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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.
281

Image based modeling of complex boundaries

Dillard, Seth Ian 01 May 2011 (has links)
One outstanding challenge to understanding the behaviors of organisms and other complexities found in nature through the use of computational fluid dynamics simulations lies in the ability to accurately model the highly tortuous geometries and motions they generally exhibit. Descriptions must be created in a manner that is amenable to definition within some operative computational domain, while at the same time remaining fidelitous to the essence of what is desired to be understood. Typically models are created using functional approximations, so that complex objects are reduced to mathematically tractable representations. Such reductions can certainly lead to a great deal of insight, revealing trends by assigning parameterized motions and tracking their influence on a virtual surrounding environment. However, simplicity sometimes comes at the expense of fidelity; pared down to such a degree, simplified geometries evolving in prescribed fashions may fail to identify some of the essential physical mechanisms that make studying a system interesting to begin with. In this thesis, and alternative route to modeling complex geometries and behaviors is offered, basing its methodology on the coupling of image analysis and level set treatments. First a semi-Lagrangian method is explored, whereby images are utilized as a means for creating a set of surface points that describe a moving object. Later, points are dispensed with altogether, giving in the end a fully Eulerian representation of complex moving geometries that requires no surface meshing and that translates imaged objects directly to level sets without unnecessary tedium. The final framework outlined here represents a completely novel approach to modeling that combines image denoising, segmentation, optical flow, and morphing with level set- based embedded sharp interface methods to produce models that would be difficult to generate any other way.
282

Modeling time series data with semi-reflective boundaries

Johnson, Amy May 01 December 2013 (has links)
High frequency time series data have become increasingly common. In many settings, such as the medical sciences or economics, these series may additionally display semi-reflective boundaries. These are boundaries, either physically existing, arbitrarily set, or determined based on inherent qualities of the series, which may be exceeded and yet based on probable consequences offer incentives to return to mid-range levels. In a lane control setting, Dawson, Cavanaugh, Zamba, and Rizzo (2010) have previously developed a weighted third-order autoregressive model utilizing flat, linear, and quadratic projections with a signed error term in order to depict key features of driving behavior, where the probability of a negative residual is predicted via logistic regression. In this driving application, the intercept (Λ0) of the logistic regression model describes the central tendency of a particular driver while the slope parameter (Λ1 ) can be intuitively defined as a representation of the propensity of the series to return to mid-range levels. We call this therefore the "re-centering" parameter, though this is a slight misnomer since the logistic model does not describe the position of the series, but rather the probability of a negative residual. In this framework a multi-step estimation algorithm, which we label as the Single-Pass method, was provided. In addition to investigating the statistical properties of the Single-Pass method, several other estimation techniques are investigated. These techniques include an Iterated Grid Search, which utilizes the underlying likelihood model, and four modified versions of the Single-Pass method. These Modified Single-Pass (MSP) techniques utilize respectively unconstrained least squares estimation for the vector of projection coefficients (Β), use unconstrained linear regression with a post-hoc application of the summation constraint, reduce the regression model to include only the flat and linear projections, or implement the Least Absolute Shrinkage and Selection Operator (LASSO). For each of these techniques, mean bias, confidence intervals, and coverage probabilities were calculated which indicated that of the modifications only the first two were promising alternatives. In a driving application, we therefore considered these two modified techniques along with the Single-Pass and Iterative Grid Search. It was found that though each of these methods remains biased with generally lower than ideal coverage probabilities, in a lane control setting they are each able to distinguish between two populations based on disease status. It has also been found that the re-centering parameter, estimated based on data collected in a driving simulator amongst a control population, is significantly correlated with neuropsychological outcomes as well as driving errors performed on-road. Several of these correlations were apparent regardless of the estimation technique, indicating real-world validity of the model across related assessments. Additionally, the Iterated Grid Search produces estimates that are most distinct with generally lower bias and improved coverage with the exception of the estimate of Λ1. However this method also requires potentially large time and memory commitments as compared to the other techniques considered. Thus the optimal estimation scheme is dependent upon the situation. When feasible the Iterated Grid Search appears to be the best overall method currently available. However if time or memory is a limiting factor, or if a reliable estimate of the re-centering parameter with reasonably accurate estimation of the Β vector is desired, the Modified Single-Pass technique utilizing unconstrained linear regression followed by implementation of the summation constraint is a sensible alternative.
283

History of the Forty-Second Parallel as a Political Boundary Between Utah and Idaho

Bergeson, Nancy 01 May 1983 (has links)
The original purpose of this paper was to discover why Cache County, Utah at one time taxed towns now located in the State of Idaho. Later, it became apparent that a history of the forty - second parallel was necessary to fully understand the reasoning used by both the Federal and local governments in setting up the political boundaries of Utah and Cache County. Therefore, it was necessary to research the records of the Federal Government, Cache County Government, the LDS Journal History, and diaries of residents of Cache and Bear Lake Valleys, as well as detailed accounts of Spanish and Mexican negotiations with the United States. I also felt it necessary to obtain copies of maps drawn in the 1800s to appreciate the geographical knowledge available at the time. Boundary decisions in the western United States appeared to be the result of compromise more often than not. The forty - second parallel boundary was originally made to appease two independent nations. Because this spirit of compromise continued in the formation of territories after the United States gained control over both sides of the line and precedent was followed more readily than logic, the boundary did not fully satisfy residents on either side of the border for many years .
284

Application of Biophysical Data to an Unsupervised Classification to Map Ecoregional Boundaries in the Desert Southwest

McClurg, Paxton 01 May 2002 (has links)
An unsupervised classification was applied to continuous biophysical variables in an attempt to delineate ecoregional boundaries in the desert southwest. Output was then compared with ecoregions delineated by the Natural Resources Conservation Service (NRCS), the Environmental Protection Agency (EPA), and the Forest Service at the national level. An attempt was made to use the same biophysical variables for input into the unsupervised classification as was emphasized by the various agencies with their ecoregional classifications at the desert level. Major constraints included data availability at such a large study area, data resolution, and data that were continuous. This eliminated categorical data such as vegetation type, geology type, or soil texture. The aim of the study was to develop a more objective and repeatable approach to identifying self-similar geographic regions.
285

Boundaries for use in wheat variety classification use in Australia

Williams, Richard Malcolm January 2006 (has links)
Suppliers of wheat must ensure that their products have the required quality profile demanded by customers and consistently deliver that quality in order to be competitive. Australia’s wheat industry is highly exposed to such competitive threats because it relies heavily on exports. An integral component in maintaining Australia’s competitiveness has been its classification system. The first step involves the complex process of determining a genotypic quality profile of each variety – a variety classification. At harvest, subsequent steps are the use of a statutory declaration and testing of physical quality traits. Together these steps determine how deliveries of wheat are segregated. A single variety can have different classifications across the 7 classification regions of Australia. Most classification regions are divided along state borders and these are not reflective of potential environmental influences. / The manner in which Australia wheat breeding programs now tackle their task has changed since 1999. The commercially focused companies of the current era have national targets to remain viable, and are focused on costs. Other evolutions associated with the change, are the introduction of different sources of parental material, and moving to more economic composite quality testing regimes instead of the individual site by site testing used in the past. Together, these factors, particularly variety adaptability and stability of performance, have the capacity to increase variability. The likelihood of variation is further increased given that the current classification regions upon which classification decisions are made do not adequately reflect environmental effects on the expression of quality. To determine whether better divisions of the Australian wheat-belt could be identified for variety classification purposes, a substantial spatial and temporal database of historical quality results was assembled. The creation of this relational database was unique, because never before had expansive sets of independent, state-based, quality sub-sets been joined together. However, the data were unbalanced and required alternative statistical tools to be analysed. The relational database was the platform from which three phases of research were conducted. / The first research phase investigated the extent of cross over, or re-ranking of results, statistically referred to as genotype x environment interaction. The approach was to assess balanced data sets, in a manner reminiscent of the most common method identified from the literature. The results of those analyses showed that the size of genotype and environment interaction was small compared with the main effects of genotype and environment. The second phase of research focused on identifying alternative boundaries for classification purposes. Test divisions were compared with the current set of 7 classification regions for the capacity to minimise environmental variance while maintaining differences between the zones of a set. Test divisions were based on fourteen published divisions of the Australian wheat-belt. Analyses were conducting using residual maximum likelihood because of the unbalanced structure of the data. Estimates of variance components, quality trait means and standard errors were calculated. Consideration of such estimates resulted in the identification of 4 different divisions of the wheat-belt that had low environmental variance levels for important quality traits such as maximum resistance, dough development time, and water absorption. / In addition, these 4 divisions of the wheat-belt had fewer number of zones compared with the existing set of classification regions because they linked separate parts of the wheat-belt together. In order of decreasing merit, the 4 divisions of the wheat-belt represented average October maximum temperatures; agro-ecological zones reported by Williams et al. (2002); average annual rainfall; and Departments of Agriculture recommendation zones. A final phase of crosschecking was performed to assess the veracity of the 4 identified divisions. A cluster analysis supported the orientation of their boundaries and it was also observed that the use of fixed boundaries for classification purposes would not be negatively affected by seasonal variation. The 4 divisions of the wheat-belt identified in this research support the use of environmentally focused classification boundaries. In addition to improving the capacity to segregate consistent quality, the linking of geographically separate production areas of the wheat-belt reduced the number of zones and this offers process efficiencies.
286

The smooth + the striated: the home as a locale of cyberspace

Lee, Fang-Ching Unknown Date (has links)
The home is a material place of routine and isolation. Cyberspace, on the other hand, is associated with the lightness of disembodiment and engagement with others in virtual worlds. I am interested in the home as a locale of cyberspace in regard to the relationship between attaching and detaching, territorializing and de-territorializing, the smooth and the striated. My experimentation is about frozen moments in day-to-day situations. Through experiments with light, materials and installations, I intend to draw out a tactile perspective on cyberspace and domesticity. In terms of materials, I am particularly interested in the residues in everyday life. Light and materials are considered to be tactile as well as visual. Performativity, Heuristics and Active Documentation are my main methodological approaches. My work does not seek to fix a solution, but open up an area of ongoing discovery. The physical makings are the ignition for later developments. Once the installation has been set up, the performativity is transferred to the audience. The surrounding space becomes activated because of the energy released by the audience's engagement. Heuristic use of intuition and informal experience was applied in my working process to discover imperceptible traits of materials and daily situations. Active Documentation helps me to re-consider, re-negotiate, reflect and renew my work throughout the project. In this way, hidden codes can be brought out to the surface.
287

Encroachment of sandplain heathland (kwongan) by Allocasuarina huegeliana in the Western Australian wheatbelt: the role of herbivores, fire and other factors

k.maher@murdoch.edu.au, Kellie Maher January 2008 (has links)
Kwongan, also known as sandplain heathland, occurs in remnant vegetation throughout the fragmented landscape of the Western Australian wheatbelt. This vegetation community has high levels of species richness and endemism, and is of high conservation value. In many vegetation remnants in the wheatbelt the native tree species Allocasuarina huegeliana (rock sheoak) is expanding out from its normal range and encroaching into kwongan. A. huegeliana may ultimately dominate the kwongan, causing a decline in floristic diversity. Altered disturbance regimes, particularly the absence of fire and reduced or absent browsing mammal herbivores, are likely to be responsible for causing A. huegeliana encroachment. This study used experimental and observational data from patches of kwongan in three Nature Reserves in the central and southern wheatbelt to investigate the role of fire, native mammal activities and interactions between these two factors in shaping A. huegeliana woodland–kwongan community boundaries. Investigations were carried out into the characteristics of encroaching A. huegeliana populations; the environmental factors affecting the extent of encroachment, naturally recruited juveniles, and seedling emergence and establishment; historical and current abundances of native mammals; and the effects of mammal herbivores on seedling establishment during inter-fire and post-fire periods. Results from this study confirm that A. huegeliana has encroached into kwongan throughout the wheatbelt region and recruitment appears likely to continue in most areas. Few of the environmental factors measured in this study affected the extent of encroachment, the locations of naturally recruited A. huegeliana juveniles, and seedling germination and establishment. Western grey kangaroos (Macropus fuliginosus) browsed extensively on seedlings, which largely prevented them from establishing in open areas of kwongan. However, numerous A. huegeliana seedlings escaped browsing herbivores by establishing in perennial shrubs, where they appeared to be tolerant of increased levels of inter-specific competition. There was no native mammal common to all three Reserves that declined around the time that A. huegeliana encroachment most likely began in the 1970s. In addition, tammar wallabies (Macropus eugenii) had little effect even where their densities were high. It is therefore unlikely that the decline of an individual mammal species initiated encroachment. A. huegeliana encroachment appears to be driven by increased propagule pressure, which is in turn caused by increased inter-fire intervals. Long periods of time without fire have enabled fire-sensitive A. huegeliana trees to produce increasing quantities of seed that are continuously released into kwongan. A range of other factors may interact synergistically with this process to affect encroachment and these are also discussed. This study considered the implications of these findings for management of remnant vegetation in fragmented landscapes, particularly kwongan in the Western Australian wheatbelt, and areas for further research are suggested.
288

Borders, bordering and the limits of democracy rethinking the boundaries of territorial sovereignty /

Whitt, Matt. January 2007 (has links)
Thesis (M. A. in Interdisciplinary Studies: Social and Political Thought)--Vanderbilt University, Dec. 2007. / Title from title screen. Includes bibliographical references.
289

Modernitet i det traditionella : kulturbyggen och gränser inom ett nordsvenskt område

Sjöström, Lars Olov January 2007 (has links)
<p>This doctoral thesis examines how modernisation affects and is affected by existing local culture and identity. It is about the relation between the social and mental barriers experienced, expressed and manifested in the social culture of local community, and modernisation’s dynamic powers over time. The thesis deals with different time periods from the 1800’s until today with regard to expressions and consequences of modernity. People during the societal transformation of Sweden in the 19th and 20th centuries are culturally depicted from a micro-perspective.</p><p>An overall perspective for the analysis of modernity uses the concepts of basal and variable modernity, borrowed from the historian of ideas Sven-Eric Liedman. The perspective makes possible the separation between on the one hand the structural modernisation within the fields of economy, technology and natural sciences, and on the other hand the cultural modernity manifested in conceptions of the world, politics, existential viewpoints, aesthetic expressions and social culture. Within the first-mentioned fields, where basal modernity dominates, a uniform and cumulative developmental pattern emerges as well as an almost self-propelled continuity toward the next innovation or stage of development. Within the latter fields, however, a non-uniform pattern emerges, where modernisation is constantly the object of alternative interpretations and attitudes. This variable modernity is characterised by a cultural struggle between conflicting ideologies and strategies in relation to ongoing modernisation. Different individuals and groups position themselves between acceptance and resistance, progressiveness and the critique of civilisation, the preservation of traditions and the will to change. In this course of events new affinities and identifications, but also new dissociations and antagonisms are created in local social contexts. Modernity leads both to the obliteration of boundaries and to the emergence of new social and mental boundaries. This process can also lead to existing geographical borders being charged with a new ideological content so their importance is revitalised.</p>
290

En Rituell Vardag? : Rumslig strukturering och deponeringsmönster vidjärnåldersbosättningar i centrala Södra England,800-100 BC

Falk, Therese January 2009 (has links)
<p>This paper deals with the question of whether the symbolic language of the late Neolithic and middle Bronze Age was transferred from ceremonial monuments and barrows into the domestic sphere in the late Bronze Age. I will consider such elements as doorway orientation, the significance of boundaries and depositional practices to see if Early-Middle Iron Age settlements were indeed a major scene for ritual behaviour.</p>

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