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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

Multiscale Spectral-Domain Parameterization for History Matching in Structured and Unstructured Grid Geometries

Bhark, Eric Whittet 2011 August 1900 (has links)
Reservoir model calibration to production data, also known as history matching, is an essential tool for the prediction of fluid displacement patterns and related decisions concerning reservoir management and field development. The history matching of high resolution geologic models is, however, known to define an ill-posed inverse problem such that the solution of geologic heterogeneity is always non-unique and potentially unstable. A common approach to improving ill-posedness is to parameterize the estimable geologic model components, imposing a type of regularization that exploits geologic continuity by explicitly or implicitly grouping similar properties while retaining at least the minimum heterogeneity resolution required to reproduce the data. This dissertation develops novel methods of model parameterization within the class of techniques based on a linear transformation. Three principal research contributions are made in this dissertation. First is the development of an adaptive multiscale history matching formulation in the frequency domain using the discrete cosine parameterization. Geologic model calibration is performed by its sequential refinement to a spatial scale sufficient to match the data. The approach enables improvement in solution non-uniqueness and stability, and further balances model and data resolution as determined by a parameter identifiability metric. Second, a model-independent parameterization based on grid connectivity information is developed as a generalization of the cosine parameterization for applicability to generic grid geometries. The parameterization relates the spatial reservoir parameters to the modal shapes or harmonics of the grid on which they are defined, merging with a Fourier analysis in special cases (i.e., for rectangular grid cells of constant dimensions), and enabling a multiscale calibration of the reservoir model in the spectral domain. Third, a model-dependent parameterization is developed to combine grid connectivity with prior geologic information within a spectral domain representation. The resulting parameterization is capable of reducing geologic models while imposing prior heterogeneity on the calibrated model using the adaptive multiscale workflow. In addition to methodological developments of the parameterization methods, an important consideration in this dissertation is their applicability to field scale reservoir models with varying levels of prior geologic complexity on par with current industry standards.
32

Efficient algorithms for bipartite matching problems with preferences

Sng, Colin. January 2008 (has links)
Thesis (Ph.D.) - University of Glasgow, 2008. / Ph.D. thesis submitted to the Department of Computing Science, Faculty of Information and Mathematical Sciences, University of Glasgow, 2008. Includes bibliographical references. Print version also available.
33

Essays on contracts and social preferences /

Zubrickas, Robertas, January 2009 (has links)
Diss. Stockholm : Handelshögskolan, 2009.
34

Finding optimal solutions for covering and matching problems

Moser, Hannes January 2009 (has links)
Zugl.: Jena, Univ., Diss., 2009
35

Connectionist models of stereo vision

Stewart, Charles V. January 1900 (has links)
Thesis (Ph. D.)--University of Wisconsin--Madison, 1988. / Typescript. Vita. Description based on print version record. Includes bibliographical references (p. 216-221).
36

Automatic gait recognition via statistical approaches

Huang, Ping Sheng January 1999 (has links)
No description available.
37

Extending functional databases for use in text-intensive applications

Sheldrake, Simon N. January 2002 (has links)
This thesis continues research exploring the benefits of using functional databases based around the functional data model for advanced database applications-particularly those supporting investigative systems. This is a growing generic application domain covering areas such as criminal and military intelligence, which are characterised by significant data complexity, large data sets and the need for high performance, interactive use. An experimental functional database language was developed to provide the requisite semantic richness. However, heavy use in a practical context has shown that language extensions and implementation improvements are required-especially in the crucial areas of string matching and graph traversal. In addition, an implementation on multiprocessor, parallel architectures is essential to meet the performance needs arising from existing and projected database sizes in the chosen application area.
38

On interaction and efficiency : prematch investments with hidden characteristics

Bidner, Christopher 05 1900 (has links)
I develop three models that are designed to aid in the analysis of environments in which agents i) benefit from interacting with others, and ii) optimally choose their characteristics mindful of the fact that such choices will influence the quality of interaction that they can expect. Of central interest is the ways in which a concern for interaction affects the efficiency with which agents choose their characteristics. The first two models contrast with previous work in that each agents' relevant characteristics are both unobserved and endogenously determined. The first model provides an explanation for credentialism in the labour market, and demonstrates how a concern for interaction can lead to over-investment in the relevant characteristic. The second model is motivated by human capital development in the presence of peer effects, and demonstrates how a concern for interaction can exacerbate an inherent under-investment problem. The third model retains the feature of unobserved characteristics, and contrasts with previous work by embedding frictions in the process by which agents compete for partners. The model is set in a labour market and demonstrates that outcomes of interest (equilibrium matching patterns, income, inequality and welfare) are generally not monotonic in the level of frictions. / Arts, Faculty of / Vancouver School of Economics / Graduate
39

Three Essays in Microeconomics:

Kumar, Navin January 2021 (has links)
Thesis advisor: Arthur Lewbel / In this series of essays, I apply the tools of economics to a variety of real world problems. The first essay looks at the impact of a gun control regulation on mortality and crime. A third of US states have removed all restrictions on carrying concealed handguns. This might decrease crime by invisibly arming law-abiding citizens, or increase it by eliminating penalties for criminals. It could have no effect at all, because handguns are easily hidden, so anyone who wished to carry a gun was already doing so. I compare counties along the borders of states that liberalized concealed carry to contiguous counties in neighboring states that did not, using mortality and crime micro-data. I find that deregulation had no impact on homicide, violent crime, firearm mortality, firearm usage, or firearm ownership. The second essay, co-authored with Sajala Pandey, looks at the impact of an earthquake in Nepal on child development. Biologists have posited that prenatal maternal stress (PNMS) has an adverse impact on child development, possibly via the process of epigenetic imprinting which occurs during the first trimester. Researchers have attempted to study this link by using natural disasters as a source of exogenous variation. A shortcoming of these studies is that natural disasters may also affect prenatal healthcare provision, either by decreasing it’s provision (due to infrastructure being destroyed) or increasing it (thanks to aid flowing into the region.) We look at the impact of 2015 Earthquake in Nepal on children who were (a) in utero at the time of the earthquake and (b) in areas severely affected by it. Consistent with theories from PNMS, we find that the earthquake adversely impacted their height-for-age, and the effects were concentrated on individuals who were in the first trimester of gestation. These negative effects were entirely offset by an increase in the consumption of antenatal healthcare. We find that the earthquake resulted in a improvement in development indicators for those children who were in severely affected areas but not in-utero at the time of the earthquake, highlighting the importance of healthcare provision in early childhood. The third essay, co-authored with Andrew Copland, proposes a solution to the problem of assigning multiple scarce goods to agents in the absence of prices, for example assigning seats in courses to students in a university. Students submit a list of preferences over courses, a lottery for rankings is held, and an algorithm allocates each student their top available course, reversing their ranks at the end of each round. Then, for each student, the algorithm compares their outcomes to the outcomes generated by every alternative ordering they could have set. Whenever such revisions result in more preferred outcomes, their preferences are replaced with the alternative. Our solution is non-dictatorial and Pareto optimal. When it converges without encountering a loop, it is strategy-proof. It retains properties even in small economies. We compare our algorithm to alternatives. / Thesis (PhD) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Economics.
40

Schema and Ontology Matching with COMA++

Aumüller, David, Do, Hong-Hai, Massmann, Sabine, Rahm, Erhard 05 November 2018 (has links)
We demonstrate the schema and ontology matching tool COMA++. It extends our previous prototype COMA utilizing a composite approach to combine different match algorithms [3]. COMA++ implements significant improvements and offers a comprehensive infrastructure to solve large real-world match problems. It comes with a graphical interface enabling a variety of user interactions. Using a generic data representation, COMA++ uniformly supports schemas and ontologies, e.g. the powerful standard languages W3C XML Schema and OWL. COMA++ includes new approaches for ontology matching, in particular the utilization of shared taxonomies. Furthermore, different match strategies can be applied including various forms of reusing previously determined match results and a so-called fragmentbased match approach which decomposes a large match problem into smaller problems. Finally, COMA++ cannot only be used to solve match problems but also to comparatively evaluate the effectiveness of different match algorithms and strategies.

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