• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 265
  • 122
  • 22
  • 8
  • 8
  • 8
  • 8
  • 8
  • 8
  • 6
  • 3
  • 1
  • 1
  • Tagged with
  • 545
  • 104
  • 53
  • 53
  • 52
  • 52
  • 46
  • 44
  • 40
  • 40
  • 39
  • 38
  • 36
  • 33
  • 33
  • 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.
431

Implications of GRACE Satellite Gravity Measurements for Diverse Hydrological Applications

Yirdaw-Zeleke, Sitotaw 09 April 2010 (has links)
Soil moisture plays a major role in the hydrologic water balance and is the basis for most hydrological models. It influences the partitioning of energy and moisture inputs at the land surface. Because of its importance, it has been used as a key variable for many hydrological studies such as flood forecasting, drought studies and the determination of groundwater recharge. Therefore, spatially distributed soil moisture with reasonable temporal resolution is considered a valuable source of information for hydrological model parameterization and validation. Unfortunately, soil moisture is difficult to measure and remains essentially unmeasured over spatial and temporal scales needed for a number of hydrological model applications. In 2002, the Gravity Recovery And Climate Experiment (GRACE) satellite platform was launched to measure, among other things, the gravitational field of the earth. Over its life span, these orbiting satellites have produced time series of mass changes of the earth-atmosphere system. The subsequent outcome of this, after integration over a number of years, is a time series of highly refined images of the earth's mass distribution. In addition to quantifying the static distribution of mass, the month-to-month variation in the earth's gravitational field are indicative of the integrated value of the subsurface total water storage for specific catchments. Utilization of these natural changes in the earth's gravitational field entails the transformation of the derived GRACE geopotential spherical harmonic coefficients into spatially varying time series estimates of total water storage. These remotely sensed basin total water storage estimates can be routinely validated against independent estimates of total water storage from an atmospheric-based water balance approach or from well calibrated macroscale hydrologic models. The hydrological relevance and implications of remotely estimated GRACE total water storage over poorly gauged, wetland-dominated watershed as well as over a deltaic region underlain by a thick sand aquifer in Western Canada are the focus of this thesis. The domain of the first case study was the Mackenzie River Basin wherein the GRACE total water storage estimates were successfully inter-compared and validated with the atmospheric based water balance. These were then used to assess the WATCLASS hydrological model estimates of total water storage. The outcome of this inter-comparison revealed the potential application of the GRACE-based approach for the closure of the hydrological water balance of the Mackenzie River Basin as well as a dependable source of data for the calibration of traditional hydrological models. The Mackenzie River Basin result led to a second case study where the GRACE-based total water storage was validated using storage estimated from the atmospheric-based water balance P-E computations in conjunction with the measured streamflow records for the Saskatchewan River Basin at its Grand Rapids outlet in Manitoba. The fallout from this comparison was then applied to the characterization of the Prairie-wide 2002/2003 drought enabling the development of a new drought index now known as the Total Storage Deficit Index (TSDI). This study demonstrated the potential application of the GRACE-based technique as a tool for drought characterization in the Canadian Prairies. Finally, the hydroinformatic approach based on the artificial neural network (ANN) enabled the downscaling of the groundwater component from the total water storage estimate from the remote sensing satellite, GRACE. This was subsequently explored as an alternate source of calibration and validation for a hydrological modeling application over the Assiniboine Delta Aquifer in Manitoba. Interestingly, a high correlation exists between the simulated groundwater storage from the coupled hydrological model, CLM-PF and the downscaled groundwater time series storage from the remote sensing satellite GRACE over this 4,000 km2 deltaic basin in Canada.
432

Network evolution: the origins, development and effectiveness of Manitoba's railway system

McCombe, Christopher G. L. 13 September 2011 (has links)
This thesis examines the characteristics of railway infrastructure development and associated issues in Manitoba, Canada. The period under consideration dates from when the first tracks were laid in 1878 through to the completion of the Hudson Bay Railway in 1929. Setting the scene is a template for railway development in general, one that allows hypotheses to be drawn that are specific to Manitoba. In order to test those hypotheses it is necessary to first provide a comprehensive overview of the historical evolution of the railway network. Next, aspects of graph theory are reviewed, identifying the methodology most appropriate for a spatial analysis of railway networks. This analysis attempts to draw conclusions about the relationship between the railway companies and the governments, people and geography that they were compelled to deal with. The testing of these forms revealed that while the Manitoba railway network is very complex, it never arrived at the maximum possible complexity.
433

Go west: urbanism, mobility, and ingenuity in western Canadian writing and everyday practice

Romanik, Barbara 16 April 2015 (has links)
In early criticism of Western Canadian literature, prairie spaces were constructed as predominantly rural in order to set the region and prairie writing apart from the rest of Canada and other Canadian literature. In time, prairie criticism’s focus on rural realist texts led to the marginalization of urban prairie writing and the construction of urban spaces as corrupt and artificial in comparison to the natural and virtuous rural environment. I work to remedy the absence of urban texts in the criticism of prairie literature, and I argue that prairie cities are dynamic and mobile worlds where prairie inhabitants exercise their agency through everyday practices. Utilizing the work of Raymond Williams, I show how urban and rural spaces are constructed in the canonical prairie texts of Grove, Ostenso, and Stead to serve various capitalist interests and colonial ideologies. I explore the depiction of Winnipeg in Durkin’s The Magpie as a dynamic, complex, and politically engaged space. Moreover, I use Michel de Certeau’s work to assert that the underprivileged and colonized individuals in the city subvert and utilize the systems and organizations of those in power. They develop an increased deviousness and take advantage of incidental and multifarious opportunities that come their way as they work, dwell, and move about in everyday life. Subsequently, I look at urban writing by women, Eastern-European immigrants, and Aboriginal writers and show that they use urban spaces, everyday practices, and writing to exercise their agency. To destabilize unitary forces in language, to depict their own experiences, and to convey their own meanings of home, labour, and community, marginalized writers employ wordplay, humour, historical and cultural references, and intertextuality. I also use Jane M. Jacobs’ work on postcolonial cities and Tim Cresswell’s theories of mobility. I read prairie cities as places of competing mobilities and networks of dominances and resistances, where colonized individuals negotiate complex, hybrid, and authentic identities. The urban prairie texts I explore demonstrate the possibility of political, social, and economic changes, and a beneficial relationship with the prairie environment.
434

Modélisation des impacts du changement climatique sur les écosystèmes prairiaux. Voies d'adaptation des systèmes fourrragers

Graux, Anne-Isabelle 26 January 2011 (has links) (PDF)
Les prairies assurent différents services auprès de l'agriculture et de la société, dont les plus fondamentaux sont de produire le lait et la viande que nous consommons, mais également d'atténuer les émissions de gaz à effet de serre (GES) en piégeant une partie du carbone atmosphérique dans leurs sols. L'anticipation des risques associés à la continuité de ces services, dans le contexte de changement climatique (CC) et démographique futur, est l'un des enjeux agricole et sociétal de demain. Dans ce cadre, cette thèse vise à i) modéliser les impacts du CC sur les services et le bilan de GES des prairies, en tenant compte de la variabilité climatique accrue prédite par les modèles climatiques, mais également ii) à fournir des pistes d'adaptations du système fourrager dans le cas de systèmes d'élevage bovin herbagers. Pour cela, nous avons développé les modules animal et végétal de PaSim afin, d'une part, de représenter de façon mécaniste les performances animales et les émissions de méthane entérique au pâturage et, d'autre part, de rendre compte des interactions de la diversité végétale avec le CC et la gestion des prairies. PaSim a ensuite été utilisé pour simuler, en 12 sites français, les impacts du CC sur des prairies mono ou plurispécifiques, dans différentes conditions pédoclimatiques et de gestion. Le modèle a été forcé par des scénarios climatiques à haute résolution couvrant la période 1950-2100 et issus de différents scénarios socio-économiques, modèles climatiques et méthodes de régionalisation / initialisation. Les conséquences du CC sont globalement assez favorables, hormis pour la production fourragère estivale et la restitution d'eaux aux nappes, pour lesquels les risques d'une diminution significative sont accrus. Les sites plus arides ne sont pas nécessairement ceux qui connaîtront la plus forte évolution négative, même si, en absolu, ils restent ceux présentant les déficits fourragers et hydriques les plus forts. De nouvelles opportunités pour la production fourragère s'offre aux saisons autres que l'été, laissant présager de changements saisonniers importants qui nécessiteront fatalement une adaptation des systèmes d'élevage de ruminants. Une étude de cas, centrée sur les bassins de production breton et du Massif Central, a permis de montrer que ces changements pourraient s'accompagner de modifications de la distribution de fourrages et de concentré en complément de l'herbe pâturée, avec parfois, une exclusion des troupeaux de la pâture l'été. Des systèmes fourragers offrant une certaine flexibilité face à l'aléa climatique pourraient permettre d'exploiter à son maximum l'herbe pâturée, avec des temps de pâturage plus longs et davantage de surfaces allouées au pâturage, et par conséquent des chargements plus élevés. Ces adaptations ne devraient pas nuire au bilan net de GES à l'échelle du système, exprimé par UGB jour. En revanche, afin de soutenir le potentiel de production, elles pourraient nécessiter un recours plus important à l'azote et, de fait, augmenter les pollutions azotées à l'échelle du système.
435

Designing a vegetative cover on landfill and hazardous waste multi-layer cap systems

Hill, Dean January 1996 (has links)
Current Indiana regulations regarding vegetative covers on multi-layer cap systems recommend a standard seeded turf as defined by the Indiana Department of Transportation. Although in its infancy, the use of native prairie grasses and forbs is beginning to generate interest as a viable vegetative cover. This creative project examines past influences that dictated the selection of vegetative covers, examines the use of native prairie grasses and forbs, and creates and applies a design "model" for an existing hazardous waste site located in Albany, Indiana.The goals of this creative project are to identify standard design guidelines for vegetative covers on hazardous waste and landfill multi-layer cap systems, evaluate standard guidelines and case studies of hazardous waste site vegetative covers, recommend changes to standard design guidelines, recommend an alternative vegetative cover using native prairie plants, apply new design guidelines to an existing hazardous waste site (Muncie Racetrack Site) using the alternative cover, and evaluate the results of the guidelines with the alternative cover. / Department of Landscape Architecture
436

Assessment of small scale tallgrass prairie restoration in an urban environment

Mutch, Paul D. 26 October 2007 (has links)
Tallgrass prairie restoration is an important conservation activity in rural areas. However, little is known about prairie restoration in urban environments. The overall objective of this study was to characterize and better understand urban prairie restoration. This was carried out through an examination of 29 restoration sites within Winnipeg, Manitoba. The results indicated that actively restored urban prairies were successful and high in diversity. Multiple attributes of the restorations were examined as indicators of success including vegetation, the propagule bank and insects. However, not all attributes delivered equivocal results. This suggests that multiple measures should be used to assess a restoration site. Anthropogenic and biophysical variables were found to influence vegetation of the restorations equally, highlighting the importance of incorporating a human component in urban ecological research. These urban restorations were seen to surpass larger rural restorations in quality; thus, efforts should be made to increase their prevalence.
437

Prairie of mine(s): engaging with the remnants of extractive processes

Baxter, Shannon D. 15 September 2008 (has links)
Prairie of Mine(s) explores the incorporation of cultural and historical elements within the reclamation of a post-industrial mining landscape in the South Saskatchewan prairie. Reclamation solely by ecological methods often fails to recognize the industrial processes and people that altered the landscape. This project utilizes experiential, cultural, and historical elements within the reclamation of mining lands to shed light on a part of our history that is frequently overlooked and draw attention to actions made on the earth everyday in order for us to live comfortably.
438

Implications of GRACE Satellite Gravity Measurements for Diverse Hydrological Applications

Yirdaw-Zeleke, Sitotaw 09 April 2010 (has links)
Soil moisture plays a major role in the hydrologic water balance and is the basis for most hydrological models. It influences the partitioning of energy and moisture inputs at the land surface. Because of its importance, it has been used as a key variable for many hydrological studies such as flood forecasting, drought studies and the determination of groundwater recharge. Therefore, spatially distributed soil moisture with reasonable temporal resolution is considered a valuable source of information for hydrological model parameterization and validation. Unfortunately, soil moisture is difficult to measure and remains essentially unmeasured over spatial and temporal scales needed for a number of hydrological model applications. In 2002, the Gravity Recovery And Climate Experiment (GRACE) satellite platform was launched to measure, among other things, the gravitational field of the earth. Over its life span, these orbiting satellites have produced time series of mass changes of the earth-atmosphere system. The subsequent outcome of this, after integration over a number of years, is a time series of highly refined images of the earth's mass distribution. In addition to quantifying the static distribution of mass, the month-to-month variation in the earth's gravitational field are indicative of the integrated value of the subsurface total water storage for specific catchments. Utilization of these natural changes in the earth's gravitational field entails the transformation of the derived GRACE geopotential spherical harmonic coefficients into spatially varying time series estimates of total water storage. These remotely sensed basin total water storage estimates can be routinely validated against independent estimates of total water storage from an atmospheric-based water balance approach or from well calibrated macroscale hydrologic models. The hydrological relevance and implications of remotely estimated GRACE total water storage over poorly gauged, wetland-dominated watershed as well as over a deltaic region underlain by a thick sand aquifer in Western Canada are the focus of this thesis. The domain of the first case study was the Mackenzie River Basin wherein the GRACE total water storage estimates were successfully inter-compared and validated with the atmospheric based water balance. These were then used to assess the WATCLASS hydrological model estimates of total water storage. The outcome of this inter-comparison revealed the potential application of the GRACE-based approach for the closure of the hydrological water balance of the Mackenzie River Basin as well as a dependable source of data for the calibration of traditional hydrological models. The Mackenzie River Basin result led to a second case study where the GRACE-based total water storage was validated using storage estimated from the atmospheric-based water balance P-E computations in conjunction with the measured streamflow records for the Saskatchewan River Basin at its Grand Rapids outlet in Manitoba. The fallout from this comparison was then applied to the characterization of the Prairie-wide 2002/2003 drought enabling the development of a new drought index now known as the Total Storage Deficit Index (TSDI). This study demonstrated the potential application of the GRACE-based technique as a tool for drought characterization in the Canadian Prairies. Finally, the hydroinformatic approach based on the artificial neural network (ANN) enabled the downscaling of the groundwater component from the total water storage estimate from the remote sensing satellite, GRACE. This was subsequently explored as an alternate source of calibration and validation for a hydrological modeling application over the Assiniboine Delta Aquifer in Manitoba. Interestingly, a high correlation exists between the simulated groundwater storage from the coupled hydrological model, CLM-PF and the downscaled groundwater time series storage from the remote sensing satellite GRACE over this 4,000 km2 deltaic basin in Canada.
439

Network evolution: the origins, development and effectiveness of Manitoba's railway system

McCombe, Christopher G. L. 13 September 2011 (has links)
This thesis examines the characteristics of railway infrastructure development and associated issues in Manitoba, Canada. The period under consideration dates from when the first tracks were laid in 1878 through to the completion of the Hudson Bay Railway in 1929. Setting the scene is a template for railway development in general, one that allows hypotheses to be drawn that are specific to Manitoba. In order to test those hypotheses it is necessary to first provide a comprehensive overview of the historical evolution of the railway network. Next, aspects of graph theory are reviewed, identifying the methodology most appropriate for a spatial analysis of railway networks. This analysis attempts to draw conclusions about the relationship between the railway companies and the governments, people and geography that they were compelled to deal with. The testing of these forms revealed that while the Manitoba railway network is very complex, it never arrived at the maximum possible complexity.
440

Black-tailed prairie dog declines in northwestern Mexico: species-habitat relationships in a changing landscape

Avila-Flores, Rafael 11 1900 (has links)
One of the three largest systems of black-tailed prairie dog (BTPD) colonies is located in northwestern Chihuahua, Mexico. During the last two decades, the area occupied by these colonies has been highly reduced and fragmented. Previous studies suggested that agriculture, poisoning, cattle overgrazing and shrub encroachment could be the factors responsible for such declines. However, the severe drought occurring in the region between 1994 and 2004 has not been considered in this equation. Because these populations occur in arid regions at the southern edge of the species range, they could be especially sensitive to changes in plant productivity. Furthermore, fragmentation of colonies may accelerate population declines due to size and isolation effects. In this study, I analyzed species-habitat relationships at different spatial and temporal scales to understand the causes of recent declines of BTPDs in northwestern Chihuahua. The most severe loss of colony area and most local extinctions occurred between 1988 and 2000, but most likely before 1997. Extinction of colonies before 2000 mostly occurred at small and isolated colonies in low-productivity areas. The coincidence of greatest area decline with the occurrence of most intense drought suggests a prominent role of drought in the population collapse. Overall, patterns of BTPD occurrence and abundance in Chihuahua are greatly influenced by spatial and temporal variation in forage cover. Although BTPDs were more likely to occur in open areas with short vegetation, increased forage cover positively predicted occurrence. High levels of forage cover during the dry season were positively related with BTPD density, juvenile production and population rate of change, but forage cover during the preceding rainy season was a negative predictor of demographic indices. High plant productivity during humid periods seems to have negative impacts on BTPD populations, presumably because the rapid plant growth reduces visibility and predator detection by BTPDs. The most influential landscape variable was the effective isolation of colonies. Although increased isolation may reduce the probability of occurrence at a given site, highly isolated locations may support high population densities. Contrary to my original predictions, I did not detect significant impacts of human-related factors on BTPD distribution and abundance. / Ecology

Page generated in 0.0297 seconds