Texas A&M University-Kingsville: AKM Digital Repository
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Hydrologic and water quality evaluation and modeling of permeable pavement and recycled bioretention media in the semi-arid lower Rio Grande Valley of South Texas
No full textThe present research investigated two low impact development measures, permeable pavement and bioretention, to potentially mitigate non-point source pollution in the Lower Rio Grande Valley (LRGV) region of South Texas within the Arroyo Colorado watershed. In the first phase, hydrologic and water quality aspects of porous concrete and permeable interlocking concrete pavers (with and without gravel) were investigated as a surfacing material of permeable pavement, through a field-based study. A significant (p < 0.05) reduction in the runoff volume (98%), peak flow (85%), and suspended solids (80%) were observed from the porous concrete aggregate among all types. The computational model WinSLAMM was used to develop calibrated models (NSE ≥ 0.90, p < 0.05) of monitored pavements to predict runoff reduction for a wide range of rainfall magnitudes, sizes of the installation, and development sizes. Later, the research evaluated recycled concrete aggregate (RCA) as a filter media to analyze the fate of nitrate, orthophosphate, and humic acid through a bench-scale column investigation. Two other recycled materials- crushed glass and rice husks, and a layered media (LM) configuration of three materials were also investigated. HYDRUS-1D is a one-dimensional finite element solute transport and reaction model. This tool was used to simulate and investigate one-dimensional solute transport, adsorption in equilibrium, and reaction kinetics of pollutants in unsaturated media columns. Overall, RCA demonstrated an significantly (p < 0.05) increased orthophosphate removal (73-94%), perhaps due to the presence of Anorthite (a calcium-rich crystalline mineral) and its favorable surface textures to support surface precipitation reaction (kr,d = 0.108 min-1, kr,s = 3.45 min-1) and physisorption (Qmax = 186.9 mg/g) of the phosphate. HYDRUS-estimated results suggested that the thickness and saturated moisture content of the media might influence the removal of nutrients and humic acid. The RCA and LM were further investigated for nutrients and solids removal under intermittent and frequent flow operations with two feed concentrations. Our experimental results indicated increased nutrients and solids removal under frequent and intermittent operations, respectively. The removal of nitrite (67%) and nitrate (66%) was maximized under low feed frequent operations in the LM. Results also indicated that RCA alone was effective under high feed frequent operations in terms of orthophosphate removal (≤ 96%). Conversely, TSS removal was significantly (p < 0.05) higher in the LM column during initial intermittent operations. The findings from this research would contribute to meeting LRGVs regional water quality goals with innovative and sustainable permeable pavements and bioretention media design
Faculty knowledge and preparedness with ADA compliance and the relationship to student success in higher education
No full textHigher education instructional faculty have a multitude of job responsibilities other than classroom instruction. One of those responsibilities is the implementation of accommodations for students with disclosed disabilities. This quantitative study sought to determine if a
relationship exists between faculty members’ knowledge and preparedness with ADA compliance and student success. Individuals with Disabilities Education Act of 1990 (IDEA) emphasizes preparing a transition plan for special education students in grades P-12, therefore generating research on how instructional faculty can assist students with disabilities meet their educational goals post high school. This study conducted a non-experimental survey to gather data from higher education faculty members on their knowledge regarding the requirements of the Americans with Disabilities Act and their preparedness to implement accommodations. Pearson’ Correlation was conducted to show if faculty knowledge and preparedness in ADA compliance can be associated with student success. Based on the information gathered, data informed recommendations are made on the needs of faculty members in servicing all students. The results of this study revealed that there is no statistically significant correlation between higher education instructional faculty members’ knowledge and preparedness to implement
services to students with disabilities and success rates. Results will assist higher education faculty and administration with recommendations as to what may impact success of students with disabilities
System modeling of distributed generation with multiple renewable energy sources interconnection and power frequency fluctuation minimization
No full textRenewable energy penetration of the power grid has brought improvements in electrical power distribution reliability, by reducing the peak power requirements of the power grid. This has also led to an increase in grid power efficiency, while mitigating global warming and economic issues as many end-of-life fossil fuel power generation plants are being phased out and replaced by renewable energy power generation. Distributed renewable energy generation, also known as distributed generation (DG), implements small to large scale wind, solar, geothermal, and biomass power plants installed at the distribution level to offset the high demand of electric energy by consumers. Wind and solar power generation are the fastest growing principal renewable energy generation sources due to their structural flexibility, which makes it easier for installation, easy accessibility of renewable energy resources (i.e., wind and sunlight), less maintenance, and cost-effectiveness when implemented. Although renewable energy integration with the power grid has proven beneficial in terms of improved grid efficiency, increased system capacity, and reliability, their integration poses significant stability challenges to the grid due to the inherent intermittent nature of the renewable energy resources that affects voltage dynamics and power frequency. Secondly, constructing a DG system without conceptual modeling and planning can introduce grid capacity and energy flow issues. This research seeks to address issues related to voltage regulation, including plant stability and power frequency performance for renewable DG penetration with the power grid. The mathematical model for the system dynamics of a three-phase voltage source inverter-based DG connected to the grid will be implemented to determine voltage stability and power frequency performance using robust and adaptive control strategies. The research objectives are: 1) Model a typical distributed generation (DG) system connected to the power grid using system modeling language (SysML) through system modeling processes. Multiple DG (i.e., solar, wind, and biomass) connected to the power grid will be modeled at the system-of-system (SoS) level to describe the system component characteristics, system requirements, parameters, and functional allocation for the effective realization of the actual system design. 2) System-of-systems energy management for multiple DG connected to the power grid will be modeled and analyzed using SysML. An energy price cost optimization problem with energy from photovoltaic connected to the grid will be investigated in the MATLAB/Simulink environment 3) Electricity demand forecasting based on renewable energy data penetration will be analyzed for grid profile analysis. 4) A DG Inverter-based system is considered in this research to explore the system dynamics; controller design and evaluation of the simulation is done using MATLAB/Simulink. The dynamic model for the proposed DG inverter-based system was determined, and a robust and adaptive nonlinear control strategy was implemented to design controllers to meet performance and stability requirements for voltage regulation and power frequency fluctuation. The control design guarantees system robustness, self-regulation, and suppressing of disturbances coming from the inverter voltage and grid frequency. 5) An experimental laboratory setup consisting of DC voltage source and a single-phase microinverter from Texas Instrument will be used for further verification
Emergent bilinguals’ academic achievement in high-performing districts : does program type matter?
No full textThis study employs an exploratory descriptive quantitative statistics design. District-level results in the State of Texas Assessments of Academic Readiness (STAAR) are explored to describe the achievement gaps that exist in districts implementing Transitional Bilingual Education (TBE) programs and districts implementing Dual Language (DL) programs. The study explores emergent bilingual (EB) students’ mean STAAR performance in high-performing districts implementing TBE by disaggregating EB students’ performance data from the districts’ performance. High-performing districts are those that received an ‘A’ rating in the 2018-2019 A-F Accountability System in Texas. EB students’ performance data is aggregated across districts and across regions to describe the achievement gaps that exist despite the high-performing ‘A’ rating. The study uses the districts’ and EB students’ mean STAAR performance for 3rd – 5th grade in Reading Language Arts (RLA), Math, and Science as recorded in the publicly accessible Texas Academic Performance Reports (TAPR).
The following questions guide the study: (1) What is the STAAR achievement gap between the districts’ mean performance and the mean performance of EB students when they participate in high-performing districts with TBE programs?; (2) What is the STAAR achievement gap between the districts’ mean performance and the mean performance of EBstudents when they participate in districts with DL programs, regardless of accountability rating?; and (3) How does the STAAR achievement gap of the districts’ mean performance and the mean performance of EB students in high-performing districts with TBE programs compare to the STAAR achievement gap of the districts’ mean performance and the mean performance of EBs in DL programs?
This study uses achievement gap metrics (Ho & Reardon, 2012; Rodriguez et al., 2016; Stevens, 2017) to analyze the data found in the TAPR and describe the achievement gaps that exist between districts’ STAAR mean performance of EB students from ‘A’ rated districts implementing TBE and the districts’ mean performance of EB students from DL programs.
The findings, presented at the state, region, and district level, reveal a large achievement gap between the districts’ mean performance and the EB students mean performance in ‘A’ rated districts implementing TBE programs. In comparison, the findings show a smaller achievement gap between the districts’ mean performance and the EBs mean performance in districts implementing DL programs, regardless of their district accountability rating. A higher percentage of districts implementing DL programs show that EBs outperform the districts’ mean performance when compared to ‘A’ rated districts implementing TBE
Automated inspection system for visual defect detection for PV plants
No full textOf late, there is a significant increase in the installation of photovoltaic (PV) plants. The essential modules to ensure the effectual and dependable operation of extensive photovoltaic plants are condition monitoring and fault diagnosis. Since the last decade, many PV systems have been installed in the field and they often exhibit a range of failures compromising the performance and energy generation of the power plants. Operation and maintenance are vital factors for PV plant examination and control exercises, which as of now are very difficult to perform because of manual and dispersive procedures. Utilization of unmanned aerial technologies can exploit the plant examination and control of sustainable power sources. In this thesis, the PV fields are examined
by visual imaging and image processing techniques were utilized to highlight defects. In addition, the image-processing algorithm developed in this research can find visual defects from an entire PV field to facilitate the decision-making results for the detection of defects. It has been implemented in state-of-the-art operation and maintenance practices for PV plants
Developing umanned aerial vehicle approaches for range and wildlife habitat studies
No full textThe use of unmanned aerial vehicles (UAVs) has exponentially increased in recent years for monitoring and managing rangelands. The aim of my project was to develop approaches and applications useful for assessment of rangeland woody cover encroachment and forage mass estimation. The specific objectives of my research were to (1) integrate UAV and satellite imagery
to quantify the amount and spatial distribution of honey mesquite (Prosopis glandulosa) in rangelands and (2) develop broad scale approaches to quantify forage mass in rangelands. For the first objective, I established study sites in three different ecoregions where I used field methods to record canopy heights and then flew a UAV over the study sites at two altitudes, 50 meters above
ground level (AGL) and 100 meters AGL. I used linear regression to relate field canopy heights to UAV derived canopy heights (r2 = 0.59 to 0.95). I then used honey mesquite locations and height attributes from UAV outputs and satellite imagery to quantify spatial distribution of honey mesquite using machine learning techniques (overall accuracy > 80%). To accomplish the second
objective, I used a UAV to create orthoimagery, digital surface models, and digital terrain models at 50 and 100 meters AGL within the South Texas Plains ecoregion. I performed six forage mass sampling techniques that included field based and UAV based methods. Linear regression analysis was used to evaluate relationships between UAV derived vegetation volume for each flight altitude and the forage mass derived from each forge mass sampling method (r2 = 0.35 to 0.85). This
research showed the capabilities and applications of UAVs in rangeland research and management. The use of UAVs can be used to quantify honey mesquite cover over large areas using machine learning, and can be used to estimate forage mass on rangelands in large-scale pastures
Field deployable loop mediated isothermal amplification (lamp) assay for the detection of 'Candidatus liberibacter asiaticus' in citrus
No full textHuanglongbing (HLB, citrus greening disease) is a destructive disease that undermines the production of citrus around the world. The presumed causal organism, ‘Candidatus Liberibacter asiaticus’ (CLas) is a non-culturable, fastidious and phloem limited α-proteobacterium. Pre-symptomatic field-based CLas detection techniques would empower the growers to implement better HLB management strategies for mitigating the spread of the disease. The current study focused on the development of a field deployable Loop Mediated Isothermal Amplification (LAMP) method for CLas detection. We designed primers for the LAMP assay based on the CLas five copy gene, nrdB, encoding the β-subunit of ribonucleotide reductase (RNR), an enzyme critical for multiplication of the bacteria. The assay was optimized for CLas detection from leaf, bark, root and psyllid samples. The estimated detection limit of the LAMP assay was ~ 2.2 × 103 (~ 3.1 Log10 copy number) copies of target molecule. The observed sensitivity of the assay using field samples was slightly lower than qPCR-based assay as the LAMP assay produced inconsistent results for the samples with cycle threshold (Ct) greater than 30 (i.e. < ~103 copies of target molecule). However, the LAMP assay has 98.1% accuracy for samples with qPCR Ct values below 30. The assay was evaluated with crude DNA extracts from plant and psyllids using a portable device. The psyllid crude extracts were suitable and can be used for CLas detection using LAMP assay in field conditions
Improving the hydrophobicity of polymers through surface texturing
No full textImproving the hydrophobic property of polymers is essential considering the wide usage of polymers in various applications, including biomedical applications, and their tendency to degrade with long-term exposure to moisture environments. Several surface modification techniques have been developed over the years to improve the hydrophobic property of polymers. However, their influence on enhancing the hydrophobicity and long-term mechanical performance is yet to be fully understood. Although surface modification such as texturing may improve hydrophobicity, these surfaces tend to have low wear and abrasion resistance, which can deteriorate the long-term mechanical performance of polymers used in various prosthesis applications.
This research employs surface texturing as the surface modification technique to study the effect of surface modification on hydrophobic property of polymers. Theoretical study is conducted to investigate the feasibility of introducing surface textures on the polymers. Square and cylindrical surface textures, both protrusion and cavity, with variation in texture dimension are introduced on the surfaces of two model polymers, Ultrahigh Molecular Weight Polyethylene (UHMWPE) and High Density Polyethylene (HDPE); using a combination of laser engraving and hot pressing techniques. The surface textures are analyzed using a digital microscope and the hydrophobicity of polymer surfaces is measured using a custom-built water contact angle measurement setup. The results show that introduction of surface textures significantly improve the hydrophobicity of UHMWPE and HDPE. However, the relationship between texture type and dimension, and improvement in hydrophobicity is not straightforward. The study provides useful guidelines on improving the hydrophobic property of polymers
System identification for a RC helicopter
No full textUnmanned Aerial Vehicles (UAV) have been gaining popularity in recent years due to their versatility and ease of use in all walks of life like civilian use, military and industrial survey, disaster response and relief. This thesis explores the process of identifying the parameters of an RC Helicopter using system identification methods which helps us convert it into an autonomous UAV. We will be using X-Plane software to simulate the responses to the input for obtaining the basic system response which will be used for parameter identification of the system. The identified parameters will be used to test the real-world efficiency and accuracy of the simulation and be improved upon to get real-world parameters. The following pages contain an overview of the system identification concepts and basics of dynamics of a helicopter to give the reader a basic idea of the problem and various approaches will be expanded upon. An introduction to RC helicopters is also presented to educate the reader about the different types of helicopters, how lift is produced, and the type of stabilizers commonly used. The paper also aims to estimate the system parameters of a Bell-Hiller stabilized helicopter and a more modern flybarless helicopter
Northern bobwhite abundance in relation to cattle grazing in South Texas|
No full textRange management practices to improve habitat for wildlife often include reducing brush and increasing herbaceous plants. This coupled with lack of cattle grazing or low stocking rates, can lead to dense stands of dominant grasses, such as four-flower trichloris (Trichloris pluriflora). Monocultures like this create dense unsuitable vegetation for northern bobwhite (Colinus virginianus), while reducing plant species diversity, and altering ecosystem functions. The objective of this study was to evaluate the effects of a proper cattle grazing regime to improve bobwhite habitat. I hypothesized that (1) plant species richness will be greater in the grazing treatment, (2) cattle grazing will reduce the cover of trichloris, and (3) the grazing treatment will contain more bobwhites than the control. This study was conducted in Duval County, Texas, across two pastures totaling 2,500 ha. One pasture served as the control (1,337 ha) while the other was grazed (1,109 ha) to maintain a stubble height between 30 to 40 centimeters. I placed 10 grazing exclosures as well as 10 (25 meter) transects within each treatment to determine botanical composition, cover, and utilization. I used double sampling to determine forage standing crop. Plant species richness, total ground cover, forage standing crop, and forage utilization were measured. I also completed aerial surveys to estimate bobwhite densities. Plant species richness at the end of the study was higher in the control (4.1 species per transect) than the grazing (3.4 species per transect) treatment. Bare ground was greater in the grazing (20%) treatment as compared to the control (10%), as was litter in the grazing (25%) compared to the control (7%). At the end of study trichloris cover was greater in the control (72%) treatment as compared to the grazing (38%) showing the impact of cattle grazing. In 2020 I recorded bobwhite densities of 0.91 ± 0.2 bobwhites/ha in the grazing treatment and 0.56 ± 0.11 bobwhites/ha in the control. In 2021 I recorded bobwhite densities of 2.04 ± 0.48 bobwhites/ha in the grazing treatment and 1.63 ± 0.42 bobwhites/ha in the control. These results show how cattle grazing can be used as an effective management tool to improve habitat for bobwhites in South Texas and also the compatibility of cattle ranching with quail management