Yes / This study contributes to the existing literature on the relationship between oil market shocks and the green bond market by investigating the impact of the COVID-19 pandemic on their dynamic correlation. We first decompose the oil market shocks into components using a time-frequency framework. Then, we combine wavelet decomposition and quantile coherence and causality methods to discuss changes during the COVID-19 era. We observe positive effects of both supply-driven and demand-driven oil shocks on the green bond market at most quantile levels. However, supply-driven oil price changes play a major role. The results also indicate that long-term changes have a greater impact than short-term changes on the connection between oil and green bond markets. Nevertheless, the COVID-19 pandemic changed the nature of the causal relationship, as we observed no relationship under extreme market conditions during the pandemic era. We argue that the economic and social impacts of the COVID-19 pandemic have left investors focusing on the short-term substitution between oil and green bond markets. / This research was supported by the Major Projects of the National Natural Science Fund of China [NO. 71991483], the Natural Science Fund of Hunan Province [NO. 2022JJ40647] and the Fundamental Research Funds for the Central Universities of Central South University [NO. 2022ZZTS0353].

Master of Science / Department of Geology / Abdelmoneam Raef / Amid increasing interest in geological sequestration of carbon dioxide (CO2), detailed rock formation characterization has emerged as priority to ensure successful sequestration. Utilizing recent advances in the field of 3D seismic attributes analysis, offers improved opportunities to provide more details when characterizing reservoir formations. In this study, several post-stack seismic attributes integrated with seismic modeling for highlighting critical structural elements and petrophysical facies variation of rock formations at Wellington and Anson-Bates fields, Sumner County, Kansas. A newly acquired 3D Seismic data set and several geophysical well logs are also used to achieve the objectives of this study. Results sought in this study are potentially important for understanding pathways for CO2 to migrate along. Seismic amplitude, coherency, and most negative curvature attributes were used to characterize the subsurface for structural effects on the rock formations of interest. These attributes detect multiple anomaly features that can be interpreted as small throw faults. However, in this study, there is a larger anomalous feature associated with the Mississippian formation that can be interpreted as a small throw fault or incised channel sand. Determining which of the two is very important for flow simulation models to be more exact. Modeling of the seismic was undertaken to help in the interpretation of the Mississippian amplitude anomaly. An artificial neural network, based on well log porosity cross-plots and three seismic attributes, was trained and implemented to yield a seismic petrophysical facies map. The neural network was trained using three volume seismic waveform attributes along with three wells with difference in well log porosity. A reworked lithofacies along small throw faults has been revealed based on comparing the seismic structural attributes and the seismic petrophysical facies. Arbuckle formation characterization was successful to a certain degree. Structural attributes showed multiple faults in the northern half of the survey. These faults are in agreement with known structure in the area associated with the Nemaha uplift. Further characterization of the Arbuckle was hindered by the lack of well data. This study emphasizes the need for greater attention to small-scale features when embarking upon characterization of a reservoir for CO2 based geosequestration.

Made available in DSpace on 2016-04-28T19:34:27Z (GMT). No. of bitstreams: 1 Agnaldo Sergio de Martino.pdf: 3531610 bytes, checksum: 3ef9ead4ca1d82c996c2b9a8895f50cc (MD5) Previous issue date: 2008-06-17 / This essay, oriented to a Text and Speech in Oral and Written Manners approach, studies how the principles of cohesion and coherency may be applied to analysis of text comprehension questions from public concourse examinations, with the purpose of achieving an objective response towards the analyzed question. Cohesion and coherency were already largely discussed by a number of authors, and to each discussion new observation and classification proposals were proposed, related to the principles of cohesion and coherency as well. The essay revises some studies which were written regarding these issues and uses them as base for the development of possible purports for the texts. Having as objective reach to an answer solely to the question proposed in the examination of a public concourse, the several textual marks left by the text producer are observed as to the reader redeems and uses them as support to an objective interpretation of the text / Esta dissertação, na linha de pesquisa Texto e Discurso nas Modalidades Oral e Escrita, estuda como os princípios da coesão e da coerência podem ser aplicados a análises de questões de compreensão de texto das provas de concursos públicos, a fim de se chegar a uma resposta objetiva em relação à questão analisada. A coesão e a coerência já foram muito discutidas por vários autores, e a cada nova discussão surgem novas propostas de observação e classificação dos fatores tanto de coesão quanto de coerência. O trabalho faz uma revisão de alguns estudos que se escreveram a respeito desses assuntos e os utiliza como base para a construção de sentidos possíveis para os textos. Tendo como objetivo chegar a uma resposta apenas para a questão proposta na prova de concurso público, serão observadas as várias marcas textuais deixadas pelo produtor do texto para que o leitor as recupere e as utilize como ponto de apoio para a interpretação objetiva do texto

Dans les analyses d'interaction sol-structure (ISS), la pratique commune en génie civil est de considérer un mouvement uniforme du champ libre à tous les points situés à la surface du sol. Néanmoins, cette considération n'est pas tout à fait réaliste parce que les signaux sismiques sont spatialement différents grâce à l'effet de passage d'ondes, à l'effet de site et aussi aux dispersions et réflexions des ondes qui propagent dans des milieux hétérogènes aléatoires ("incohérence pure"). Ainsi, pour répondre aux problèmes de sécurité des bâtiments et équipements, il est important de faire une analyse d'interaction sol-structure dans la manière plus réaliste. Cela peut être acquis par prendre en compte la variabilité spatiale du champ sismique dans les études d'ISS. Un grand nombre d'études dans la littérature montrent que la prise en compte de la variabilité spatiale du champ sismique dans les études d'ISS peut avoir des effets importants sur la réponse de structures. L'incohérence spatiale du champ sismique due aux dispersions et réflexions des ondes (incohérence pure) peut généralement être modélisée pour ce genre d'études dans le cadre probabiliste par une fonction de cohérence. Le but principal des études réalisées dans cette thèse de doctorat est de construire une description stochastique de la variabilité spatiale du champ sismique par un modèle de cohérence. Ce modèle devrait avoir une relation avec les propriétés physiques et statistiques de milieux considérés. En s'appuyant sur les analyses théoriques de la propagation des ondes sismiques dans des milieux hétérogènes aléatoires, les analyses des données expérimentales obtenues par des enregistrements sur des sites sismiques, ainsi que sur les modélisations numériques de propagation des ondes sismiques dans des milieux hétérogènes aléatoires, un modèle de cohérence est validé dans le cadre des études de cette thèse de doctorat pour représenter la variabilité spatiale du champ sismique dans les études d'interaction sol-structure. L'influence de la variabilité spatiale du champ sismique sur la réponse de structure est également analysée. / In seismic soil-structure interaction studies (SSI), the common practice in Civil Engineering is to consider a uniform movement of free field at any point on the ground surface. However, that assumption is not completely realistic since the seismic ground motions can vary spatially due to wave passage effects, dispersions and reflections of wave propagating in the random heterogeneous media "pure incoherence" and site effects. Therefore, in order to increase the security of buildings and equipment, it is important to do an analysis of seismic soil-structure interactions in the most realistic way. This can be achieved by taking into account the spatial variability of seismic ground motions. Several studies in the literature show that taking into account the spatial variability of seismic ground motions in SSI analyses can have remarkable effects on the structural responses. The spatial incoherence of seismic ground motions due to dispersions and reflections of wave "pure incoherence" can generally be modelled in such analysis by a "coherency function" in frequency domain. The principal goal of this Ph.D thesis is to construct a stochastic description of spatial variability of seismic ground motions by means of coherency functions. Accurately, it aims to propose a parametrical coherency model of spatial variability of seismic ground motions. This later should be related to some physical and statistical properties of the soil at the application sites so that it can be applied in any types of sites. Based on theoretical considerations on coherency of seismic wave propagation in random heterogeneous media, on experimental data analyses, and on numerical modelling of seismic wave propagation in random heterogeneous media, a coherency model is validated and proposed for the analyses of soil-structure interactions. The influence of spatial variability of seismic ground motions on the structural responses are also pointed out by using the validated coherency model.

As técnicas de análise de estabilidade transitória em sistemas elétricos de potência desenvolveram-se significativamente nas últimas duas décadas. Atualmente, o principal desafio dos pesquisadores é a obtenção de técnicas que sejam adequadasa análises em tempo real. Neste sentido, as idéias de Liapunov associadas ao Princípio de Invariância de LaSalle têm sido utilizadas para estimar a bacia de atraçãoo dos sistemas de potência. Embora esta filosofia seja bastante adequada a análises de estabilidade em tempo real, existem alguns obstáculos que impedem a aplicação da mesma à análise de sistemas reais. Dentre estes obstáculos poder-se-ia destacar a impossibilidade de utilização de modelos mais realísticos e a limitação da análise ao primeiro "swing". Em verdade, estes obstáculos estão intimamente relacionados com as limitações do Princípio de Invariância de LaSalle. Para superar estes problemas, propõe-se, neste trabalho, uma extensão deste princípio que é mais geral e portanto mais flexível do que o original. Aproveitando esta maior flexibilidade, duas aplicações em análise de estabilidade transitória são abordadas, ambas com o objetivo de reduzir os obstáculos anteriormente mencionados. Na primeira, propõe-se uma nova função energia para sistemas de potência com perdas nas linhas de transmissão. Mostra-se que esta é uma função de Liapunov no sentido mais geral da extensão do Princípio de Invariância de LaSalle, podendo portanto ser empregada para estudos de estabilidade. Na segunda, uma metodologia de análise de estabilidade multi-"swing" é proposta com base em uma análise de coerência de geradores.

Soil N2O flux is sensitive to soil moisture content and soil temperature, which are in turn sensitive to changes in climate and topography. Thus, N2O flux measurements exhibit a high degree of spatial and temporal variability. Knowing how the spatial distribution of soil N2O flux changes over time in a hummocky, agricultural landscape will identify measurement scales appropriate for estimates of N2O emissions from these types of terrains. As well, little is known about N2O emissions from uncultivated, ephemeral wetlands in agricultural landscapes, but this information is needed for accurate inventories of N2O emissions. The objectives of this study were to describe the spatial and temporal distribution of soil N2O flux in a hummocky agricultural landscape, and to understand how soil water and soil temperature control the spatial and temporal patterns of N2O flux. For a hummocky, agricultural landscape in the Dark Brown soil zone of Saskatchewan, N2O flux and related soil variables were measured along a 128-point transect multiple times over two years and concurrently from a 50 point, stratified design over three years. The spatial and temporal variation in N2O flux followed an event-based / background emission pattern. High flux events were triggered by precipitation events and recession of water from wetlands following spring snowmelt. Days with high mean flux were characterized by highly skewed (reverse J-shaped) distributions. High variance and coherency was observed at cultivated wetland elements during emission events. Strong location-dependent positive relationships were found between soil N2O flux and water-filled pore space or soil temperature, related to specific landscape elements. Background emissions were characterized by random variation or cyclic behavior that ranged in scale from 20 to 60 m. Cumulative emissions were highest from cultivated wetlands and basin centers of uncultivated wetlands, although emissions from cultivated wetlands were much more important to total cumulative emissions on an area basis. The results indicate that models intended to estimate N2O flux from these landscapes cannot rely on a single predictive relationship, but will have to incorporate predictive relationships localized at specific landscape elements depending on the time of year. At certain times predictive relationships cannot be used and up-scaled estimates will have to rely on direct measurement of emissions.

En esta tesis hemos identificado tres de los mayores cuellos de botella para el rendimiento y escalabilidad de las arquitecturas many-core CMP de memoria compartida. En particular, los mecanismos de sincronización de barrera y cerrojo cuando presentan alta contención, así como los protocolos hardware de coherencia de caché en el mantenimiento de la coherencia del uso de bloques memoria compartidos en una jerarquía de memoria. Para paliar estas deficiencias y aprovechar más el rendimiento de estas arquitecturas, hemos propuesto tres mecanismos hardware: GBarrier, para un mecanismo de barreras eficiente; GLock, para un manejo justo y eficiente de la contención en el acceso a las secciones críticas protegidas por cerrojos; y ECONO, un protocolo de coherencia muy simple que aporta gran eficiencia a bajo costo. La tesis concluye que nuestras propuestas resuelven de manera eficiente los problemas de rendimiento derivados de implementaciones ineficientes para sincronización y coherencia en arquitecturas many-core CMP. / In this thesis we have identified three of the major problems that restrict efficiency and scalability in future shared-memory tiled many-core CMPs. In particular, the synchronization operations of barriers and locks under highly-contended scenarios, and the hardware-based cache coherence protocols when dealing with the maintenance of coherence of all memory blocks across all levels of a memory hierarchy. To alleviate such performance bottlenecks in order to harness the computational power of such systems, we have proposed three hardware-based mechanisms: GBarrier, a very efficient barrier mechanism; GLock, an efficient and fair mechanism to implement highly-contended locks; and ECONO, a simple and efficient hardware coherence protocol. In light of our performance results obtained in this thesis, we can affirm that our proposals represent a step forward towards the resolution of the challenges that many-core CMP architectures will pose to computer architects.

Soil N2O flux is sensitive to soil moisture content and soil temperature, which are in turn sensitive to changes in climate and topography. Thus, N2O flux measurements exhibit a high degree of spatial and temporal variability. Knowing how the spatial distribution of soil N2O flux changes over time in a hummocky, agricultural landscape will identify measurement scales appropriate for estimates of N2O emissions from these types of terrains. As well, little is known about N2O emissions from uncultivated, ephemeral wetlands in agricultural landscapes, but this information is needed for accurate inventories of N2O emissions. The objectives of this study were to describe the spatial and temporal distribution of soil N2O flux in a hummocky agricultural landscape, and to understand how soil water and soil temperature control the spatial and temporal patterns of N2O flux. For a hummocky, agricultural landscape in the Dark Brown soil zone of Saskatchewan, N2O flux and related soil variables were measured along a 128-point transect multiple times over two years and concurrently from a 50 point, stratified design over three years. The spatial and temporal variation in N2O flux followed an event-based / background emission pattern. High flux events were triggered by precipitation events and recession of water from wetlands following spring snowmelt. Days with high mean flux were characterized by highly skewed (reverse J-shaped) distributions. High variance and coherency was observed at cultivated wetland elements during emission events. Strong location-dependent positive relationships were found between soil N2O flux and water-filled pore space or soil temperature, related to specific landscape elements. Background emissions were characterized by random variation or cyclic behavior that ranged in scale from 20 to 60 m. Cumulative emissions were highest from cultivated wetlands and basin centers of uncultivated wetlands, although emissions from cultivated wetlands were much more important to total cumulative emissions on an area basis. The results indicate that models intended to estimate N2O flux from these landscapes cannot rely on a single predictive relationship, but will have to incorporate predictive relationships localized at specific landscape elements depending on the time of year. At certain times predictive relationships cannot be used and up-scaled estimates will have to rely on direct measurement of emissions.

The presence of fractures, joints and karst features within rock strongly influence the hydraulic and mechanical behavior of a rock mass, and there is a strong desire to characterize these features in a noninvasive manner, such as by using ground penetrating radar (GPR). These features can alter the incident waveform and polarization of the GPR signal depending on the aperture, fill and orientation of the features. The GPR methods developed here focus on changes in waveform, polarization or texture that can improve the detection and discrimination of these features within rock bodies. These new methods are utilized to better understand the interaction of an invasive shrub, Juniperus ashei, with subsurface flow conduits at an ecohydrologic experimentation plot situated on the limestone of the Edwards Aquifer, central Texas. First, a coherency algorithm is developed for polarimetric GPR that uses the largest eigenvalue of a scattering matrix in the calculation of coherence. This coherency is sensitive to waveshape and unbiased by the polarization of the GPR antennas, and it shows improvement over scalar coherency in detection of possible conduits in the plot data. Second, a method is described for full-waveform inversion of transmission data to quantitatively determine fracture aperture and electromagnetic properties of the fill, based on a thin-layer model. This inversion method is validated on synthetic data, and the results from field data at the experimentation plot show consistency with the reflection data. Finally, growing hierarchical self-organizing maps (GHSOM) are applied to the GPR data to discover new patterns indicative of subsurface features, without representative examples. The GHSOMs are able to distinguish patterns indicating soil filled cavities within the limestone. Using these methods, locations of soil filled cavities and the dominant flow conduits were indentified. This information helps to reconcile previous hydrologic experiments conducted at the site. Additionally, the GPR and hydrologic experiments suggests that Juniperus ashei significantly impacts infiltration by redirecting flow towards its roots occupying conduits and soil bodies within the rock. This research demonstrates that GPR provides a noninvasive tool that can improve future subsurface experimentation.

As técnicas de análise de estabilidade transitória em sistemas elétricos de potência desenvolveram-se significativamente nas últimas duas décadas. Atualmente, o principal desafio dos pesquisadores é a obtenção de técnicas que sejam adequadasa análises em tempo real. Neste sentido, as idéias de Liapunov associadas ao Princípio de Invariância de LaSalle têm sido utilizadas para estimar a bacia de atraçãoo dos sistemas de potência. Embora esta filosofia seja bastante adequada a análises de estabilidade em tempo real, existem alguns obstáculos que impedem a aplicação da mesma à análise de sistemas reais. Dentre estes obstáculos poder-se-ia destacar a impossibilidade de utilização de modelos mais realísticos e a limitação da análise ao primeiro "swing". Em verdade, estes obstáculos estão intimamente relacionados com as limitações do Princípio de Invariância de LaSalle. Para superar estes problemas, propõe-se, neste trabalho, uma extensão deste princípio que é mais geral e portanto mais flexível do que o original. Aproveitando esta maior flexibilidade, duas aplicações em análise de estabilidade transitória são abordadas, ambas com o objetivo de reduzir os obstáculos anteriormente mencionados. Na primeira, propõe-se uma nova função energia para sistemas de potência com perdas nas linhas de transmissão. Mostra-se que esta é uma função de Liapunov no sentido mais geral da extensão do Princípio de Invariância de LaSalle, podendo portanto ser empregada para estudos de estabilidade. Na segunda, uma metodologia de análise de estabilidade multi-"swing" é proposta com base em uma análise de coerência de geradores.