelle mondiale. Les capacités du nouveau modèle OMEN-SED-RCM à capturer les modèles locaux et globaux de dynamique diagénétique observés sont rigoureusement testés par les données du modèle, ainsi que la comparaison modèle- modèle.OMEN-SED-RCM est ensuite utilisé pour déterminer inversement la réactivité apparente de l’OM par modélisation inverse de 394 mesures individuelles du taux d’utilisation de l’oxygène dissous (DOU). Le DOU est couramment utilisé comme indicateur de la réactivité de l’OM, il est plus largement disponible que les ensembles de données exhaustifs sur l’eau interstitielle et les cartes benthiques mondiales/régionales des taux d’utilisation de l’oxygène dissous (DOU) ont été dérivées sur la base de l’ensemble de données DOU croissant. Le test de sensibilité montre que, bien que la modélisation inverse des taux de DOU ne fournisse pas une estimation robuste du paramètre RCM ν, c’est un bon indicateur pour le paramètre RCM a. Sur la base des résultats précédents, le paramètre ν a donc été supposé être globalement constant. Les valeurs a déterminées à l’inverse varient selon l’ordre de grandeur, de a = 0,6 an dans la région polaire sud à a = 5, 6 · 106 dans le Pacifique sud oligotrophique central. Malgré une forte hétérogénéité intra et interrégionale dans la réactivité apparente de la MO benthique, un certain nombre de schémas régionaux clairs qui correspondent largement aux observations précédentes émergent. Des réactivités apparentes élevées de l’OM sont généralement observées dans les régions dominées par des sources marines de MO et caractérisées par un naufrage efficace de l’OM et une dégradation limitée pendant le naufrage. En revanche, les réactivités MO apparentes les plus faibles sont observées pour les régions caractérisées par de faibles taux de production primaire marine, en combinaison avec une grande distance du plateau continental et de la pente, ainsi que des colonnes d’eau profonde. Pourtant, les résultats mettent également en évidence l’importance des processus de transport latéral pour la réactivité apparente de l’OM.En particulier, les sédiments des mers profondes au voisinage d’environnements de marge continentale dynamiques ou sous l’influence de forts courants océaniques peuvent recevoir des apports OM de réactivité comparable provenant d’environnements plus productifs et, ainsi, révéler des réactivités OM plus élevées que ce qui était traditionnellement prévu. Enfin, sur la base du lien fort observé entre la réactivité apparente de l’OM (c’est-à-dire le paramètre RCM a) et le taux DOU, une fonction de transfert qui prédit l’ordre de grandeur du paramètre RCM a en fonction de DOU est utilisée pour dériver, pour nos connaissances, la première carte mondiale de la réactivité apparente de l’OM. Les résultats du modèle des flux et des taux régionaux et mondiaux se situent bien dans la gamme des valeurs observées et également d’accord avec les tendances générales observées au niveau mondial. Les résultats mettent également en évidence le rôle de l’océan profond pour le cycle benthique-pélagique et indiquent une grande variabilité régionale du cycle benthique à grande profondeur. Il s’agit d’une première étape vers une estimation mondiale plus précise du cycle biogéochimique benthique qui tient compte de l’hétérogénéité mondiale du milieu marin. Cet aspect est essentiel pour améliorer notre compréhension des rétroactions benthiques sur le couplage benthique-pélagique et sur le système carbone-climat, qui peuvent ensuite être incorporées aux processus benthiques dans les modèles du système terrestre.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

The Ph.D. thesis deals with one of the most important characteristics of hardened concrete; i.e. the modulus of elasticity. The thesis aims to describe and evaluate the important factors that affect the final value of concrete modulus of elasticity, especially those that can be influenced during construction. Another aim is to find ways to determine the static modulus of elasticity of concrete by non-destructive means (primarily ultrasonic pulse method, resonance method and use of electronic rebound hammers), thus to determine the possibility of creating calibration curve for NDT determination of the modulus of elasticity.

This thesis addresses the issue of cluster dynamics. The theoretical basis is the Porter’s diamond model of industrial clusters and the analysis pursued in the thesis considers the impact of foreign ownership on Porter’s determinants of successful cluster: factor conditions, demand conditions, supported industries and, finally, firms’ strategies and structures. According to Porter, sustainability of clusters is a function of its dynamics and propensity to change, which in turn depends on these four components of the national home base. The analysis is based on a comprehensive set of case studies conducted for the life science industrial cluster located in the Stockholm-Uppsala area. The results indicate that foreign ownership has positive effect on the dynamism of the cluster.

The use of macroeconomic models in the decision-making process avoids costly and sometimes impossible practical experiments. In addition, modeling helps to determine the outcomes of the implementation of various economic programs, the use of certain monetary policy instruments, etc. The search for the new approaches and the use of efficient economic and mathematical tools for adequate reproduction and formalization of dynamic, nonlinear and stochastic interconnections, both between the elements within individual subsystems of the economic system and between its subsystems in general, are constantly in progress.

Beck and Rector (2005) proposed a model of functional outcome in schizophrenia, suggesting the path between neurocognition and functioning is mediated by functional capacity and cognitive processes. These cognitive processes include defeatist performance beliefs, self-stigma and, most recently, metacognition, considered 'thinking about thinking'. Metacognition has been proposed to work in a hierarchy between the object- and meta-level, outlined within Nelson and Narens (1990) model, including several metacognitive components: metacognitive ability, experience and efficiency, connected by metacognitive processes. Firstly, this thesis investigated how different metacognitive components may interact dynamically and predict both what people do in their everyday lives (functional outcome) and how people feel about their everyday lives (subjective recovery outcome) in First Episode Psychosis (N=62), compared to healthy controls (N=73). Following this, this thesis examined the role of metacognition in predicting functional outcome across a three-year period, in FEP (N=26). Finally, it was suggested that metacognition may be expanded to include the way one thinks about oneself through important memories, e.g. self-defining memories (SDMs). The role of SDMs as an additional mediator between neurocognition and functioning in psychosis (N=71) was investigated. Next, using only one of the metacognitive components: metacognitive efficiency, this thesis explored whether this component could be used to explain the presence of anomalous experiences. Anomalous experiences refer to a rich number of various psychic phenomena, including anomalous self-experiences and anomalous perceptual experiences, leading to anomalous delusional beliefs. Initially, this thesis developed and piloted two metacognitive tasks in healthy student sample (N=125). Next, these tasks were used to examine the relationship between anomalous experiences and metacognitive efficiency within the first two samples (N=135): FEP group (N=62) and healthy control (N=73). Current findings demonstrated a role for metacognitive ability in predicting both functional outcome and subjective outcome in FEP, cross-sectionally, and in predicting functional outcome across three years. Alongside this, holding specific self-defining memories was shown to predict functional outcome, independent of neurocognition and metacognition, in FEP. However, no significant association was demonstrated between anomalous experiences and metacognitive efficiency, instead anomalous self-experiences were associated with auditory perceptual biases. This thesis highlights the importance of enhancing metacognitive ability, alongside neurocognitive ability and SDMs, in order to improve functioning.

Epidemiologists rely on human interaction networks for determining states and dynamics of disease propagations in populations. However, such networks are empirical snapshots of the past. It will greatly benefit if human interaction networks are statistically predicted and dynamically created while an epidemic is in progress. We develop an application framework for the generation of human interaction networks and running epidemiological processes utilizing research on human mobility patterns and agent-based modeling. The interaction networks are dynamically constructed by incorporating different types of Random Walks and human rules of engagements. We explore the characteristics of the created network and compare them with the known theoretical and empirical graphs. The dependencies of epidemic dynamics and their outcomes on patterns and parameters of human motion and motives are encountered and presented through this research. This work specifically describes how the types and parameters of random walks define properties of generated graphs. We show that some configurations of the system of agents in random walk can produce network topologies with properties similar to small-world networks. Our goal is to find sets of mobility patterns that lead to empirical-like networks. The possibility of phase transitions in the graphs due to changes in the parameterization of agent walks is the focus of this research as this knowledge can lead to the possibility of disruptions to disease diffusions in populations. This research shall facilitate work of public health researchers to predict the magnitude of an epidemic and estimate resources required for mitigation.

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Fundação de Amparo à Pesquisa do Estado de Minas Gerais
Estudos realizados para avaliar os principais fatores responsáveis pela dinâmica da vegetação na Amazônia tais como clima e/ou desmatamento sugerem a possibilidade da floresta Amazônica não resistir a uma eventual mudança do regime de chuvas, e ser transformada em um ecossistema de vegetação mais esparsa, do tipo savana, o que deu origem ao termo “Savanização da Amazônia”. Parte destes estudos iniciais no entanto utilizavam apenas cenários de climas futuros, negligenciando na maior parte das vezes o efeito do fogo, e principalmente o efeito da limitação nutricional na dinâmica da vegetação. Recentemente, no âmbito da modelagem climática, grandes avanços têm sido realizados na tentativa de se construir modelos que incorporem o efeito da limitação nutricional e do fogo de forma que se possa avaliar e dimensionar os efeitos dos mesmos na vegetação em larga escala. Neste trabalho, o principal objetivo foi avaliar os efeitos isolados e combinados do clima (variabilidade interanual e CO2), fogo (F) e limitação nutricional por fósforo (P) utilizando o modelo de vegetação dinâmica INLAND na transição entre Amazônia-Cerrado. O modelo INLAND é o primeiro modelo brasileiro que permite simular a dinâmica da vegetação incorporando estes fatores. O INLAND caracteriza a vegetação através de tipos funcionais de planta, que combinados de forma diferente dão origem aos biomas. A limitação nutricional no modelo é estabelecida através de uma função linear entre o teor de fósforo total no solo e a capacidade máxima de carboxilação da enzima Rubisco (Vmax). A Rubisco é a principal enzima responsável por regular as taxas de carboxilação nas plantas com mecanismo fotossintético do tipo C3 atuando diretamente na produtividade primária líquida (NPP) e no incremento de biomassa. Dois mapas de Vmáx foram elaborados para serem utilizados como dados de entrada nas simulações, baseados em dados regionais (PR) (medidas de campo) e globais (PG) de teor de P total no solo. No delineamento do experimento numérico, 24 simulações foram realizadas de forma que diferentes combinações entre os fatores clima, P, F e CO2 fossem obtidas. Para validação das simulações, um mapa de índice de área foliar (LAI) MODIS e dados de biomassa foram contrastados com valores simulados pelo modelo INLAND. Os resultados demonstraram que isoladamente, o efeito do fogo sobre a NPP no Cerrado é positivo e maior em relação aos efeitos da limitação nutricional, contrariamente ao que acontece na região Amazônica onde o P atua na diminuição da NPP. O CO 2 por sua vez quando avaliado combinadamente aos efeitos do fogo demonstrou-se como um amenizador, aumentando a NPP na região de transição. Com relação ao clima, o uso de uma variabilidade inter-anual melhorou a representação dos valores de NPP, biomassa e LAI pelo INLAND. Os valores de LAI e biomassa simulados apresentaram boa correlação com os dados observados de forma que o gradiente de vegetação Amazônia - Cerrado conseguiu ser representado. A melhor representação da composição da vegetação pelo modelo INLAND foi quando considerado os efeitos de PG+F+CO2.
Studies to assess the main factors responsible for the dynamics of vegetation in the Amazon such as climate and / or deforestation suggest the possibility of the Amazon rainforest may not resist a potencial change in rainfall patterns, and be converted to an ecosystem of more sparse vegetation like savanna, which gave rise to the term “Amazon Savannization”. Some of these initial studies, however, used only future climate scenarios, neglecting in their majority the fire effects and especially the effect of nutrient limitation on vegetation dynamics. Recently, in the context of climate modeling, advancements have been made in an attempt to build models that incorporate the nutritional restriction effect and the fire to assess and measure their effects on vegetation at a large scale. In this work, the main objective was to evaluate the isolated and combined effects of climate (inter annual variability and CO2), fire (F) and nutritional limitation by phosphorus (P) using the dynamic vegetation model INLAND in the transition between forest-Cerrado. The INLAND model is the first Brazilian model to simulate the vegetation dynamics incorporating these factors. The INLAND characterizes the vegetation through plant functional types, which combined differently give rise to biomes. The nutritional limitation is established through a linear function of the total phosphorus content in the soil and the maximum carboxylation capacity of Rubisco enzyme (Vmax). The Rubisco is the main enzyme responsible for regulating carboxylation rates in plants with the C3 photosynthetic mechanism type acting directly on net primary productivity (NPP) and the increase of biomass. Two regional the datasets of Vmax to be used as input data of the simulations, based on regional (PR) (field measurements) and global data (PG) of total P content in the soil. In the design of numerical experiment, 24 simulations were performed for different combinations of climate factors, P, F and CO2 were obtained. To validate the simulations, regional datasets of dry season leaf area index (LAI), and biomass were compared against simulated values by the INLAND model. The results showed that isolation, the effect of fire on the NPP in the Cerrado is positive and higher than the effects of nutritional restriction, contrary to what happens in the Amazon biome where the P acts to reduce the NPP. The CO2 when evaluated in combination with the effects of fire acted as an attenuator increasing the NPP in the transition region. With respect to the climate, the use of inter-annual variability improved representation of biomass and LAI simulated by INLAND. The LAI and biomass simulated values showed good correlation with Amazon-Cerrado observed gradient. The best representation of the vegetation composition by INLAND was found when the effects of PG+F+CO2 were combined.

Computational models of the flow-induced vibrations of the vocal folds are powerful tools that can be used in conjunction with physical experiments to better understand voice production. This thesis research has been performed to contribute to the understanding of vocal fold dynamics as well as several aspects of computational modeling of the vocal folds. In particular, the effects of supraglottal geometry have been analyzed using a computational model of the vocal folds and laryngeal airway. In addition, three important computational modeling parameters (contact line location, Poisson's ratio, and symmetry assumptions) have been systematically varied to determine their influence on model output. Variations in model response were quantified by comparing glottal width, frequency, flow rate, open quotient, pressures, and wave velocity measures. In addition, the glottal jet was qualitatively analyzed. It was found that for various supraglottal geometries (either symmetrically or asymmetrically positioned), there was little asymmetry of the vocal fold motion despite significant asymmetry in the glottal jet. In addition, the vocal fold motion was most symmetric when consistent jet deflection was present (even if asymmetric). Inconsistent deflection of the glottal jet led to slightly larger asymmetries in vocal fold motion. The contact line location was found to have minimal impact on glottal width, frequency, and flow rate. The largest influence of the contact line location was seen in predicted velocity fields during the closed phase and in the pressure profiles along the vocal fold surfaces. Variations in Poisson's ratio strongly affected vocal fold motion, with lower Poisson's ratios resulting in larger amplitudes. The model did not vibrate when a Poisson's ratio of 0.49999 was used. The response of a full model (with two vocal folds) was shown to vary slightly from that of a half model (one vocal fold and a symmetry boundary condition), the greatest difference being in the deflection and dissipation of the glottal jet. It was concluded that for many scenarios the half model will be sufficient for modeling vocal fold motion; however, a full model is suggested for studies of material asymmetry or glottal jet dynamics. Application of these results to computational models of the vocal folds will lead to improved modeling and understanding of vocal fold dynamics.

Vertical external-cavity surface-emitting lasers are ideal testbeds for studying the influence of the non-equilibrium many-body dynamics on mode locking. As we will show in this thesis, ultra short pulse generation involves a marked departure from Fermi carrier distributions assumed in prior theoretical studies. A quantitative model of the mode locking dynamics is presented, where the semiconductor Bloch equations with Maxwell’s equation are coupled, in order to study the influences of quantum well carrier scattering on mode locking dynamics. This is the first work where the full model is solved without adiabatically eliminating the microscopic polarizations. In many instances we find that higher order correlation contributions (e.g. polarization dephasing, carrier scattering, and screening) can be represented by rate models, with the effective rates extracted at the level of second Born-Markov approximations. In other circumstances, such as continuous wave multi-wavelength lasing, we are forced to fully include these higher correlation terms. In this thesis we identify the key contributors that control mode locking dynamics, the stability of single pulse mode-locking, and the influence of higher order correlation in sustaining multi-wavelength continuous wave operation.

A theoretical explanation of the existence of lipid rafts in cell membranes remains a topic of lively debate. Large, micrometer sized rafts are readily observed in artificial membranes and can be explained using thermodynamic models for phase separation and coarsening. In live cells such domains are not observed and various models are proposed to describe why the systems do not coarsen. We review these attempts critically and show within a phase field approach that membrane bound proteins have the potential to explain the different behaviour observed in vitro and in vivo. Large scale simulations are performed to compute scaling laws and size distribution functions under the influence of membrane bound proteins and to observe a significant slow down of the domain coarsening at longer times and a breakdown of the self-similarity of the size-distribution function
Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich

L’infarctus du myocarde (IDM) est une pathologie décrite comme étant "la mort des cellules myocardiques après une ischémie prolongée". Actuellement, la reperfusion est la stratégie la plus efficace pour limiter l’étendue de cette nécrose myocardique et améliorer le pronostic des patients. Cependant, cette reperfusion entraine des lésions secondaires irréversibles que l’on appelle lésions de reperfusion. Pour protéger le coeur de ces lésions de reperfusion, des stratégies sont à l’étude avec notamment la cardioprotection par le conditionnement ischémique à distance. Ce conditionnement consiste à réaliser de courts épisodes d'ischémie-reperfusion (IR) non délétères au niveau d’un organe distant du coeur. La mitochondrie est un acteur central dans la genèse des lésions de reperfusion mais aussi dans les mécanismes de cardioprotection. Plusieurs études suggèrent que la modulation de la dynamique mitochondriale, regroupant les mécanismes de fission-fusion mitochondriale, pourrait être une nouvelles tratégie thérapeutique pour diminuer les lésions de reperfusion. Dans ce travail nous avons étudié deux modèles de souris transgéniques déficientes soit en protéine de fusion Optic Atrophy 1 (OPA1), soit en protéine de fission Dynamin Related Protein 1 (DRP1). Nous avons montré qu’un déficit partiel en OPA1 était associé à une augmentation des lésions d’IR et à un déséquilibre dans les flux calciques mitochondriaux alors qu’un déficit partiel en DRP1 réduisait les lésions d’IR. Ces données suggèrent qu’une stratégie thérapeutique ciblant la dynamique mitochondriale en faveur d’une fusion pourrait diminuer les lésions d’IR
Myocardial infarction (MI) is defined in pathology as « myocardial cell death due to prolonge dischemia ». Currently, reperfusion is the most effective strategy to limit the extent of this myocardial necrosis and to improve the prognosis of patients. Paradoxically, this reperfusion is the cause of additional irreversible damage, called reperfusion injuries. A strategy that was proven efficient in reducing these injuries is the remote ischemic conditioning (RIC). This strategy consists of applying brief, non invasive, episodes of ischemia reperfusion (IR) to an organ or a tissue distant from the ischemic organ, here the heart. Mitochondria play amajor role in both reperfusion injuries and cardioprotection mechanisms. Several studies suggest that the modulation of mitochondrial dynamics, which is mitochondrial fission and fusion mechanisms, could be a new therapeutic strategy for reducing reperfusion injuries. In this work, we studied two transgenic mouse models, one model is deficient in Optic Atrophy 1(OPA1) fusion protein and the other one is deficient in Dynamin Related Protein 1 (DRP1) fission protein. We showed that a partial OPA1 deficiency was associated with an increase in IR injuries and an imbalance in mitochondrial calcium flux, whereas, a partial DRP1 deficiency decreased IR injuries. These data suggest that a therapeutic strategy modulating the mitochondrial dynamics in favor of fusion could reduce IR injuries

The mean strengths of the wintertime stratospheric polar vortices are known to be related to the phase of the quasi-biennial oscillation (QBO) in the tropical stratosphere from circulation statistics - the "Holton-Tan relationship". The principal topic of this thesis is improving understanding of the mechanism behind the QBO's influence. Following the example of previous studies, the QBO influence on the Northern Hemisphere (NH) extratropics on monthly time scales in an observational reanalysis is examined, and is shown to closely resemble the stratospheric Northern annular mode (NAM). It is argued that this may not be informative about the mechanism, as the response could be NAM-like for many different mechanisms. It is suggested that examining the transient response of the NH extratropics to forcing by the QBO would be much more informative, particularly on time scales of a few days. In a primitive equation model of the middle atmosphere, the long-term stratospheric NH response to imposed zonal torques is often found to be NAM-like under perpetual January conditions, with wave feedbacks making a very important contribution. However, the response in runs with a seasonal cycle is not NAM-like. Investigation of the transient responses indicates the wave feedbacks are qualitatively similar in each case but only strong enough under perpetual January conditions to make the long-term response NAM-like. This supports the hypothesis that feedbacks from large-scale dynamics tend to make the stratospheric response to arbitrary forcings NAM-like, and therefore indicates that the long-term response is not generally useful for understanding forcing mechanisms. Examining the short-term transient response to known torques is found to be more successful at inferring information about the torques than several other previously proposed methods. Finally, the short-term transient response of the NH extratropics to forcing by the easterly QBO phase in a general circulation model is found to be consistent with the proposed mechanism of Holton and Tan (1980), indicating that this mechanism plays a role in the Holton-Tan relationship.

Schools, families, and neighborhoods can support the development of happy, healthy children and adolescents. However, a majority of children in the United States also experience adversity in their early lives that can have deleterious effects on their cognitive and socioemotional development. Measuring and modeling early adversity is fundamental to understanding development as it occurs through interactions with schools, families and neighborhoods. As outlined by Bronfenbrenner's bioecological model of human development, proximal and distal forces shape development, and cannot be isolated when relating measures of the developmental context to outcomes for individuals. For schools and other social programs to support students from high adversity backgrounds, the nature and structure of adversity and contextual influences must be measured and modeled in a robust manner. The three distinct papers in this dissertation describe the construction and evaluation of measurements for adversity, family conflict, neighborhood quality, and school safety, along with models that relate these elements to each other and cognitive outcomes in childhood and adolescence. Structural equation modeling is used to investigate the latent variables generated to measure the constructs and the nature of their relationships. The studies use nationally representative data from the Panel Study of Income Dynamics to create and test the theoretically driven models. The first study constructs and tests latent variables aligned with the Adverse Childhood Experiences (ACEs) framework in order to generate a continuous and theoretically coherent measurement of adversity. The second study uses this ACEs measurement along with measures of family conflict and neighborhood quality to generate and test path models informed by the bioecological theory of development. The third study applies these measures of developmental constructs to the study of safety in schools and identifies the differential function of school safety for children with varying levels of adversity to better understand the potential for school-based interventions. Results from these studies indicate the utility of a latent variable approach to measuring adversity, and the viability of path analysis for the study of how ACEs, family conflict and neighborhood quality influence cognitive outcomes. Additionally, results provide evidence for the necessity of varied and networked developmental supports for children from highly adverse beginnings, above those that may be available through reforms to school safety. Taken together, these studies provide a rich portrait of childhood development incorporating multiple contextual influences, and add to our understanding of what schools can and cannot do to support children.

A theoretical explanation of the existence of lipid rafts in cell membranes remains a topic of lively debate. Large, micrometer sized rafts are readily observed in artificial membranes and can be explained using thermodynamic models for phase separation and coarsening. In live cells such domains are not observed and various models are proposed to describe why the systems do not coarsen. We review these attempts critically and show within a phase field approach that membrane bound proteins have the potential to explain the different behaviour observed in vitro and in vivo. Large scale simulations are performed to compute scaling laws and size distribution functions under the influence of membrane bound proteins and to observe a significant slow down of the domain coarsening at longer times and a breakdown of the self-similarity of the size-distribution function.
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Les éoliennes offshore modernes ont atteint ces dernières années de très grandes dimensions, qui ne cessent d’augmenter en vue de diminuer les coûts de production de l’électricité. Des designs innovants sont alors nécessaires afin d’améliorer les performances aérodynamiques et de réduire les charges structurelles. Les outils de l’état de l’art tels que la théorie de l’élément de pale couplée à la méthode de la quantité de mouvement (BEMT en anglais), utilisés pour la prédiction des charges et performances des rotors, ont été conçus pour des rotors de plus faibles dimensions et dans des conditions standards d’utilisation. Des conditions particulières comme les cas de désalignement du rotor par rapport à l’axe du vent sont a priori hors du domaine de validité des outils de l'état de l'art. Le but de cette thèse est d'étudier des modèles aérodynamiques plus poussés et de les comparer avec les outils de l'état de l'art sur des cas spécifiques. Les écoulements instationnaires sont particulièrement intéressants puisque difficiles à simuler avec les méthodes standards. Ainsi, un code de méthode des panneaux prenant en compte les phénomènes visqueux tels que le décrochage dynamique est comparé à un code BEMT dans des conditions de vent réalistes et avec un fort désalignement du rotor. Les calculs sont réalisés dans le cadre d'un couplage aéro-servo-élastique de manière à être le plus représentatif possible des calculs de chargement effectués dans l'industrie et nécessaires pour la certification des machines. L'impact du modèle de décrochage dynamique est étudié avec les deux méthodes, pour des cas de chargement extrêmes et en fatigue avec désalignement du rotor. Des différences ont été observées entre les deux méthodes et avec plusieurs paramétrisations du modèle de décrochage dynamique. De plus, la prise en compte du couplage servo-élastique modifie les observations faites sur les comparaisons aérodynamiques. De plus, les angles d'attaque observés sur les pales en cas de fort désalignement sont très élevés. L'écoulement autour de profils dans ces conditions est dominé par des effets visqueux non capturés par les méthodes des panneaux ou de BEMT mais modélisés via des modèles semi-empiriques. Des modèles alternatifs doivent donc être utilisés pour mieux prédire de tels phénomènes. Dans la seconde partie de cette thèse l'écoulement autour de profils aérodynamiques d'éoliennes, plus épais que dans l'aéronautique, est étudié à l'aide de Simulation aux Grandes Échelles avec loi de paroi. Plusieurs cas d'écoulement attachés et détachés sont simulés, pour des profils fixes et oscillants. De très grands angles d'attaque sont également simulés, jusqu'à 90°, à un nombre de Reynolds réaliste. Dans les cas attachés et très fortement détachés, la Simulation aux Grandes Échelles avec loi de paroi est capable de capturer correctement l'écoulement avec des maillages peu raffinés. Cependant les cas proches du décrochage se sont révélés plus difficiles à obtenir, et nécessitent des maillages très fins même en utilisant des lois de paroi adéquates. Enfin, des cas oscillants avec fréquence réduite élevée sont également étudiés et comparés avec d'autres modèles. La Simulation aux Grandes Échelles est alors particulièrement adaptée et donne des résultats prometteurs
The size of modern offshore wind turbine rotors has reached very large dimensions and keeps increasing in order to reduce the cost of electricity. More challenging designs are thus needed to improve the aerodynamic performances and reduce the structural loads. The state-of-the-art tools such as Blade Element Momentum Theory (BEMT) used to predict the loads and performances of wind turbines have been designed for much smaller rotors in standard operating conditions. Load cases in specific conditions such as yaw misalignment are a priori out of the validity range for such tools. The goal of the thesis is to investigate more advanced aerodynamic models in order to assess the differences in load predictions compared to state-of-the-art tools. In particular, this work focuses on unsteady flows which represent a challenge for engineering tools. For this purpose, a panel method code including viscous effects such as dynamic stall is compared to a BEMT code in realistic wind conditions with large yaw misalignment. The calculations are performed in the framework of aero-servo-elasto coupling in order to be represen¬tative of the load calculations performed in industry following certification standards. The impact of the dynamic stall model is investigated in particular for both BEMT and panel method, for extreme and fatigue loading in cases of yaw misalignment. Differences have been observed between both codes and for several parametrizations of dynamic stall model. In addition, it has been noticed that including the servo-elasto coupling changes a lot the observations regarding aerodynamic loading. Large angles of at¬tack are observed on wind turbine blades in yaw misalignment cases, and the flow around blade sections in such conditions is particularly affected by viscous effects such as dynamic stall or vortex shedding which are not inherently solved by panel methods nor BEMT but modeled with semi-empirical models. Alternative models such as Large Eddy Simulation (LES) that would capture these effects have to be considered. Wall-modeled LES (WMLES) is thus used in the second part of this thesis to investigate the flow around wind turbine dedicated airfoils, much thicker than airfoils used in aeronautics. Several cases are simulated, for attached and detached flows and in steady or oscillating cases. Angles of attack up to 90° are investigated at realistic Reynolds number. It appears that WMLES is able to capture correctly the main flow features in attached conditions and at very high angle of attack with coarse meshes. However, the near stall cases are more challenging to capture even with appropriate wall laws and require very fine meshes to be correctly solved. A comparison is also performed for motions with high reduced frequency and compared to other models, revealing the promising capacities of WMLES in such cases

Avian influenza is a contagious viral disease caused by influenza virus type A. Avian influenza can be disastrous (if it occurs), due to the short incubation period (about 1--4 days). Thus it is important to study this disease so that we are more prepared to manage it in the future. A classical system of differential equations (the half-saturated incidence model) and three Filippov models --- an avian-only model with culling of infected birds, an SIIR (Susceptible-Infected-Infected-Recovered) model with quarantine of infected humans and an avian-only model with culling both susceptible and infected birds --- that are governed by ordinary differential equations with discontinuous right-hand sides (i.e., differential inclusion) are proposed to study the transmission of avian influenza. The effect of half-saturated incidence is investigated, and the outcome of this model is compared with the bilinear incidence model. Both models remain endemic whenever their respective basic reproduction numbers are greater than one. The half-saturated incidence model generates more infected individuals than the bilinear incidence model. This may be because the bilinear incidence model is underestimating the number of infected individuals at the outbreak. For the Filippov models, the number of infected individuals is used as a reference in applying control strategies. If this number is greater than a threshold value, a control measure has to be employed immediately to avoid a more severe outbreak. Otherwise, no action is necessary. We perform dynamical system analysis for all models. The existence of sliding modes and the flow on the discontinuity surfaces are determined. In addition, numerical simulations are conducted to illustrate the dynamics of the models. Our results suggest that if appropriate tolerance thresholds are chosen such that all trajectories of the Filippov models are converging to an equilibrium point that lies in the region below the infected tolerance threshold or on the discontinuity surface, then no control strategy is necessary as we consider the outbreak is tolerable. Otherwise, we have to apply control strategies to contain the outbreak. Hence a well-defined threshold policy is crucial for us to combat avian influenza effectively.

Influenza A is involved in hundreds of thousands of deaths globally every year resulting from viral infection-related complications. Previous efforts to subdue the virus by preventing proper function of wild-type (WT) neuraminidase (N), and M2 proteins using oseltamivir and amantadine (AMT) or rimantadine (RMT), respectively, exhibited success initially. Over time, these drugs began exhibiting mixed success as the virus developed drug resistance. M2 is a proton channel responsible for the acidification of the viral interior which facilitates release of the viral RNA into the host. M2 has a His37-tetrad that is the selective filter for protons. This protein has been demonstrated to be a feasible target for organic compounds. However, due to a mutation from serine to asparagine at residue 31 of M2, which is found in the majority of influenza strains circulating in humans, AMT and RMT block is insufficient. From simulations, it is unclear whether the insensitivity results from weak binding or incomplete block. The question of how the S31N mutation caused MT and RMT insensitivity in M2 is addressed here by analyzing the binding kinetics of AMT and RMT using the two-electrode voltage clamp electrophysiology method. The dissociation rate constant (k2) is dramatically increased compared to WT for both AMT and RMT, by 1500-fold and 17000-fold respectively. Testing of AMT at 10 mM demonstrates complete block, albeit weak, of the S31N M2 channel. At 10 mM, RMT does not reach complete block even though the binding site is saturated. When RMT is in the bound state, it is not blocking all the current, and is binding without block. These results motivated the development of novel M2 blockers using copper complexes focusing on the His37 complex in M2. I hypothesized that copper complexes would bind with the imidazole of a histidine in the His37 complex and prevent proton conductance. The His37 complex is highly conserved in the M2 channel and, therefore, would be important target for influenza therapeutics. By derivatizing the amines of known M2 blockers, AMT and cyclooctyalmine, to form the iminodiacetate or iminodiacetamide, we have synthesized Cu(II) containing complexes and characterized them by NMR, IR, MS, UV–vis, and inductively coupled plasma mass spectroscopy (ICP-MS). The copper complexes, but not the copper-free ligands, demonstrated H37-specific blocking of M2 channel currents and low micromolar anti-viral efficacies in both Amt-sensitive and Amt-resistant IAV strains with, for the best case, nearly 10-fold less cytotoxicity than CuCl2. Isothermal titration calorimetry was used to obtain enthalpies that showed the copper complexes bind to one imidazole and curve fitting to the electrophysiology data provided rate constants for binding in the M2 channel. Computational chemistry was used to obtain binding geometries and energies of the copper complexes to the His37-tetrad. The results show that the copper complexes do bind with the His37 complex and prevent proton conductance and influenza infection.

Understanding the interactions of predators and their prey and their responses to environmental changes is one of the striking features of ecological research. In this thesis, spring dynamics of phytoplankton and its consumers, zooplankton, were considered in dependence on the environmental conditions in a deep lake (Lake Constance) and a shallow marine water (mesocosms from Kiel Bight), using descriptive statistics, multiple regression models, and process-oriented dynamic simulation models. The development of the spring phytoplankton bloom, representing a dominant feature in the plankton dynamics in temperate and cold oceans and lakes, may depend on temperature, light, and mixing intensity, and the success of over-wintering phyto- and zooplankton. These factors are often correlated in the field. Unexpectedly, irradiance often dominated algal net growth rather than vertical mixing even in deep Lake Constance. Algal net losses from the euphotic layer to larger depth were induced by vertical mixing, but were compensated by the input from larger depth when algae were uniformly distributed over the water column. Dynamics of small, fast-growing algae were well predicted by abiotic variables, such as surface irradiance, vertical mixing intensity, and temperature. A simulation model additionally revealed that even in late winter, grazing may represent an important loss factor of phytoplankton during calm periods when losses due to mixing are small. The importance of losses by mixing and grazing changed rapidly as it depended on the variable mixing intensity. Higher temperature, lower global irradiance and enhanced mixing generated lower algal biomass and primary production in the dynamic simulation model. This suggests that potential consequences of climate change may partly counteract each other. The negative effect of higher temperatures on phytoplankton biomass was due to enhanced temperature-sensitive grazing losses. Comparing the results from deep Lake Constance to those of the shallow mesocosm experiments and simulations, confirmed the strong direct effect of light in contrast to temperature, and the importance of grazing already in early spring as soon as moderate algal biomasses developed. In Lake Constance, ciliates dominated the herbivorous zooplankton in spring. The start of ciliate net growth in spring was closely linked to that of edible algae, chlorophyll a and the vertical mixing intensity but independent of water temperature. The duration of ciliate dominance in spring was largely controlled by the highly variable onset of the phytoplankton bloom, and little by the less variable termination of the ciliate bloom by grazing of meta-zooplankton. During years with an extended spring bloom of algae and ciliates, they coexisted at relatively high biomasses over 15-30 generations, and internally forced species shifts were observed in both communities. Interception feeders alternated with filter feeders, and cryptomonads with non-cryptomonads in their relative importance. These dynamics were not captured by classical 1-predator-1-prey models which consistently predict pronounced predator-prey cycles or equilibria with either the predator or the prey dominating or suppressed. A multi-species predator-prey model with predator species differing in their food selectivity, and prey species in their edibility reproduced the observed patterns. Food-selectivity and edibility were related to the feeding and growth characteristics of the species, which represented ecological trade-offs. For example, the prey species with the highest edibility also had the highest maximum growth rate. Data and model revealed endogenous driven ongoing species alternations, which yielded a higher variability in species-specific biomasses than in total predator and prey biomass. This holds for a broad parameter space as long as the species differ functionally. A more sophisticated model approach enabled the simulation of a continuum of different functional types and adaptability of predator and prey communities to altered environmental conditions, and the maintenance of a rather low model complexity, i.e., low number of equations and free parameters. The community compositions were described by mean functional traits --- prey edibility and predator food-selectivity --- and their variances. The latter represent the functional diversity of the communities and thus, the potential for adaptation. Oscillations in the mean community trait values indicated species shifts. The community traits were related to growth and grazing characteristics representing similar trade-offs as in the multi-species model. The model reproduced the observed patterns, when nonlinear relationships between edibility and capacity, and edibility and food availability for the predator were chosen. A constant minimum amount of variance represented ongoing species invasions and thus, preserved a diversity which allows adaptation on a realistic time-span.
Eine der großen Herausforderungen der heutigen ökologischen Forschung ist es, Veränderungen von Ökosys­temen vorher­zusagen, die mit dem Klimawandel einhergehen. Dafür sind ein umfassendes Verständnis der ver­schiedenen Steuerungsfaktoren des entsprechenden Systems und Kenntnisse zur Anpassungs­fähigkeit des Systems nötig. Auf der Grundlage dieses Wissens, können mit mathemati­schen Modellen Klima­szenarien gerechnet und Vorhersagen erstellt werden. Die vorliegende Arbeit untersuchte die Regulation des Phytoplanktons (kleine freischwebende einzellige Algen) und seiner Konsumenten (Zooplankton, tierische Kleinstlebewesen) sowie deren Wechselspiel während des Frühjahrs mit Bezug auf den Klimawandel. Als Basis dienten langjährige Daten von einem großen tiefen See (Bodensee) sowie Daten von Versuchen mit Organis­men aus einem flachen marinen Ge­wässer (Kieler Förde, Ostsee). Diese Daten wurden mit statistischen Verfahren und mathematischen Modellen ausge­wertet. In Gewässern sind Algen als Primärproduzenten die Nahrungsgrundlage für tieri­sche Organismen bis hin zu Fischen und Meeresfrüchten, und bestimmen die Wasserqualität der Ge­wässer. Daher ist es wichtig zu verstehen, welche Mechanismen die Dynamik der Algen steuern. Der Grundstein für die saisonale Entwicklung von Phyto- und Zooplankton in Gewässern un­serer Breiten wird mit dem Be­ginn des Wachstums im Frühjahr gelegt. Diese Arbeit zeigt, dass es bereits im zeitigen, noch kalten Frühjahr ein Wechselspiel physikalischer und biologischer Steuerungsmechanismen für die Algenent­wicklung gibt. Physikalische Faktoren sind die Wassertemperatur, die Globalstrahlung und die Durchmischung des Gewässers, die durch die Stärke des Windes beeinflusst wird. All diese Steue­rungsmechanismen sind eng miteinander verwoben und werden unterschiedlich stark vom Klimawan­del beeinflusst. Mit mathematischen Modellen gelang es den Einfluss einzelner Faktoren voneinander zu trennen und zu zeigen, dass Effekte durch den Klimawandel sich gegenseitig aufheben oder aber auch verstärken können. Schon geringe Änderungen an der Basis der Nahrungsnetze können weitrei­chende Auswirkungen auf höhere Ebenen habe. Wie stark diese Auswirkungen im Einzelnen sind, hängt entscheidend von der Anpassungsfähigkeit gesamter Ökosysteme und ihrer Artengemeinschaf­ten sowie einzelner Individuen ab. Beispielsweise reagiert die Algengemeinschaft auf einen starken Fraßdruck ihrer Räuber mit einer Verschiebung zu weniger gut fressbaren Algenarten. Diese weniger gut fressbaren Arten unterscheiden sich jedoch auch in anderen Eigenschaften, wie zum Beispiel der Ressourcenausnutzung, von besser fressbaren Algen. In dieser Arbeit wurden Modellansätze entwi­ckelt, die diese Fähigkeit zur Anpassung berücksichtigen. Auf dieser Grundlage und mit Einbeziehung der physikalischen Steuerungsfaktoren können Klimaszenarien gerechnet werden und Vorhersagen für den Einfluss des Klimawandels auf unsere Gewässer gemacht werden, die letztlich auch Perspektiven für Handlungsmöglichkeiten aufzeigen.

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This paper describes the evaluation of the NRL Limited Area Dynamical Weather Prediction Model in simulating coastal atmospheric mesoscale phenomena along the west coast of the United States during the period 0000 UTC 02 May - 1200 UTC 03 May 1990. A graphical comparison technique was used. Model output was compared horizontally with large-scale analyses, station data, cross-section analyses, and vertical profiles at specific locations. The model successfully simulated the wind and temperature fields, but failed to accurately replicate moisture and height fields.

A comprehensive hydrological study of large watersheds in Africa e.g. the Congo basin and the Nile basin has not been vigorously pursued for various reasons. One of the major reasons is the lack of adequate modeling tools that would not be very demanding in terms of input data needs and yet inclusive enough to cover such wide extents (over 3 million square kilometers for the Congo basin). Using a coupled run of the Community Atmospheric model (CAM3) and Community Land Model (CLM3) components of the Community Climate System of Models (CCSM), this study looks into the spatial and temporal variation of precipitation and river runoff in the Congo basin in the light of increasing trends in deforestation of the tropical forests. The effect of deforestation on precipitation and runoff is investigated by changing the land cover-type from the current configuration of broadleaf evergreen/deciduous, non-Artic grass and corn to a mostly grass type of vegetation. Discharge simulation for the river Congo is centered at the point of entrance to the Atlantic Ocean. Although the CLM3 does not presently simulate the observed river runoff to within at least one standard deviation it gives an opportunity to iteratively improve on the land surface parameterization with a possibility of future accurate prediction of mean monthly river runoffs under varying climate scenarios and land use practices. When forced with the National Center for Environment and Prediction (NCEP) re-analysis data the CLM3 runoff simulation results are relatively more stable and much closer to the observed. An improved CLM3 when coupled to CAM3 or other Global Climate Models is definitely a better tool for investigative studies on the regional hydrological cycle in comparison to the traditional methods. There was a slight reduction in rainfall in the first experiment which mimicked a severe form of deforestation and a slight increase in rainfall following low level of deforestation. These changes in rainfall were however statistically insignificant when compared to the control simulation. There was notable heterogeneity in the spatial distribution of the changes in rainfall following deforestation.

Dissertation thesis is focused on rheological properties of asphalt binders and on changes of their performance during the lifetime in road structures. Aging processes of asphalt binders and methods of laboratory aging are described in the theoretical part of the thesis. Furthermore, basic rheological models and related test methods for the evaluation of asphalt binders are described. In the practical part, properties of asphalt binders are investigated after aging process and their performance is evaluated by empirical and functional test methods. The various methods of aging are compared with each other and a relationship between real conditions and laboratory aging is researched. In the next section, vacuum flashed cracked residue (VFCR) is added to the selected asphalt binders and their influence on rheological properties during description of aging of asphalt binders is investigated. The results were used in publication of two certified methodology under the title „The methodology for the evaluation of paving bitumen in terms of susceptibility to thermal oxidative aging“ and „The methodology describes laboratory aging of asphalt mixtures“. The results of the thesis are listed in the conclusion.

We investigate the biological constraints determined by the complex relationships between ecological and immunological processes of host-pathogen interactions, with emphasis on influenza viruses in human, which are responsible for a number of pandemics in the last 150 years. We begin by discussing prolegomenous reviews of historical perspectives on the use of theoretical modelling as a complementary tool in public health and epidemiology, current biological background motivating the objective of the thesis, and derivations of mathematical models of multi-locus-allele systems for infectious diseases with co-circulating serotypes. We provide detailed analysis of the multi-locus-allele model and its age-specific extension. In particular, we establish the necessary conditions for the local asymptotic stability of the steady states and the existence of oscillatory behaviours. For the age-structured model, results on the existence of a mild solution and stability conditions are presented. Numerical studies of various strain spaces show that the dynamic features are preserved. Specifically, we demonstrate that discrete antigenic forms of pathogens can exhibit three distinct dynamic features, where antigenic variants (i) fully self-organize and co-exist with no strain structure (NSS), (ii) sort themselves into discrete strain structure (DSS) with non-overlapping or minimally overlapping clusters under the principle of competitive exclusion, or (iii) exhibit cyclical strain structure (CSS) where dominant antigenic types are cyclically replaced with sharp epidemics dominated by (1) a single strain dominance with irregular emergence and re-emergence of certain pathogenic forms, (2) ordered alternating appearance of a single antigenic type in periodic or quasi-periodic form similar to periodic travelling waves, (3) erratic appearance and disappearance of synchrony between discrete antigenic types, and (4) phase-synchronization with uncorrelated amplitudes. These analyses allow us to gain insight into the age-specific immunological profile in order to untangle the effects of strain structures as captured by the clustering behaviours, and to provide public health implications. The age-structured model can be used to investigate the effect of age-specific targeting for public health purposes.