Texte remanié de: Dissertation--Kulturwissenschaftliche Fakultät--Frankfurt--Europa-Universität Viadrina, 2001.

Thesis (M.A.)--Queen's University at Kingston, 2001. / Includes bibliographical references.

The desired lifetime for CO₂ injection for sequestration is several decades at a high injection rate (up to 10 bbl/min or 2,400 tons/day per injector). Government regulations and geomechanical design constraints may impose a limit on the injection rate such that, for example, the bottomhole pressure remains less than 90% of the hydraulic fracture pressure. Despite injecting below the critical fracture pressure, fractures can nevertheless initiate and propagate due to a thermoelastic stress reduction caused by cool CO₂ encountering hot reservoir rock. Here we develop a numerical model to calculate whether mechanical and thermal equilibrium between the injected CO₂ and the reservoir evolves, such that fracture growth ceases. When such a condition exists, the model predicts the corresponding fracture geometry and time to reach that state. The critical pressure for fracture propagation depends on the thermoelastic stress, a function of rock properties and the temperature difference between the injected fluid and the reservoir (ΔT). Fractures will propagate as long as the thermoelastic stress and the fluid pressure at the fracture tip exceed a threshold; we calculate the extent of a fracture such that the tip pressure falls below the thermoelastically modified fracture propagation pressure. Fracture growth is strongly dependent upon the formation permeability, the level of injection pressure above fracture propagation pressure, and ΔT. / text

Increased levels of carbon dioxide in the atmosphere are now widely attributed as a leading cause for global climate change. As such, research efforts into the capture and sequestration of CO2 from large point sources (flue gas capture) as well as the ambient atmosphere (air capture) are gaining increased popularity and importance. Supported amine materials have emerged as a promising class of materials for these applications. However, more fundamental research is needed before these materials can be used in a practically relevant process. The following areas are considered critical research needs for these materials: (i) process design, (ii) material stability, (iii) kinetics of adsorption and desorption, (iv) improved sorbent adsorption efficiency and (v) understanding the effects of water on sorbent adsorption behavior. The aim of the studies presented in this thesis is to further the scientific community’s understanding of supported amine adsorbents with respect to stability, adsorption efficiency and adsorption behavior with water.

Simulation enables preliminary testing of products that may otherwise be dicult, ex-pensive, or dangerous to test physically. Unfortunately, intellectual property concernscan make it dicult or impossible to share the human-readable simulation models toend-users. In fact, there can even be diculties with sharing executables because ofthe possibility for reverse-engineering. This presents a problem when simulating if themodel relies on components for which the source code or executable is not available,such as proprietary components developed by another party. This thesis investigateswhether it is possible to enable a set of networked peers to all take part in computingthe same simulation without any of them having access to the entire model. One way tosolve this problem is to let each system that holds a model of a component to computeits part of the simulation for a single timestep and to share the new state through peer-to-peer connections with the other systems, once a response has been received fromall other peers, the local simulation can advance one timestep and the process can berepeated. But running a simulation over a network can make it signicantly slower,since local operations on the CPU and memory are much faster than operations overa network, and the peers will be spending most of their time waiting for each other asa result. To avoid such delays, each peer maintains expected values for variables thatare not in the local model, and updates are sent only when a local variable changes.These updates are stamped with the local simulation-time, thus allowing the recipientpeers to know when the update is required in the simulations future, or to when itshould be retroactively applied in the simulations past. Using this technique, the peerscan compute their respective local models under the assumption that the variablesthat the other peers control are unchanged. Thus the peers can advance any numberof timesteps without needing to stop and wait for other peers. These techniques willlikely result in wasted work if one or more peers are advancing their simulation timeslower than the others, when this happens, the peers have the ability to re-distributethe workload on the y by transferring control over models. This also makes it possibleto accommodate for systems joining or leaving the simulation while it is running.In this thesis we show that co-simulating in this fashion is a workable option to tra-ditional simulation when the local models are incomplete, but that the performanceis very dependent on the models being simulated. Especially the relation between thefrequency of required synchronizations, and the time to compute a timestep. In ourexperiments with fairly basic models, the performance ratio, compared to traditionalsimulation, ranged between less than one percent of that of traditional simulation, upto roughly 70%. But with slower models always having a better ratio.

Pioneers are those who, in some way, lead their peers to new destinations. In the evolution of a domain, the pioneers might very well be those who have followed a theoretical principle in some particularly ardent manner, thus leading the rest of the domain toward an evolving research front. The present paper is an attempt to use the tools of domain analysis to diachronically analyze the domain of knowledge organization as it is evolving in North America. That is we use bibliometric tools to identify the axes that define North American knowledge organization and its scientists, who are its pioneers. The evolution of a North American chapter of the International Society for Knowledge Organization (ISKO) marks a growth in coherence of a long active research area. An interesting research question is: what are the characteristics of North American scholarship in knowledge organization? Author co-citation analysis of North American authors whose work appeared in the journal Knowledge Organization is contrasted with author co-citation analysis of authors from outside North America. North American leaders are clearly identified, and some themesâ such as knowledge organization onlineâ that are emergent topics in North America are identified.

Co-operation is one of the main factors which form warm intercommunication, conditioning partnership. Like all social systems, the system of education is based on the co-ordination of actions and on trying to achieve common goals. In the whole educational process the main things are communication and co-operation of the people who organise it. The first condition for cherishing democracy and for optimum education of a child is respect, sincerity and frankness of the staff of a pre-school educational institution. The aim of this paper is to investigate the standpoint on the co-operation of the head and the teachers of a pre-school educational institution and to consider the level of mastering their teleological competence and their psychological and professional readiness to communicate on the whole. The historical evolution of co-operational the opportunities of all the members of the educational process for co-operational, the domination of the theories of management, the microclimate of the institution and the models of behaviour in different institutions are described here. The paper consists of three parts. In the first part the scientific interpretation of co-operation is analysed the following topics: co-operation and communication of the members of educational process, co-operation from the viewpoint of the theory of management, the climate of the educational institution as a body: possible models of educational behaviour and the styles of leadership in a... [to full text]

The influence of regional processes, such as dispersal, on ecological communities has been the focal point of considerable ecological research. Evidence has shown that dispersal can impact community composition through interactions with predation, the introduction of keystone species, and maintenance of species lost due to competitive exclusion. Ecological communities can be characterized by several metrics including species richness, diversity, evenness, abundance and species co-occurrence patterns. Negative species co-occurrence patterns have historically been attributed to competitive interactions between species causing pairs of species to never co-occur. However, little attention has been paid to the contribution of dispersal on species co-occurrence patterns. I have experimentally investigated the influence of dispersal on species co-occurrence patterns in addition to local species richness, total species abundance, evenness, and Simpson’s diversity. Local species richness significantly increased with dispersal, with variation in total local richness being mainly attributed to differences in the rotifer community. Local diversity, total abundance, and evenness were not significantly influenced by changes in the level of dispersal. Species co-occurrence patterns were greatly affected by changes in dispersal, with negative species co-occurrence patterns peaking at intermediate levels of dispersal. The potential for dispersal to increase the number of rare species within a community suggested that the presence of rare species could be behind the changes in the co-occurrence patterns between dispersal treatments. The effect size of the co-occurrence tests increased with the removal of rare species in the intermediate dispersal treatment and decreased in the remaining dispersal treatments. Likely, through mass effects, the presence of rare species, and the establishment of keystone predators changes in the level of dispersal strongly influenced species co-occurrence patterns. I conclude that external processes, like dispersal, can influence species co-occurrence patterns and that caution should be taken when interpreting the mechanisms driving species co-occurrence patterns across landscapes. / Thesis (Master, Biology) -- Queen's University, 2011-09-28 15:00:40.972

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