Browsing by Subject "Monitoring"
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Item Aquifer Management for CO2 Sequestration(2010-07-14) Anchliya, AbhishekStorage of carbon dioxide is being actively considered for the reduction of green house gases. To make an impact on the environment CO2 should be put away on the scale of gigatonnes per annum. The storage capacity of deep saline aquifers is estimated to be as high as 1,000 gigatonnes of CO2.(IPCC). Published reports on the potential for sequestration fail to address the necessity of storing CO2 in a closed system. This work addresses issues related to sequestration of CO2 in closed aquifers and the risk associated with aquifer pressurization. Through analytical modeling we show that the required volume for storage and the number of injection wells required are more than what has been envisioned, which renders geologic sequestration of CO2 a profoundly nonfeasible option for the management of CO2 emissions unless brine is produced to create voidage and pressure relief. The results from our analytical model match well with a numerical reservoir simulator including the multiphase physics of CO2 sequestration. Rising aquifer pressurization threatens the seal integrity and poses a risk of CO2 leakage. Hence, monitoring the long-term integrity of CO2 storage reservoirs will be a critical aspect for making geologic sequestration a safe, effective and acceptable method for greenhouse gas control. Verification of long-term CO2 residence in receptor formations and quantification of possible CO2 leaks are required for developing a risk assessment framework. Important aspects of pressure falloff tests for CO2 storage reservoirs are discussed with a focus on reservoir pressure monitoring and leakage detection. The importance of taking regular pressure falloffs for a commercial sequestration project and how this can help in diagnosing an aquifer leak will be discussed. The primary driver for leakage in bulk phase injection is the buoyancy of CO2 under typical deep reservoir conditions. Free-phase CO2 below the top seal is prone to leak if a breach happens in the top seal. Consequently, another objective of this research is to propose a way to engineer the CO2 injection system in order to accelerate CO2 dissolution and trapping. The engineered system eliminates the buoyancy-driven accumulation of free gas and avoids aquifer pressurization by producing brine out of the system. Simulations for 30 years of CO2 injection followed by 1,000 years of natural gradient show how CO2 can be securely and safely stored in a relatively smaller closed aquifer volume and with a greater storage potential. The engineered system increases CO2 dissolution and capillary trapping over what occurs under the bulk phase injection of CO2. This thesis revolves around identification, monitoring and mitigation of the risks associated with geological CO2 sequestration.Item An evaluation of rural sanitation in India(2015-08) Mauro, Benjamin Matthew; Eaton, David J.; Weaver, CatherineOne billion people practice open defecation globally resulting in approximately 900,000 deaths via contaminated water and contact with human excreta. India is home to 600 million of the individuals engaging in open defecation, and poor sanitation is estimated to cause over 400,000 deaths annually. The Swachh Bharat Mission, the Indian government's scheme to increase sanitation coverage across India, promotes toilet construction by subsidizing the costs. The program has produced limited uptake in hygienic behavior change, and toilet construction goals are not being met. This study evaluates the effectiveness of sanitation interventions in 22 studies in the rural setting. The review identifies successful sanitation interventions and highlights gaps in the existing literature. Three types of studies were evaluated: infrastructure interventions, education interventions, and interventions that employed a combination of the two methods; and the review of the studies found that interventions utilizing community mobilization and subsidies as a part of their outreach were more likely to increase toilet coverage in the rural environment. The review also provides recommendations for future interventions, research, and implementing organizations operating in the rural sanitation environment. The report was written to inform the work of Humanure Power, an NGO working to end open defecation in rural Bihar, India. The potential for conditional cash transfers and pit latrine volumes were explored as solutions to inducing behavioral change, and the report outlined an evaluation framework for the rural environment. This report provides a framework that tracks multiple indicators and incorporates local help to build a sustainable sanitation tracking system to account for the difficulties of program monitoring and evaluation in a resource-limited environment.Item Patterns in seagrass coverage and community composition along the Texas coast : a three-year trend analysis(2015-05) Wilson, Sara Susan; Dunton, Kenneth H.; Buskey, Edward J.; Maidment, David R.Seagrasses are extremely productive coastal plant communities that serve as habitat for various types of marine and estuarine fauna and provide numerous ecosystem services. Seagrass meadows around the world have become threatened by environmental and anthropogenic pressures such as altered hydrologic regimes, physical disturbances, and eutrophication. Monitoring programs that provide high-resolution information and document changes in cover, morphometric characteristics, species composition, and tissue nutrient content across large spatial scales are critical in global conservation and management efforts. In an attempt to address the uncertainties regarding the current distribution and condition of seagrasses in the southwest Gulf of Mexico, I conducted annual sampling from 2011-2013 to examine seagrass cover and condition at 558 permanent stations. Sampling occurred in three regions of the Texas coast: the Coastal Bend (CB), Upper Laguna Madre (ULM), and Lower Laguna Madre (LLM), which together comprise over 94% of the seagrasses in Texas. Significant trends in seagrass coverage and tissue elemental composition were highly location- and species-specific. In the CB, I did not observe significant changes in seagrass cover and no spatial patterns in tissue nitrogen (N) or phosphorus (P) were apparent. However, I observed a species shift in the northern ULM, where significant decreases in Syringodium filiforme cover were coupled with significant increases in Halodule wrightii cover. Long-term salinity records at four stations throughout the study area suggest that S. filiforme mortality in the ULM in 2013 was a product of an extended period of high salinity (> 55) that began in late 2012. In LLM, there were significant increases in H. wrightii cover in the north and significant decreases in T. testudinum cover in the south, which cannot be explained based on underwater light levels, salinity, or nutrient availability. Both H. wrightii and T. testudinum displayed lower C:N, C:P, and N:P ratios, along with enriched δ¹⁵N signatures nearest urban areas, particularly in the LLM. This study illustrates the value of integrating rapid-assessment field sampling and rigorous statistical and spatial analysis into a large-scale seagrass monitoring program to uncover patterns in seagrass community structure. I detected significant trends in seagrass coverage and condition across multiple spatial and temporal scales, including a massive species replacement that coincided with a prolonged period of hypersaline conditions.Item Resilience in youth under investigation for maltreatment exposure : perceptions of support, monitoring and school engagement and the effects on self-reported delinquency(2015-08) Lamari-Fisher, Alexandra; Keith, Timothy, 1952-; Carlson, Cindy I; Sander, Janay B; Sherry, Alissa; Thompson, SannaIn national surveys of youth being investigated as potential victims of maltreatment, outcomes suggest that being involved with Child Protective Services (CPS), regardless of the final case determination, can be considered a risk event, changing youth’s life trajectory and increasing the likelihood of negative outcomes as they enter young adulthood. The negative outcomes these youth experience as young adults— increased risk of poverty, higher rates of mental health symptoms, higher rates of domestic violence—have been shown to be risk factors associated with becoming a perpetrator of child maltreatment. Applying a resiliency framework to the issue of maltreatment shifts the focus from psychopathology to positive adaptations despite risk exposure. The building blocks of the resiliency framework are protective mechanisms, variables that can shift a potentially negative life trajectory by promoting positive adaptations in three core areas of competencies: social, academic and conduct. This study was designed to examine the potential protective effects of perceived support by a caregiver, perceived monitoring, and school engagement, using delinquency as a measure of conduct competence. Support by caregiver is defined by qualities such as warmth and security, as well as supporting adolescent autonomy development. Previous research has shown that for most adolescents a positive, supportive relationship with a caregiver serves as a protective mechanism reducing the likelihood of engagement in delinquent acts. Research has shown that adolescents who are actively monitored by adult caregivers are less likely to experience negative outcomes. School engagement has more mixed results depending on the underlying components examined and the population being studied. A latent variable structural equation model (SEM) was developed and tested using a sample of 1054 youth aged 11 to 17 who were involved with Child Protective Services. Participants were drawn from the National Survey for Child and Adolescent Well-Being II (NSCAW-II). The SEM model tested the direct effects of the latent variables of perceived support, perceived monitoring, and school engagement, as measured at baseline, on overall delinquency and on subtypes of delinquency 18 months later. Results of the study suggested that higher levels of perceived support by a caregiver led to reduced reports of subsequent minor offenses. Youth who reported higher levels of monitoring by caregivers at baseline reported higher levels of offenses against persons and minor offenses 18 months later. Conversely, youth who reported higher levels of school engagement at baseline reported significantly lower levels of offenses against people and property and fewer minor offenses 18 months later. Results of this study highlight the important role schools play as a resource for at-risk youth, supporting positive adaptation. The unexpected outcomes associated with monitoring imply how and when monitoring is measured can affect delinquency.Item Study in smart monitoring of the quality of VoIP services(2010-08) Chi, Sanghyun; Baldick, Ross; Womack, Baxter F., 1930-; Swartzlander, Earl; Ghosh, Joydeep; Caramanis, Constantine; Wilson, Preston S.; Kim, Doh-SukOver the last decade, the internet industry has rapidly grown with regard to infrastructure and bandwidth. Widespread internet networks with large bandwidth connect people-to-people, people-to-machines, and machine-to-machine. Like other multimedia services, large bandwidth enables voice services to be provided over IP networks where network connectivity is not consistent. In this context, research on service quality monitoring is necessary to satisfy customers by providing consistent service quality. The major contribution of this dissertation is the development of three novel techniques to improve or measure voice quality over IP networks. This dissertation first addresses an adaptive playout buffer scheduling algorithm that enables systems to lossen delay jitter due to the legacy of packet-switched networks. The scheduling algorithm is operated by a desired quality of service, minimizing the end-to-end delay by adjusting playout delay times. Secondly, this dissertation also explores a parameter-based nonintrusive speech quality measure to monitor the quality of VoIP. During the lifetime of sound, the network parameters are estimated and used to predict the quality of speech. As a cognitive model, a machine-learning technique is exploited to map features in the feature space into the perceived speech quality scale space. Finally, this dissertation introduces a signal-based nonintrusive speech quality measure. Features for the proposed measurement are extracted from observations of the characteristics of natural speech sounds and artificial noises. The calculated features are mapped into the perceived speech quality scale. The proposed parameter-based measure achieves a high prediction accuracy while the signal-based measure reaches to a comparable performance to the official International Telecommunication Union (ITU) standard, P.563. The contributions described in this dissertation provides smart methodologies for monitoring or enhancement of VoIP service qualities.Item The maximum time interval of time-lapse photography for monitoring construction operations(Texas A&M University, 2005-11-01) Choi, Ji WonMany construction companies today utilize webcams on their jobsites to monitor and record construction operations. Jobsite monitoring is often limited to outdoor construction operations due to lack of mobility of wired webcams. A wireless webcam may help monitor indoor construction operations with enhanced mobility. The transfer time of sending a photograph from the wireless webcam, however, is slower than that of a wired webcam. It is expected that professionals may have to analyze indoor construction operations with longer interval time-lapse photographs if they want to use a wireless webcam. This research aimed to determine the maximum time interval for time-lapse photos that enables professionals to interpret construction operations and productivity. In order to accomplish the research goal, brickwork of five different construction sites was videotaped. Various interval time-lapse photographs were generated from each video. Worker?s activity in these photographs was examined and graded. The grades in one-second interval photographs were compared with the grades of the same in longer time interval photographs. Error rates in observing longer time-lapse photographs were then obtained and analyzed to find the maximum time interval of time-lapse photography for monitoring construction operations. Research has discovered that the observation error rate increased rapidly until the 60-second interval and its increasing ratio remained constant. This finding can be used to predict a reasonable amount of error rate when observing time-lapse photographs less than 60-second interval. The observation error rate with longer than 60-second interval did not show a constant trend. Thus, the 60-second interval could be considered as the maximum time interval for professionals to interpret construction operations and productivity.