Texas A&M University-Kingsville: AKM Digital Repository
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1689 research outputs found
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Analysis of particle and reactor-scale transport-kinetic interactions CO2 methanation
No full textThe design of an externally cooled fixed-bed reactor for CO2 methanation has been performed using microscopic forms of reaction engineering models that account for both particle-scale and reactor-scale transport-kinetic interactions. The predictions of various multicomponent specie flux models were compared to analyze the transport-kinetics interactions for a spherical catalyst particle shape. Flux models that included Knudsen diffusion resulted in an increase in both the CO2 conversion and CH4 yield as the pore diameter was reduced from 40 nm to 10 nm. Both 1-dimensional (1-D) and 2-dimensional (2-D) models for different catalyst shapes were also simulated to quantify particle-scale performance for CO2 methanation. A spherical catalyst shape was shown to produce a higher CH4 average concentration, while a 4-hole cylindrical shape has the lowest diffusion limitation. An externally cooled 1-D heterogeneous fixed bed reactor was simulated using spherical catalyst pellets. The high exothermicity of the CO2 methanation reaction creates significant hot spot formation. In order to control the axial reactor temperature within a user-prescribed bound, the optimal catalyst loading profile was determined by using an energy conservation equation-based approach. It is shown that the reactor hot spot temperature can be controlled within a reasonable range
Thermal modeling and energy analysis of concentrated photovoltaic thermal system at different operating conditions
No full textConcentrated Photovoltaic Thermal (CPVT) system is a reliable solar energy system that utilizes sunlight of higher concentration on a photovoltaic cell to generate electricity that is superior to conventional solar systems due to fewer space requirements and high electrical and thermal efficiencies. The goal of this research is to use a CPVT system and test different operating conditions under which the system might work. This was achieved by exhibiting a contrast of electrical and thermal efficiencies when the velocity of water in the cooling channel was fixed while the amount of heat applied to the photovoltaic cells was varied and when the velocity of water in the cooling channel was varied while the amount of heat applied to the photovoltaic cells was fixed. Through mathematical modeling, that includes, thermal modeling along with energy and electrical analysis was carried out for the CPVT system. A three-dimensional finite element analysis (FEA) method was used to perform simulations to find the temperature of the photovoltaic cells and outlet water using Ansys Workbench (Fluent). The results from this research provide a useful path in improving the efficiency of the concentrated photovoltaic thermal system
The perceptions of early childhood teachers and the impact of STAAR on school readiness
No full textThis study investigated the perceptions of kindergarten teachers regarding their views on the impact of the State of Texas Assessments of Academic Readiness (STAAR) on readiness. Based on the review of the literature regarding child development and school readiness, input was sought from a sample of five kindergarten teachers in two neighboring counties who were interviewed for this basic qualitative study (Erlandson, Harris, Skipper, & Allen, 1993). Participants were asked to respond to a series of semi-structured questions about their teaching experiences, kindergarten expectations, and current climate of their teaching environments. Analysis of the responses demonstrated that expectations of the STAAR test has had an impact on kindergarten students. The results indicated that academic standards that were once assigned to upper grade levels are now being taught in kindergarten, which necessitates kindergartners possessing academic ability and higher-level language skills prior to the first day of school. Further research is needed to support the alignment of child development stages with school readiness.
Keywords: STAAR, kindergarten, developmental stages, school readiness, academic expectations, vocabular
Lime rock asphalt used as asphalt treated base
No full textAs the search for natural gas and oil continues in South Texas, the number of heavy axial load vehicles on the road has increased. More and more roads are affected by the pavement distress and civil engineers need to come up with a solution. The Texas Department of Transportation (TXDOT) must now come up with a design that is cost effective, durable, long lasting and most importantly, be able to withstand the increase in heavy axial loads. Different options that range from rigid to flexible, but cost and availability are always an issue. Limestone Rocks Asphalt (LRA) has been used in TXDOT for several years as a patching material. LRA is unique because it’s impregnated with naturally occurring asphalt and therefore minimal use of asphalt will be required. The objective of this research is to find an alternative to Cement Treated Bases, Lime Treated Bases. The results of this study validate that LRA can be used as Asphalt Treated Base alternative which could be more cost effective from other materials
Response of tanglehead to prescribed burning and cattle grazing
No full textTanglehead (Heteropogon contortus) is a grass native to south Texas but is now considered invasive, detrimental to cattle (Bos taurus) grazing and biodiversity on some native rangelands. The objectives of this study were to determine the effects of prescribed fire and cattle grazing on 1) the composition of a plant community dominated by tanglehead; and 2) cattle use of tanglehead-dominated areas treated with prescribed fire. The study was conducted in Jim Hogg County, Texas where patches of a tanglehead-dominated pasture were burned then grazed by free-ranging cattle. I tested the hypothesis that cattle would increase their grazing efforts on recently burned tanglehead, and the removal of tanglehead by cattle would increase the number of plant species on recently burned areas. My results indicate that the combination of grazing and burning is an effective tool to increase plant species richness and cattle grazing on tanglehead-dominated areas, and the beneficial effects of this treatment will persist for over a year. By using classified daily satellite imagery and GPS collars I also confirmed that cattle tend to avoid mature tanglehead plants in preference to other species, and prescribed fire increased the use of the burned areas by cattle
Impacts of agriculture on pronghorn in the Texas Panhandle
No full textNative pronghorn habitat across North America is being lost to agriculture and urban development at an alarming rate. Research is outdated or lacking on how these features impact pronghorn movements in Texas. I captured and collared 86 adult pronghorn in Dalhart and Pampa, Texas. I analyzed time based local convex hull home ranges and utilization distributions constructed using 431,176 GPS locations of pronghorn from 2017–2019. Roads, both paved and unpaved, were the greatest factors influencing home range establishment. Pronghorn inhabiting areas of high cultivation selected cultivated agriculture and areas of green, nutritious vegetation in rut and winter. Population level selection for a specific crop type was not detected, however, >50% of males and >64% of females utilized winter wheat. Depletion of water sources sustaining agriculture in the Texas Panhandle could lead to food availability issues for pronghorn in the future. While agriculture may temporarily sustain populations, it causes direct and indirect fragmentation and habitat loss across the landscape. When agricultural crops are lost from the landscape, populations of pronghorn will be left in a fragmented and nutritionally exhausted landscape. I recommend focusing policy on restoration and protection of native grasslands rather than temporary control of populations utilizing crops
Constructing 2 isoforms of hataxia-2 to gain an insight into its cell biological function using Drosophila melanogaster as a model
No full textSpinocerebellar ataxia type 2 (SCA2) is a member of a heterogenous group of neurogenerative disorders that cause a disruption in balance by affecting the cerebellar neurons. SCA2 is caused by an expansion of 34 or more CAG trinucleotide repeats, encoding a polyglutamine (polyQ) in the N-terminal region of ATXN2 gene. Ataxin-2 protein has a cytoplasmic location, which is essential for its pathogenesis through a gain of toxic mechanism that targets Purkinje cells in the cerebellum and promotes cell death. However, there has been a historical controversy about the cellular distribution of Ataxin-2. To investigate and understand the cell biological function and localization of Ataxin-2 in humans, two native isoforms of hAtaxin-2 is explored in transgenic constructs that will be investigated in Drosophila. Four versions were generated to be tested in Drosophila melanogaster: (1) A short version that naturally occurs without the poly-glutamine tract, with nuclear localization signaling (NLS) along with lexA::QFAD; (2) that same version without forced nuclear localization. (3) A version with the N-terminus containing 23 CAG repeats fused with NLS and lexA::QFAD. Finally, (4) the same without forced nuclear localization
TDDFT studies on sheet size-dependency of optoelectronic properties of 2D silicon doped with alkali metals
No full textSilicene, a two-dimensional (2D) silicon nanosheet, has gained immense interest due to potential applications, better compatibility, and expected integration with current silicon (Si) technology. This work explores the effects of silicene sheet size on its optoelectronic properties using Time-Dependent Density Functional Theory (TDDFT). Four structures of hydrogen-terminated silicene, Si13H22, Si19H30, Si54H74, and Si104H134 are investigated. It is observed that the structures have size tunable spectral response in the UV spectrum. The optimized sheets show a relatively smaller physical deformation compared to equivalent sized 2D Germanium sheets. IR spectra calculation of various bond vibrations show a good match with reported experimental results. The results show the potential for these 2D sheets to be effective optoelectronic materials in the visible spectrum, unlike bulk Si and Si nanowires. Furthermore, the effect of doping alkali metals (Li, Na and K) removing the H atoms in the silicene sheets were also investigated and their dipole moment and bond lengths are reported
Effect of dietary sulfur on digestion of feedstuffs and microbial populations in Dorper wethers
No full textThe potential of sulfur to increase digestibility and improve efficiency of production would benefit the food animal industry. The primary objective of the proposed study is to evaluate the effect of sulfur on in vitro true digestibility (IVTD) of various feedstuffs. A secondary objective is to utilize massively parallel sequencing to evaluate the effect of sulfur on the rumen microbial community. Dietary sulfur was added to a commercial feed ration and fed to individually housed Dorper wethers (n=10) daily. Upon completion of the trial, sheep were harvested and rumen fluid was collected for sequencing and evaluation of IVTD. Data were analyzed using the MIXED procedure of SAS 9.4 (SAS Inst. Inc., Cary, NC) when evaluating the effect of dietary sulfur on in vitro true digestibility. Massively parallel sequencing data were analyzed using QIIME scripts, using non-parametric ANOVA (Kruskal-Wallis). When evaluating the effects of dietary sulfur IVTD of various feedstuffs, a feedstuff effect was observed in roughages (P ≤ 0.01), concentrates (P ≤ 0.01), and roughages and concentrates combined (P ≤ 0.01). When evaluating the effects of varying levels of added dietary sulfur fed to Dorper wethers on IVTD, added sulfur had no effect (P = 0.16) on digestibility. Rumen fluid from sheep fed sulfur also had no effect (P = 0.81) on digestibility of feeds. When evaluating the effect of sulfur on microbial populations in Dorper wethers, Mollicutes RF39 (P = 0.01) and Ruminococcus albus (P = 0.01) decreased while Methanobrevribacter (P = 0.02) increased
Object detection and classification through a dashcam for an autonomous vehicle
No full textObject recognition and detection plays an important role in understanding the surrounding of an autonomous vehicle. In current systems, information from expensive sensors and cameras are used to create a model that will detect surrounding objects. But advancement in camera technologies can provide us huge sets of data through just a high definition camera. In this research, an object detection system based on a dash camera mounted in autonomous vehicles is proposed. The object detection algorithm proposed model is based on the Viola Jones algorithm and is compared to a convolution neural network approach. Based on the findings, the efficiency and accuracy of the proposed method to detect vehicles was found to be superior to the other neural network approaches. The proposed method used in this paper had an accuracy of 98% compared to 94% for the convolution neural network approach. The proposed method took 35 seconds on average as compared to several minutes for the convolution neural network to detect the objects in one image on the same system for training to testing. The proposed method recognizes the object in the image precisely and it takes less time than the other neural network-based algorithms. The proposed model is trained on low-quality images taken from a low-cost camera, which requires very low computing power, eliminating need for costly components. This low-cost implementation will allow existing vehicles to be fitted with autonomous object detection technology with just a dash camera