Texas A&M University-Kingsville: AKM Digital Repository
Not a member yet
1689 research outputs found
Sort by
Understanding inconsistencies and implications of global surface water extent estimates
No full textThe abundant surface water storage systems in a landscape, including lakes, ponds, wetlands, and other small depressional storages, are “non-structural” natural features. These natural infrastructures provide a wide range of ecosystem services including maintenance of biodiversity, nutrient cycle regulation, sequestering carbon, water quality improvement, along with many socio-economic benefits. However, despite the tremendous importance of these surface water systems, these natural infrastructures are vulnerable to widespread conversion and destruction due to both natural and anthropogenic stressors. To adopt effective policy and management strategies for minimizing these conversions, and thereby improve the earth’s overall resilience to climate and anthropogenic disturbances, we must develop the capability to precisely and efficiently map surface water storages and their temporal dynamics. To this end, this thesis is the first study to (i) derive surface water occurrence and surface water extent estimates from a remotely sensed near-real time, temporally continuous, fine resolution land cover dataset (objective 1), and (ii) compare the consistency and conclusivity of the new estimates with existing prominent datasets of global surface water dynamics (objective 2). The outcomes are 10-m spatial resolution global surface water occurrence and permanent and seasonal surface water extent estimates providing novel insights into readily available freshwater resources. Next, this thesis hypothesizes that currently available GSWE datasets have many structural and spatial differences; there is a large variability in the way surface waterbody extents are perceived and estimated by different global datasets. This is tested by (iii) assessing and gathering details about the varying origins and approaches of different available GSWE datasets (objective 3), and (iv) quantifying the uncertainties in GSWE by mapping and estimating the variation in extent and count of waterbodies across the selected GSWE datasets (objective 4). Results suggest that the inconsistencies across GSWE datasets stem mainly from their underlying definition of surface waters, data format, and data sources and methods used for waterbody delineation. In summary, GSWE datasets are critical to understanding the availability and implications of global water resource variations, especially under a changing climate. However, without ensuring accuracy and consistency in today’s GSWE datasets, a stride towards sustainable water resources may not be meaningful. This work is an attempt to address these needs
On the ecology and management of whitebrush (Aloysia gratissima) with considerations towards climate variability
No full textManagement of noxious shrubs has been a common practice on South Texas, USA rangelands since the early 1800’s. An increase in woody plants on landscapes historically dominated by herbaceous plant communities alters the structure and function of the landscape, affecting ecosystem services and potential economic profit. Whitebrush (Aloysia gratissima) is a native shrub in South Texas that exhibits locally noxious behavior, forming monoculture stands that often require intensive management. Until recently, management options were limited to soil-applied herbicides and mechanical tools, which have proven ineffective for offering long-term control due to the vegetation propagation capabilities of the belowground root crown. Whitebrush's drought tolerant behavior (defoliation in response to moisture stress) limits the traditional window of opportunity for foliar herbicide applications. Recent developments have approved a new active chemical (Invora) in the picolinic acid family for use in rangelands capable of offering high levels of control for resprouting woody species. Our goal was to inform upon the current recommended chemical management options and evaluate novel dormant season treatments for controlling whitebrush in South Texas through two herbicide field experiments. Additionally, we evaluated viable seed production and germination rates through laboratory and greenhouse experiments to provide insight into population re-establishment. Our field trials showed that aminocyclopyrachlor + triclopyr (ACP + T 1:2) provided high levels of control when applied as individual plant (IPT, mortality = 99.98%) and broadcast (BC, mortality = 81.97%) foliar treatments regardless of season (p = 0.29, α = 0.05) two years after treatment. We also found that foliar-like applications can be highly effective when applied to dormant shrubs (IPT mortality = 99.98%, BC mortality = 81.97%) without increasing the percent volume of surfactant in the chemical mix (p = 0.77, α = 0.05). Results from laboratory testing indicated variation in the percent of viable seed produced annually between populations (6% - 49%), providing insight into population recruitment strategies post-treatment
Passive and active suspension control systems analysis and design
No full textSuspension systems are a crucial part of modern vehicles/cars. It is a necessary part to keep the vehicle tires or wheels in contact with the road when disturbances occur. They are meant to provide comfort, stability, and safety to the passengers by filtering the road disturbances. This research paper focuses on passive suspension system which work without any external source and by pointing out the drawbacks in it and also active suspension system which works with the help of external source.
Passive suspension systems use springs and dampers for energy absorption and dissipation caused by road-induced vibrations. This study investigates the dynamic behaviour of passive and active suspension systems for varied road profiles utilizing MATLAB Simulink for simulation and a variety of driving circumstances. Key performance metrics like body displacement, acceleration, suspension deflection and ride comfort are analysed to evaluate their effectiveness.
By providing a detailed analysis of passive suspension systems and active suspension systems, this study contributes to analyse the suspension design and serves as the fundamental for future advancements in the automotive suspension designs and lay a foundation for the passive, active suspension systems advancements
Genomic insights into endangered ocelot (Leopardus pardalis) populations to inform species recovery
No full textWith habitat and species loss occurring at unprecedented rates, conservation action is needed to preserve threatened and endangered populations. Habitat loss and fragmentation isolate populations, which can result in increased susceptibility to stochastic events such as severe weather or disease. Small populations are also vulnerable to loss of genetic diversity due to genetic drift and inbreeding, both of which can reduce fitness. Reintroduction can increase genetic diversity and mitigate impacts of environmental stochasticity for target species. However, the genetic provenance of stock animals used in reintroductions can have lasting effects and needs careful consideration. Ocelots (Leopardus pardalis) are a target species for reintroduction in the United States, given that there are likely fewer than 100 individuals remaining in two isolated populations in South Texas. Reintroduction efforts have begun, with the official ground breaking of the ex-situ breeding center in 2024. To maximize the success of ex-situ breeding and reintroduction efforts, I: 1) assessed genetic diversity and inbreeding of wild ocelots and 2) analyzed genetic divergence between wild and zoo-sourced ocelots to inform the selection of ex-situ breeding candidates. Using whole genome sequencing, I found that wild ocelots had significantly lower nucleotide diversity (Ranch: 0.0017, Refuge: 0.0018, Generic:0.0032, Brazilian: 0.0033) and higher inbreeding (wild: 43.23-50.67% genome in run of homozygosity, zoo-based: 1.13-3.57% genome in run of homozygosity) than zoo-based ocelots. In addition, I identified evidence of dispersal (n=5) and gene flow (n=2 first-generation offspring) between the wild South Texas populations. These are the first dispersers documented between populations since at least 1991. The offspring of dispersers had higher genetic diversity than either parental population, which demonstrates how gene flow can ameliorate the loss of genetic diversity, even among inbred populations. I evaluated the potential of zoo-based stocks (Brazilian and Generic) for the ex-situ breeding in reference to genetic diversity as well as genetic distance and divergence from wild South Texas stocks. Brazilian ocelots had the highest genetic diversity, with > 32,000 private alleles, while Generic ocelots had > 14,000 private alleles, and were less genetically divergent from wild ocelots. Overall, zoo-based stocks had higher greater nucleotide diversity and fewer ROH than wild stocks. Either stock would be suitable for ex-situ breeding, but consideration of individual variation in the selection of founding individuals is necessary, as ROH ranged from 0% to > 15% of the genome. This research is the first to show gene flow between wild ocelot populations in the United States and adds to the growing literature on ex-situ breeding considerations to inform species reintroductions, ultimately providing critical information to support ocelot reintroduction and recovery
A correlational study of economically disadvantaged students and number of exlcusionary discipline referrals received in three similar South Texas school districts
No full textThe purpose of this quantitative, correlational study was to investigate the extent to which being labeled as an economically disadvantaged student contributed to the number of exclusionary discipline referrals in secondary schools belonging to three neighboring school districts in South Texas. The framework was based upon the Diamond et al. (2004) study which, like this research, was built on the idea that socioeconomic inequality is a key factor for disproportionality in student discipline. This study was conducted in South Texas with school discipline data being collected from three secondary campuses in the rural South Texas area. The three school campuses studied each have a population of approximately more than 60% of students on free and reduced lunch. Data for this research study was derived from student discipline reports and records provided by each school district through the Public Education Information Management System or PEIMS. The point-biserial application of Pearson (rpb) was used to compute the correlation between the variables.
The results of this study revealed that there was a positive, albeit weak correlation between a student’s socioeconomic status and their behavior at school, as evidenced through the number of exclusionary discipline referrals received. Though there was a correlation among a student’s socioeconomic status and exclusionary discipline referrals, educators must be careful to not assume that children living in poverty are ill-equipped to be successful in school. Given this knowledge and the findings of this study, administrators and teachers can communicate methods by which the school can create experiences and opportunities for this particular group of students. The findings provide prospects for additional exploration into why this population of students are more likely to receive exclusionary discipline sanctions
Analyzing the early age behavior of Continuously Reinforced Concrete Pavements (CRCP) under their environmental loading
No full textThis thesis investigates the behavior of Continuously Reinforced Concrete Pavements
(CRCP) with respect to material properties, environmental conditions, and longitudinal
reinforcement depths, focusing on their effects on stress distribution and horizontal cracking.
CRCPs are crucial for the durability of transportation infrastructure, requiring an in-depth
understanding of their performance under various conditions to ensure longevity and resilience.
An advanced analytical approach using ANSYS software was employed to model and
evaluate CRCP responses under one hundred forty-four different scenarios. Key factors analyzed
include aggregate characteristics, reinforcement positions, temperature variations, and moisture
content. The study also examines the impact of various longitudinal reinforcement depths and
configurations on stress distribution and the propensity for horizontal cracking within CRCPs.
The key findings include:
1. Temperature Variations: Larger temperature drops significantly increase Maximum
Normal Stresses, exacerbating the risk of horizontal cracking.
2. Material Properties: Higher modulus of elasticity and CoTE values lead to greater stress
levels and deformation.
3. Reinforcement Configuration: Mid-depth reinforcement results in lower stress
concentrations compared to top reinforcement.
4. Environmental Conditions: Increased drying shrinkage leads to higher stress and
deformation, highlighting the importance of moisture management in CRCP design.
The detailed stress analysis provides quantitative data for refining CRCP design
guidelines, optimizing reinforcement strategies, improving material selection, and adapting
designs for diverse environmental conditions. These insights contribute to the development of
more resilient and durable pavement structures
Fine scale habitat use and movement of ocelots and bobcats
No full textOcelots (Leopardus pardalis) are a medium-sized wild felid native to South Texas. Ocelots are a species heavily dependent on vegetation cover and in South Texas depend on the availability of dense, woody and shrub cover. As the availability of these habitat types has declined due to urbanization and agriculture, populations of ocelots have declined, leading to the species being listed as federally endangered in the United States. As such, understanding the movement and habitat selection of ocelots is paramount to conserving local populations. Ocelots in Texas share their environment with two other ecologically similar species, the bobcat (Lynx rufus) and the coyote (Canis latrans). Understanding mechanisms of coexistence is essential for managing a target species. Advances in monitoring technology have provided the ability to obtain reliable, high-frequency data on wildlife. We monitored 8 ocelots (Leopardus pardalis), 13 bobcats (Lynx rufus), and 5 coyotes (Canis latrans) on the East Foundation’s El Sauz Ranch and the Yturria San Francisco Ranch in South Texas, USA, which were fitted with GPS collars that collected locations every 30 minutes. We examined fine-scale habitat selection and movement of ocelots and examined differences between competitor species to examine coexistence within the carnivore community. We compared spatial and temporal differences associated with differing behaviors between species using hidden Markov models. We then examine individual and population level selection of vegetation structure using step selection functions. We identified selection of thermal refuge by ocelots and bobcats during extreme heat and cold to examine how abiotic factors influenced interspecific competition. We compared habitat selection between all three species at the 2nd and 3rd order and examined avoidance of competitor species by ocelots across scales. We observed evidence of behaviorally mediated coexistence through spatial and temporal partitioning wherein ocelots and bobcats were active at night and rested in dense cover during the day while coyotes were active during the day and rested in more open areas at night. We observed fine-scale habitat partitioning and differences in selection for upper and lower story vegetation within and across species. We identified dense shrub and forest cover as essential thermal refuge for ocelots and bobcats, and show how abiotic factors can act to influence interspecific competition through niche partitioning. We observed differences in avoidance of competitor species across species and scales by ocelots, wherein bobcats were not avoided at any scale while coyotes were avoided at the 3rd order but not the 2nd. We provide a more comprehensive analysis of habitat selection by ocelots than previously available and compare selection between sympatric ocelots and bobcats, identifying several mechanisms of coexistence within this carnivore community
Movie review with sentiment analysis and emotion detection
No full textContent users frequently consult review or survey sites regarding content ratings when determining which content to see next. Currently, content users determine which content to see by looking at the ratings and reading reviews on different platforms such as IMDB or Rotten Tomatoes. In this thesis, an alternate approach is explored in which reviewers' movie scores and reviews get evaluated for emotional content and collected to produce an emotion analysis for the content. Using that, a viewer can choose which content to watch next by exploring the emotion probability predictions with specific patterns that are appealing to that viewer’s interests. This research compares different methods of machine learning and deep learning for sentiment analysis and emotion detection of content reviews and surveys. Three different methods are compared in this work for sentiment analysis and emotion detection from user reviews and surveys. The three methods compared in this work are logistic regression, support vector machines, and recurrent neural networks. This work found that the accuracies for emotion detection with logistic regression, SVM, and RNN approaches was 77%, 78%, and 75%, respectively. The SVM method was observed to result in the most accurate emotion and sentiment detection from user reviews and surveys
A heuristic algorithm for the capacity-constrained multiple vehicle routing problem
No full textThe movement of goods is one of the important elements in the supply chain. As the supply chain industry has grown exponentially in the United States and other parts of the world over the years, effective transportation has been requested continuously. Because transportation cost accounts for a large part of the overall costs, minimizing transportation cost leads to a lower overall cost. One of the major transportation constraints for medium and large logistics companies is vehicle capacity. This research proposes a heuristic algorithm to determine the optimal routing policy for a capacitated multiple vehicle routing problem to minimize the total transportation costs. Although the exact algorithm provides the most accurate solution, its computational time is generally very long. Developing a heuristic algorithm is the most suitable approach to this kind of complex and large-scale problem because of its reduced computational time. The results of the proposed algorithm will be tested and compared with the outputs of other techniques
Indirect method of controlling thermal cracks in FRP reinforced concrete beams under elevated temperature
No full textDuring the past decades, there have been multiple interests in the use of Fiber Reinforced Polymers (FRPs) in construction. This is because of its unique characteristics, such as high strength to weight ratio when compared to steel, low modulus, and corrosion resistance. Despite these benefits, there has yet to be any work in literature to control cracking in FRP reinforced concrete beams at elevated temperatures. Therefore, this study aims to address the gap in the literature. A thermal crack width model using Frosch’s equation was developed and compared with a finite element model for various concrete covers. The error range produced by the model was found to be between 1.26% to 9.69% for Twelve models with differing concrete covers and stirrup spacing values. The finite element model demonstrated conservative results, likely due to the challenge of obtaining the maximum strain in concrete at the exact point of analysis. This thesis contributes to a better understanding of the behavior of FRP reinforced concrete beams under thermal loading. It has significant implications for future design and construction practices by providing a reliable thermal crack width model and supporting equations modified from Frosch’s equation