Browsing by Subject "Vulnerability"
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Item Analyses of power system vulnerability and total transfer capability(Texas A&M University, 2006-04-12) Yu, XingbinModern 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.Item Assessing impacts of hydroelectric dams in the Amazon Fluvial Basin(2015-05) Wight, Charles Edward; Latrubesse, Edgardo; Arima, EugenioThe amount of water the Amazon River delivers to the Atlantic Ocean every day is enough to supply New York City's fresh water needs for 9 years. This is soon to change with the race to choke the Amazon Basin with large hydrologic dams. Although studies investigating single dams can provide great analysis on a couple key issues, they often fail to consider these effects on the systems entirety. Without linking the physical and social components, one fails to fully understand the impacts of hydroelectric dams and therefore the vulnerability of the basin. The focus of this study is based on three forms of investigation: 1. a comprehensive literature review including scholarship on hydroelectric dams, basis characteristics, protected areas, and political characteristics within the respective countries; 2. data procurement of the physical geography of 20 sub-basins, 1,100 tributaries, and land use-land change (LULC) data; and together 3. the creation of a multivariable database integrated with GIS (geographic information systems) in order to better interpret human/nature complexities. Combined, this database will be a powerful tool to assess vulnerability and risks associated with individual dams sites within a larger system. In addition, this database can be adjusted in the future such that when impacts of planned dams are actualized they can be recorded, and based of shared attributes of other dams in the database, this information can be correlated to make better predictions of new environmental and social impacts.Item The changing climate of vulnerability, aid and governance in Malawi(2012-05) Malcomb, Dylan Wayne; Crews, Kelley A.; Young, Kenneth R.; Miller, Jennifer A.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.Item Development and validation of the cognitive vulnerability schemas questionnaire for anxious youth(2014-12) Winton, Samantha Marie; Stark, Kevin DouglasAccording 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.Item God, children and country : an in-depth study of the condition of immigrant illegality through the experiences of Mexican domestic workers in Dallas, Texas(2015-08) Lugo, Betsabeth Monica; Rudrappa, Sharmila, 1966-; Rodriguez, Nestor; Young, Michael; Gonzalez-Lopez, Gloria; Cuellar, GregoryIn this dissertation I examine the lived experiences of 43 undocumented Mexican women working in the Dallas-Fort Worth area, particularly, the ways that these women navigate and make sense of what I identify as environments of vulnerability -social contexts characterized by local configurations of migrant “illegality” (a paradigm-in-progress). In Article 1, I analyze three in-depth interviews with undocumented Mexican domestics to understand how they use religious stories and symbols to help them make sense of and cope with the uncertainties and vulnerabilities they face living in the United States. Findings from this article indicate that women 1) draw from religious discourses to actively interact with their social environments and 2) construct narratives that allow them to create an alternative version of the social world and a coherent sense of self. These findings contribute to a nuanced understanding of the ways that religion shapes undocumented immigrant women’s lives outside of religious institutions and religious contexts. In Article 2, I examine the strategies that 40 undocumented Mexican women use to mother in environments of vulnerability. Findings from this article reveal that these women use two key strategies to protect their children’s well-being: 1) moving out of neighborhoods with undesirable “others” (i.e., the poor, Blacks, and “less worthy” Mexican immigrants) and 2) withholding information from their children regarding their legal status. These findings contribute to an increased understanding of the mothering practices of women who face multiple structural oppressions. Finally, in Article 3 I examine the factors that influence undocumented Mexican women’s decisions to stay in the United States, even as they face the uncertainty associated with deportability -- that is, even as they traverse environments of vulnerability. Two factors primarily underlie women’s decision to stay in the U.S.: the availability of quality public education and educational opportunities for their children and the fear that they or their children will be the targets of violence in Mexico. These findings add to research on family and migration and extend previous research to reveal how Mexican women and their children navigate the shifting terrain of state power as they build their lives in the United States.Item Integrated Drought Modeling For Texas Under Climate Change Impact With Implications For Water Resources Planning(2014-12-02) Rajsekhar, DeepthiDrought is a deficiency in the hydro climatic variable of interest that is experienced for an extended period of time. In many parts of the world, it is a normal, recurring feature of climate and is therefore inevitable. Adequate monitoring and planning is required for effective mitigation of droughts. The study area for this research is Texas, which has been a consistently drought prone state. There has been at least one serious drought in one part of the state or the other during every decade of the twentieth century. This trend is likely to increase in the coming years due to the effect of global warming and climate change. Taking into account the importance of water management under conditions of extreme climate, this study focuses on enhancing various aspects of drought modeling. The major goals include the development of an efficient means to quantify multiple physical forms of drought, formulation of scientifically robust drought planning regions, integrated multivariate hazard and vulnerability assessment under climate change impact, understanding the causal factors that might trigger a drought event in future, and development of an effective interface to convey the research results to decision makers. These goals were designed to bridge the gaps existing in the current drought research, which even though substantial, still fails to address some of the issues. The goals are addressed by developing a new multivariate drought index, use of copula to build the dependence structure of drought properties and subsequent plotting of multivariate risk maps, development of Drought Hazard Index (DHI) and Drought Vulnerability Index (DVI) for integrated risk analysis under climate change impact, and use of Directional Information Transfer (DIT) for grouping of homogeneous drought regions. A novel transfer entropy approach is adopted to analyze the cause-effect relationship between various hydro-climatic variables and drought properties, thus identifying the prominent future drought triggers. Finally, an efficient drought Decision Support System (DSS) is developed to convey the research results to decision makers through a number of statistical techniques and effective visualization. Ultimately, the study aims at developing a comprehensive framework for better understanding of droughts in Texas which will help decision makers to formulate a more effective adaptation and mitigation strategy in future.Item (Re)interpreting vulnerabilities in the peri-urban Valley of Mexico : toward a deeper and more actionable understanding of poverty in Mexico City’s urban fringe(2014-08) Siegel, Samuel Donal; Dooling, SarahSettlement patterns on the urban fringe can present a host of threats to sociopolitical and biophysical sustainability, at the personal, municipal, and ecosystem scale. Mexico City’s expansive growth has forced the region’s poorest inhabitants to the farthest margins in the neighboring State of Mexico, where they often live in conditions of personal hardship and settle in patterns that threaten the ecological health of environmentally sensitive areas. Following interviews with practitioners in three periurban municipalities in the Valley of Mexico, this report examines how local land use regulators interpret the vulnerabilities facing communities in their jurisdictions and presents a typology of vulnerabilities. The report explores the processes of politicization that produce and re-produce the vulnerabilities facing individuals, communities and ecosystems. Several concrete policy recommendations are made for incorporating holistic thinking about vulnerability into government decision-making, and resources are provided for further research.Item Vulnerability and decision risk analysis in glacier lake outburst floods (GLOF). Case studies : Quillcay sub basin in the Cordillera Blanca in Peru and Dudh Koshi sub basin in the Everest region in Nepal(2014-08) Somos-Valenzuela, Marcelo A.; McKinney, Daene C.Glacial-dominated areas pose unique challenges to downstream communities in adapting to recent and continuing global climate change, including increased threats of glacial lake outburst floods (GLOFs) that have substantial impacts on regional social, environmental and economic systems increasing risk due to flooding of downstream communities. In this dissertation, two lakes with potential to generate GLOFs were studied, Imja Lake in Nepal and Palcacocha Lake in Peru. At Imja Lake, basic data was generated that allowed the creation of a conceptual model of the lake. Ground penetrating radar and bathymetric surveys were performed. Also, an inundation model was developed in order to evaluate the effectiveness of a project that seeks to reduce flooding risk by lowering the lake at least 3 meters. In Peru, a GLOF inundation model was created. Also, the vulnerability of the people living downstream in the City of Huaraz was calculated, and the impacts of an early warning system were evaluated. The results at Imja indicated that the lake deepened from 98 m in 2002 to 116 m in 2012. Likewise, the lake volume increased from 35.8 to 61.6±1.8 million m3 over the past decade. The GPR survey at Imja and Lhotse-Shar glaciers shows that the glacier is over 200 m thick in the center of the glacier. The modeling work at Imja shows that the proposed project will not have major impacts downstream since the area inundated does not reduce considerably unless the lake is lowered by about 20 m. In Huaraz, the results indicate that approximately 40646 people live in the potentially inundated area. Using the flow simulation and the Peru Census 2007, a map of vulnerability was generated indicating that the most vulnerable areas are near the river. Finally, the potential number of fatalities in a worst case GLOF scenario from Lake Palcacocha was calculated to be 19773 with a standard deviation of 1191 if there is no early warning system and 7344 with a standard deviation of 1446 people if an early warning system is installed. Finally, if evacuation measures are improved the number reduces to 2865 with a standard deviation of 462.Item Vulnerability assessment of water supply systems for insufficient fire flows(2009-05-15) Kanta, Lufthansa RahmanWater supply systems? vulnerability towards physical, chemical, biological, and cyber threats was recognized and was under study long before September 11, 2001. But greater attention toward security measures for water supply systems was focused after the incidents of September 11, 2001. In response to those events, several acts have been passed by the United States Congress, and numerous vulnerability assessment tools and methodologies for water systems have been developed. Although water supply systems are vulnerable to many forms of terrorist acts, most of the vulnerability analysis studies on these systems have been for chemical and biological threats. Because of the interdependency of water supply infrastructure and emergency fire response, any substantial damage in a water system would be a significant threat towards the community. In this study, attention is focused toward physical threats on water supply systems during a fire flow condition, and a methodology is developed to determine the vulnerable components of a water supply system during a fire event. The methodology utilizes dynamic programming optimization procedure to determine maximized disruption of fire flows as a function of number of attacks and/or failures in the water distribution system. Disruption is quantified at specific fire hydrants in two schemes using normalized values of (1) available flow and (2) available pressure and distance to the nearest operational fire hydrant. It is found that the pressure-based quantity is inferior to the flow-based one. However, using the flow-based disruption metric, clear functions of disruption versus failure number can be determined that exhibit discernable properties of robustness and resiliency ? and the sequential failures in each. This methodology is applied to the water supply system of Micropolis, a virtual city developed by Brumbelow et al. (2005), and vulnerability analysis is performed with fire at several possible locations. On the basis of the results, three mitigation strategies are proposed to harden specific sets of water mains and more simulations are performed on the hardened water supply system to assess its changed vulnerability. The results from the simulations of the mitigation strategies show that the recommendations on specific mitigation measures reduce the serious consequences from such threats.