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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.
71

Analyses of power system vulnerability and total transfer capability

Yu, Xingbin 12 April 2006 (has links)
Modern power systems are now stepping into the post-restructuring era, in which utility industries as well as ISOs (Independent System Operators) are involved. Attention needs to be paid to the reliability study of power systems by both the utility companies and the ISOs. An uninterrupted and high quality power is required for the sustainable development of a technological society. Power system blackouts generally result from cascading outages. Protection system hidden failures remain dormant when everything is normal and are exposed as a result of other system disturbances. This dissertation provides new methods for power system vulnerability analysis including protection failures. Both adequacy and security aspects are included. The power system vulnerability analysis covers the following issues: 1) Protection system failure analysis and modeling based on protection failure features; 2) New methodology for reliability evaluation to incorporate protection system failure modes; and, 3) Application of variance reduction techniques and evaluation. A new model of current-carrying component paired with its associated protection system has been proposed. The model differentiates two protection failure modes, and it is the foundation of the proposed research. Detailed stochastic features of system contingencies and corresponding responses are considered. Both adequacy and security reliability indices are computed. Moreover, a new reliability index ISV (Integrated System Vulnerability) is introduced to represent the integrated reliability performance with consideration of protection system failures. According to these indices, we can locate the weakest point or link in a power system. The whole analysis procedure is based on a non-sequential Monte Carlo simulation method. In reliability analysis, especially with Monte Carlo simulation, computation time is a function not only of a large number of simulations, but also time-consuming system state evaluation, such as OPF (Optimal Power Flow) and stability assessment. Theoretical and practical analysis is conducted for the application of variance reduction techniques. The dissertation also proposes a comprehensive approach for a TTC (Total Transfer Capability) calculation with consideration of thermal, voltage and transient stability limits. Both steady state and dynamic security assessments are included in the process of obtaining total transfer capability. Particularly, the effect of FACTS (Flexible AC Transmission Systems) devices on TTC is examined. FACTS devices have been shown to have both positive and negative effects on system stability depending on their location. Furthermore, this dissertation proposes a probabilistic method which gives a new framework for analyzing total transfer capability with actual operational conditions.
72

Sustainable forests: A strategy for climate change adaptation and mitigation? : A case study from Babati District, Tanzania

Hall, Elin January 2009 (has links)
This Bachelor‟s thesis aims at explaining the relationship between forests and climate change, a subject that has been given a lot of attention in environmental discussions in recent years, particularly because forests are a source of carbon dioxide emissions and in the same time have the potential to mitigate climate change through carbon sequestration. However, with the importance of mitigation as a background, the focus of this study is on adaptation. The purpose is to identify mutual benefits from the diverse forest ecosystems, and examine the possible benefits from forests to the rural poor population in Tanzania, in a future scenario of increased vulnerability to climate change. The methodology for the study can be divided into two parts, one qualitative literature study and one field study in Babati District northern Tanzania, limited to interviews and excursions. This thesis gives details about the scientific projections and local perceptions of climate change and the effects of climate change. The results of the thesis highlights the importance of sustainably managed forests and agroforestry systems, which have been successful in Babati through local participation; economic incentives such as carbon credit and other payments for ecosystem services, which is a possible future extension of forestry activities; and increased integration between sectors, which make sure that adaptation within different sectors can be done simultaneously.
73

Coastal Vulnerability to Storms in the Catalan Coast

Mendoza Ponce, Ernesto Tonatiuh 28 March 2008 (has links)
Este trabajo presenta un marco metodológico para la estimación de la vulnerabilidad costera al impacto de tormentas a dos escalas, regional y local. Se hace una evaluación de la vulnerabilidad costera física mediante la cuantificación de dos componentes: erosión e inundación. Posteriormente, ambos elementos son integrados en un Índice de Vulnerabilidad Costera. La metodología desarrollada cubre los siguientes pasos: (i) clasificación de tormentas, (ii) evaluación de la respuesta inducida en la playa -inundación y erosión- (iii) caracterización de las playas en la zona de estudio (iv) definición del índice de vulnerabilidad costera y (v) evaluación de la vulnerabilidad costera. Estos pasos han sido derivados y aplicados a la costa catalana (Mediterráneo Noroccidental español) y pueden ser adaptados a otras costas. Los resultados obtenidos pueden ser fácilmente utilizados por los gestores costeros para identificar zonas costeras sensibles a una clase de tormenta dada y sus procesos inducidos (inundación, erosión o la combinación de ambos) para decidir donde tomar acciones para mitigar estos impactos. / This work presents a methodological framework for the estimation of coastal vulnerability to storm impacts at two scales, regional and local. It estimates the physical coastal vulnerability through the quantification of two components: erosion and flooding. Afterwards the two elements are integrated into the so called Coastal Vulnerability Index. The methodological process covers the following steps: (i) storm classification, (ii) evaluation of the induced beach response -flood and erosion-, (iii) coastal zone characterization, (iv) definition of a coastal vulnerability index to storms and (v) assessment of the coastal vulnerability. These steps have been derived and applied to the Catalan coast (NW Spanish Mediterranean) and can be adapted to other coasts. The obtained results can be used by coastal managers in an easy manner to identify sensitive coastal stretches for a given storm class and the induced processes (flooding, erosion or combination of both) with the purpose to take actions and mitigate these impacts.
74

Evaluating Regional Aquifer Vulnerability and BMP Performance in an Agricultural Environment Using a Multi-Scale Data Integration Approach

Koch, Jamie 19 June 2009 (has links)
The increased use of both organic and synthetic fertilizers on agricultural land has lead to rising groundwater nitrate concentrations in some areas of southern Ontario. This has occurred at the Thornton Well Field in Oxford County, likely as a result of impacts from legacy agricultural activities in the area. In an attempt to mitigate the impact on water quality within the well field, the County purchased some of the agricultural land in the vicinity of the well field in 2001 with plans to reduce nutrient loading through the implementation of Beneficial Management Practices (BMPs). Since the initiation of the BMPs, the nitrogen application rates within the study site were reduced by 20 to 100% relative to historical rates. The objectives of this study were to provide a unique, five year data set which can assist in BMP development and provide direction for regional scale agricultural policy; evaluate the nitrate mass flux at numerous locations through the unsaturated zone beneath a BMP-activated agricultural field within a complex moraine environment; develop and compare various methods to upscale point measurements of mass flux to mass loading (t N03-N/yr) at the field and regional scale; evaluate standardized methods of assessing aquifer vulnerability and compare results within the context of non-point source agricultural contaminants at the field and regional scale; and determine whether monitoring water levels and temperature within monitoring wells is able to aid in evaluating vulnerability to surface contaminants. Information collected over two years was combined with data gathered by former researchers at the field site to create a unique and extensive data set. Nineteen new monitoring wells, including two Continuous Multilevel Tubes (CMT), were installed to further develop the geological conceptual model and identify crucial discontinuities in the aquitard units. This network was devised and installed by a team of hydrogeologists. Eight geologically and topographically diverse monitoring locations or “stations” had been previously established and monitored by Bekeris (2007) to track changes in soil nitrate mass within the unsaturated zone through successive geologic coring. This study involved the selection of seven new locations that were predicted to behave similarly to one of the original eight stations in order to assess the predictive capability of scaling up point measurements. The upscaling criteria were based primarily on near surface geology, topography and field observations, with the former being determined as exerting the greatest influence on the results. Recharge rates estimates were combined with unsaturated zone soil nitrate data obtained from geologic coring events to produce nitrate mass flux estimates. Four methods of scaling up point estimates of mass flux made at fourteen of the stations to produce mass loading estimates across the whole field site were compared. The best method displayed nitrate mass loading having decreased within Parcel B from 6.77 t/yr in May 2006 to 2.55 t/yr in May 2008 resulting in a total mass reduction rate of 4.20 t/yr or 62 % which verifies the effectiveness of the BMPs. This corresponds well with the 46% decrease in applied nitrogen associated with the BMP. Groundwater quality measured using standard monitoring wells with long screens indicated that nitrate concentrations have ceased to increase, while groundwater taken from the discrete sampling ports of the CMT wells shows significantly lower concentrations of nitrate within the ports located closer to the water table. This further validates the success of the BMPs but suggests that there is a long lag time between BMP implementation and the flushing of deeper aquifer zones with cleaner, recharging water. Despite the decrease in applied nitrogen, crop yields have remained at or above historical values. Three commonly applied vulnerability assessment methods including the Aquifer Vulnerability Index (AVI), Intrinsic Susceptibility Index (ISI) and Surface to Aquifer Advection Time (SAAT) were utilized to rank the vulnerability of the Thornton Well Field to surface contaminants. The results highlighted how complex hydrogeology may result in inconsistent rankings of vulnerability by each of the methods. The results from analyzing temperature and pressure data collected from pressure transducers within wells across the site suggest that these data can verify and improve the results from standardized vulnerability assessment techniques, especially during highly vulnerable snow melt events.
75

Evaluating Regional Aquifer Vulnerability and BMP Performance in an Agricultural Environment Using a Multi-Scale Data Integration Approach

Koch, Jamie 19 June 2009 (has links)
The increased use of both organic and synthetic fertilizers on agricultural land has lead to rising groundwater nitrate concentrations in some areas of southern Ontario. This has occurred at the Thornton Well Field in Oxford County, likely as a result of impacts from legacy agricultural activities in the area. In an attempt to mitigate the impact on water quality within the well field, the County purchased some of the agricultural land in the vicinity of the well field in 2001 with plans to reduce nutrient loading through the implementation of Beneficial Management Practices (BMPs). Since the initiation of the BMPs, the nitrogen application rates within the study site were reduced by 20 to 100% relative to historical rates. The objectives of this study were to provide a unique, five year data set which can assist in BMP development and provide direction for regional scale agricultural policy; evaluate the nitrate mass flux at numerous locations through the unsaturated zone beneath a BMP-activated agricultural field within a complex moraine environment; develop and compare various methods to upscale point measurements of mass flux to mass loading (t N03-N/yr) at the field and regional scale; evaluate standardized methods of assessing aquifer vulnerability and compare results within the context of non-point source agricultural contaminants at the field and regional scale; and determine whether monitoring water levels and temperature within monitoring wells is able to aid in evaluating vulnerability to surface contaminants. Information collected over two years was combined with data gathered by former researchers at the field site to create a unique and extensive data set. Nineteen new monitoring wells, including two Continuous Multilevel Tubes (CMT), were installed to further develop the geological conceptual model and identify crucial discontinuities in the aquitard units. This network was devised and installed by a team of hydrogeologists. Eight geologically and topographically diverse monitoring locations or “stations” had been previously established and monitored by Bekeris (2007) to track changes in soil nitrate mass within the unsaturated zone through successive geologic coring. This study involved the selection of seven new locations that were predicted to behave similarly to one of the original eight stations in order to assess the predictive capability of scaling up point measurements. The upscaling criteria were based primarily on near surface geology, topography and field observations, with the former being determined as exerting the greatest influence on the results. Recharge rates estimates were combined with unsaturated zone soil nitrate data obtained from geologic coring events to produce nitrate mass flux estimates. Four methods of scaling up point estimates of mass flux made at fourteen of the stations to produce mass loading estimates across the whole field site were compared. The best method displayed nitrate mass loading having decreased within Parcel B from 6.77 t/yr in May 2006 to 2.55 t/yr in May 2008 resulting in a total mass reduction rate of 4.20 t/yr or 62 % which verifies the effectiveness of the BMPs. This corresponds well with the 46% decrease in applied nitrogen associated with the BMP. Groundwater quality measured using standard monitoring wells with long screens indicated that nitrate concentrations have ceased to increase, while groundwater taken from the discrete sampling ports of the CMT wells shows significantly lower concentrations of nitrate within the ports located closer to the water table. This further validates the success of the BMPs but suggests that there is a long lag time between BMP implementation and the flushing of deeper aquifer zones with cleaner, recharging water. Despite the decrease in applied nitrogen, crop yields have remained at or above historical values. Three commonly applied vulnerability assessment methods including the Aquifer Vulnerability Index (AVI), Intrinsic Susceptibility Index (ISI) and Surface to Aquifer Advection Time (SAAT) were utilized to rank the vulnerability of the Thornton Well Field to surface contaminants. The results highlighted how complex hydrogeology may result in inconsistent rankings of vulnerability by each of the methods. The results from analyzing temperature and pressure data collected from pressure transducers within wells across the site suggest that these data can verify and improve the results from standardized vulnerability assessment techniques, especially during highly vulnerable snow melt events.
76

Vulnerability to Climate Related Events: A Case Study of the Homeless Population in Waterloo Region

de Gomez, Wendy January 2010 (has links)
Waterloo Region (population 470,000) is the eleventh largest urban region in Canada (2006 Census tract). Within this region, in 2007, 2,831 homeless people defined as commonly living or sleeping in indoor or outdoor spaces not intended for inhabitation used emergency shelters (Homelessness and Housing Group, 2008; Regional Municipality of Waterloo Region, 2007). It is expected that individuals who have inadequate or no permanent housing are particularly exposed and sensitive to environmental conditions such as extreme heat, cold events and poor air quality. Under climate change, it can be expected that the frequency of extreme events and days when air quality fails to meet healthy guidelines may increase. A wide survey of literature from environmental issues related to homelessness in first world countries has demonstrated that there is a research gap in understanding how urban citizens experiencing or facing homelessness adapt to environmental change. Therefore, this research addresses this gap by using both the vulnerability approach to local climate change assessments, and participatory action research to better understand the specificities of adaptation, the available services and future institutional strategies that could enhance the lives of this vulnerable population in relation to local environmental change. The conclusion is that people experiencing homelessness in Waterloo Region have a low vulnerability to climate related events as the social service system which they use is well developed and the climate related events are not severe. However, the vulnerability may increase in the future if service provision changes or if there is an increase in the duration, intensity and frequency of precipitation (rain) or extreme heat days.
77

Analyses of power system vulnerability and total transfer capability

Yu, Xingbin 12 April 2006 (has links)
Modern power systems are now stepping into the post-restructuring era, in which utility industries as well as ISOs (Independent System Operators) are involved. Attention needs to be paid to the reliability study of power systems by both the utility companies and the ISOs. An uninterrupted and high quality power is required for the sustainable development of a technological society. Power system blackouts generally result from cascading outages. Protection system hidden failures remain dormant when everything is normal and are exposed as a result of other system disturbances. This dissertation provides new methods for power system vulnerability analysis including protection failures. Both adequacy and security aspects are included. The power system vulnerability analysis covers the following issues: 1) Protection system failure analysis and modeling based on protection failure features; 2) New methodology for reliability evaluation to incorporate protection system failure modes; and, 3) Application of variance reduction techniques and evaluation. A new model of current-carrying component paired with its associated protection system has been proposed. The model differentiates two protection failure modes, and it is the foundation of the proposed research. Detailed stochastic features of system contingencies and corresponding responses are considered. Both adequacy and security reliability indices are computed. Moreover, a new reliability index ISV (Integrated System Vulnerability) is introduced to represent the integrated reliability performance with consideration of protection system failures. According to these indices, we can locate the weakest point or link in a power system. The whole analysis procedure is based on a non-sequential Monte Carlo simulation method. In reliability analysis, especially with Monte Carlo simulation, computation time is a function not only of a large number of simulations, but also time-consuming system state evaluation, such as OPF (Optimal Power Flow) and stability assessment. Theoretical and practical analysis is conducted for the application of variance reduction techniques. The dissertation also proposes a comprehensive approach for a TTC (Total Transfer Capability) calculation with consideration of thermal, voltage and transient stability limits. Both steady state and dynamic security assessments are included in the process of obtaining total transfer capability. Particularly, the effect of FACTS (Flexible AC Transmission Systems) devices on TTC is examined. FACTS devices have been shown to have both positive and negative effects on system stability depending on their location. Furthermore, this dissertation proposes a probabilistic method which gives a new framework for analyzing total transfer capability with actual operational conditions.
78

The changing climate of vulnerability, aid and governance in Malawi

Malcomb, Dylan Wayne 19 July 2012 (has links)
By year 2020, developed countries pledged to mobilize USD100 billion per year towards mitigation of greenhouse gases and strategies of adaptation. This redistribution from Annex I (developed) countries to developing countries represents a near doubling of current official development assistance levels, yet future strategies of adaptation remain nebulous. Definitions, opinions and agendas of adaptation have evolved into new global development strategy, but will externally-designed strategies threaten an adaptive process that should be community-led and environmentally-contextual? Little empirical research has been conducted on adaptation as an international development strategy that consists of massive earmarking of funds to institute and later demonstrate that projects are related to climate change. Through semi-structured interviews with international and development organizations, national and local governments, civil society and community focus groups, this research chronicles Malawi's polycentric response to climate change vulnerability. Using site-visits to numerous active adaptation projects in Malawi as case-studies, this research examines who the stakeholders are in this process, what adaptation looks like and how the overall concept of this new development strategy can be improved. / text
79

Clash of the built and natural environments : a vulnerability index to flood risk in Galveston County, Texas

Kellerman, Frances Anne 17 December 2013 (has links)
Vulnerability occurs at the intersection of natural geophysical forces and human settlement decisions. When humans decide to place themselves and their homes in harm’s way and disinvest in mitigation measures, vulnerability ensues. Human decisions have and continue to play a large role in furthering vulnerability, especially in coastal communities. With roughly 50 percent of the United States’ population currently located on the coast and with rapid development only projected to continue, coastal communities will be faced with a future of exacerbated flood events that will result in increased surface runoff, flooding, and economic losses. This report focuses on better understanding how the build environment exacerbates coastal vulnerability. This research involves the creation of a spatial vulnerability index to flood risk for Galveston County which uncovers the degree with which the built environment is exposed to flood risk and how this vulnerability can be responded to in a manner that builds coastal resiliency. / text
80

Development and validation of the cognitive vulnerability schemas questionnaire for anxious youth

Winton, Samantha Marie 09 February 2015 (has links)
According to cognitive theories of anxiety, anxiogenic schemata are a set of beliefs, rules, and assumptions that influence how those with anxiety make inferences and interpret threat. It is hypothesized that each anxiety disorder has a unique anxiogenic schema. This report describes the development of the Cognitive Vulnerability Schemas Questionnaire for Anxious Youth, an instrument used to measure anxiogenic schemata in youth aged 7-17 years old. Factor analyses of the scale demonstrated two empirically distinct and relatively stable dimensions of anxiogenic schema. The two identified factors of anxiogenic schema were: (1) Generalized Anxiety and Social Phobia Schema, and (2) Separation Anxiety Schema. The measure demonstrated good psychometric properties on a range of indices of reliability and validity. Results indicated that scores on the questionnaire subscales predicted anxiety symptomology. Regression analyses showed that both factors were predictors of anxiety symptomology, however did not predict anxiety diagnosis. Significant differences in the Cognitive Vulnerability Schemas Questionnaire for Anxious Youth subscales were demonstrated between patients with clinically significant Generalized Anxiety Symptoms, Social Phobia Symptoms, and Separation Anxiety Symptoms. The implications of these findings for theories of cognitive vulnerability and schema development in youth are discussed. / text

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