Texas A&M University-Kingsville: AKM Digital Repository
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Statistical and experimental analysis of the impact of atmospheric conditions on the efficiency of photovoltaic cells
No full textThe use of photovoltaic (PV) cells has proven to be one of the most practical, sustainable and ecofriendly ways of harnessing solar energy. However, these cells typically operate at efficiencies lower than what is ideally desired. This study will look at how PV cell efficiency can be improved upon, by finding the relation between efficiency and existing atmospheric conditions. We evaluate the simultaneous effect of four atmospheric factors, temperature, humidity, wind velocity and solar irradiance on PV cell efficiency through an experiment to measure the power output from a Renogy type RNG-30D monocrystalline PV module at the Texas A&M University-Kingsville. With experimental results and gathered data on the four atmospheric factors, a multiple regression analysis is used to develop a mathematical model that can be applied to calculate the instantaneous efficiency of a PV cell or system within the south Texas region. The current model shows higher accuracy when compared to a similar model proposed in previous research by comparing the mean absolute deviations and the mean squared errors of both models in relation to actual PV cell efficiency.
Keywords: Photovoltaic cell; solar energy; PV module efficienc
Design and testing of robotic units for rapid duplication and collaborative missions
No full textSwarm robots are usually based on duplicates of one unit robotic system that can communicate and collaborate to develop and accomplish tasks beyond the capabilities of the unit robot. The idea of a robotic swarm is to use as many robots as necessary to accomplish a task. This type of robotic systems is very helpful in many tasks and missions such as rescue within a cave, where entry is tight and allows only limited size robots, but the task inside the cave requires bigger and stronger machines. However, there are still multiple challenges facing the realization of these robotic systems such as time and manufacturing capabilities as well as computational capabilities to allow a sophisticated decision making process on site. Considering the recent advances in additive manufacturing or 3D printing, as well as the parallel advances in mechatronics, a superior process of producing swarm robots, in terms of efficiency and economy is proposed. The new system allows rapid manufacturing, assembly, and duplication of the unit robot, with a reasonable controller, and with the ability to reproduce numbers of units based on mission requirements, shifting some of the complex decision making process to the operator through a compromise between capabilities, production efficiency, and cost. Addition of a new robot or changing a task directive to the system would be as easy as printing, assembling, and adding modified algorithms to the new unit which will join the swarm and redirect the task. Results of this work include building and testing a unit robot with duplicates to demonstrate the proposed ideas
On improving randomized response techniques
No full textIn this thesis, we have introduced three new randomized response techniques. The proposed new techniques include: making use of a zero-truncated binomial distribution as a randomization device, an improvement on Warner’s model making use of a mixture of binomial and negative binomial distributions as a randomization device, and a similar technique for an improvement to Kuk’s model. The proposed models have been presented along with the resultant estimators. The percent relative efficiency and relative protection of respondents have been investigated with respect to their competitors
Acid gas control using hollow fiber membrane contactor: experimental and modeling study
No full textMembrane gas separation is a reliable alternative to traditional acid gas absorption techniques using direct contact of gas stream and scrubbing solvent without dispersion of one phase in another. The success of this technology is highly dependent on the types of membranes used in the gas-liquid contactor process. Microporous hollow fiber membranes act as the barrier between the gas and liquid phases and prevent the limitations caused by channeling, foaming, and flooding. Additionally, a high surface area to volume ratio of the membrane module can provide a substantial saving on space and weight requirements.
This dissertation investigated the potential of using commercially available hydrophobic PTFE hollow fiber membranes for acid gas control applications, in particular separation of CO2 from a CO2/CH4 gas mixture as well as removal of CO2 and NO2 from simulated flue gas streams. A gas-liquid membrane contacting apparatus was constructed and comprehensive experimental studies were performed to determine the gas absorption performance of the membrane system. Deionized-water and aqueous solutions of sodium hydroxide (NaOH), monoethanolamine (MEA), diethanolamine (DEA) and triethylamine (TEA) were employed as the absorbents. Operating parameters such as: gas and liquid cross flow velocities, feed gas concentration, temperature, nature of absorbent, scrubbing solvent concentration, packing density, module configuration, flow pattern, and long-term performance of modules were systematically evaluated in order to better understand the overall performance of the membrane system.
Results indicated that acidic gases (CO2 and NO2) absorption performance of the membrane system enhanced with increasing the liquid phase velocity, decreasing the gas phase velocity, and using chemical scrubbing absorbents. For the physical absorbent, the CO2 separation efficiency decreased with increasing the temperature, whereas increasing the temperature was in favor of system performance when using chemical absorbents. Moreover, it was shown the sodium hydroxide to be a superior absorbent as compared to alkanolamine solutions for the co-capture of CO2 and NO2 species. It was observed that low concentrations of NO2 in the feed gas had a minimal impact on the decarbonization of gas-liquid membrane contacting system. On the other hand, the module with smaller size hollow fibers showed the best performance for separation of acid gas compounds (CO2 and NO2) from the gas mixture. The long-term performance of the membrane system was also evaluated by running the simultaneous gas removal experiments over a 24-h period. The consistency of the absorption efficiency results confirmed the potential of using PTFE membrane system for the simultaneous absorption of CO2 and NO2 gases.
A comprehensive two-dimensional mass-transfer simulation model was developed to evaluate the separation process of CO2 from CO2/CH4 gas mixture using computational fluid dynamics (CFD). The governing mass transfer equations for all the three compartments of the membrane system (i.e. lumen-side, membrane, and shell-side) were solved using COMSOL Multiphysics. Convection and diffusion flux vectors and concentration gradient of CO2 species in the radial and axial directions of the membrane system were investigated. The simulation results reveal that increasing the absorbent velocity improved the CO2 separation performance of the membrane module, while increasing the gas mixture velocity deteriorated the CO2 removal of the system. The impact of hollow fibers geometry on the removal of CO2 from the gas mixture was investigated and the results indicate that hollow fibers with smaller inner diameters showed a superior CO2 removal in the membrane system. Furthermore, the predictions for the CO2 separation performance of the modules exhibited a good agreement with the experimental data under various ratios of gas to liquid volumetric flow rate
The influence of Chinese parents' ethic identity on their children's Chinese heritage language maintenance
No full textChinese population in the United States is increasing, as well as China’s international scientific, economic and political influences. Therefore, learning the Chinese heritage language (CHL) has become more important for Chinese immigrant families. The purpose of this quantitative study is to explore the impact of Chinese parent’s ethnic identity and attitudes on their children’s CHL maintenance. The parents’ ethnic identity would be the motivation for them to guide their children in childhood age to learn CHL. Parents can decide the family language policy (FLP). Parents with stronger Chinese ethnic identity may tend to choose Chinese as a home language, and children are exposed in the family environment with Chinese language daily, so consequently children’s Chinese will be proficient. A quantitative cross-sectional survey approach was used in this study to observe and collect concurrent data to analyze the relationship among variables of parents’ ethnic identity, FLP, parents’ CHL proficiency and their children’s CHL proficiency. This study utilized purposive sampling and surveyed from three Chinese schools, where two are located in Dallas and one in Houston, Texas, respectively. The participants of this study were the Chinese parents with children, ages between from 5 to 18 years old. An online survey (i.e., web-page questionnaire) was conducted (n=108) based on Phinney’s (1992) MEIM-R and other additional questions are offered. All parents of students in the three Chinese schools received an email of the SurveyMonkey link to the online survey from principal. In the three Chinese schools, there are a total of 319 students, whose ages range from 5 to 18 years old. Both parents can respond to the survey separately, and it is voluntary. There was a total of 108 viable surveys completed by parents. The data was then downloaded from Survey Monkey to Microsoft Excel. Bivariate correlation was used to analyze the relationship between each set of variables. The statistical results show that parents’ ethnic identity is positively correlated to children’s CHL proficiency (r =.31), and also positively correlated to FLP (r =.33). Both correlations were of medium positive strength. FLP is medium correlated to children’s CHL proficiency (r =.31). Parents’ CHL proficiency is medium correlated to children’s CHL orality skills, but small correlated with children’s CHL literacy skills. Children’s CHL literacy skills are related with weekend/after-school Chinese schools. The findings of three research questions, limitations, contributions and directions for future research are all addressed in the study
Managing cowherd dynamics in common-pool forage resource system dynamics application to small-holder herding in semi-arid Nigerian uplands
No full textCommon pool resource systems are defined as those systems where it is difficult to prevent prospective beneficiaries from receiving profits from use or harvest of commonly shared resource. Also referred to as common property systems, continual resource utilization commonly leads to over-use and degradation of the resource, which erodes economic gains from resource use over time (a behavior known as “tragedy of the commons”). Nigerian upland nomadic grazing systems pose a great challenge to the government and agrarian communities due to the prevailing management practice of open-access grazing by cattle. Animal additions done by herders to increase their net worth causes severe rangeland degradation and depleted common-pool forage resources. This situation has resulted in serious conflict, crop destruction, and loss of life, leading to increased social, economic and political tension. We modeled the cowherd dynamics in common-pool resource forage systems in Nigerian uplands to understand degradation dynamics and evaluated a series of calibration and what-if scenarios with the objective to understand the degradation dynamics and identify leverage points within the system to reduce degradation caused by overgrazing and ensure a sustainable livestock production system. Calibration test results reflected the dynamics of the problem while the three what-if scenarios (i.e., crop restriction, crop marketing and increased labor cost) resulted in only partial solutions and were very short-term and limited in geographic scope. An effective sustainable solution should be a combination of different measures because the impact of one scenario alone cannot effectively resolve Nigerian upland common-pool resource problems.
Understanding the forage systems via education of managers (herders) on the importance of carrying capacity and stocking rate, an agreement or consensus by herders to cooperate and operate within the sustainable productivity of forage resources through a change of socio-economic values and an enforcement of the policies and regulations already in place are the leverage point that can change the degradation trend in the region. The system dynamics model can be used to test the impact of various management decisions on Nigerian grazing lands. The manipulation of these factors will allow management to evaluate long-term effects of their decisions.
Keywords: Tragedy of the commons, Resource degradation, Nomadic herdsmen, Common-pool resource, Nigeria, Cattl
Design optimisation of a composite overwrapped pressure vessel through finite elemment analysis
No full textComposite overwrapped pressure vessels (COPVs) are presently utilized at National Aeronautics & Space Administration and other agencies to contain high-pressure fluids in propulsion. These COPV’s are used in space shuttles, space stations, aircraft technology, etc. These COPVs have a huge advantage in all kinds of metal vessels; however, when contrasted with every single metal vessel, COPVs require special design criteria, assembling, and test prerequisites. Therefore, design optimization of a filament wound pressure vessel is the main goal of this thesis. Finite element analysis is done on the polymer-lined composite overwrapped pressure vessel (type IV COPV) by numerical methods using Abaqus Wound Composite Modeler to improve the design. In this thesis, change in layer quantities and the winding angle are considered to find out the burst pressure for optimal design parameters of type IV COPV. Tsai Wu, Tsai Hill, maximum strain, maximum stress failure criteria are considered to figure out the burst pressure of the type IV COPV. Numerical simulation results were also compared with the experimental result to validate the numerical results
Comparing fog based smart parking system to cloud based smart parking system
No full textSmart parking system is gaining more attention now days with the increase in population in the busiest cities. Applications implemented using cloud computing are worth noting these days. However, when implementing apps that require immediate response with less latency and transmitting huge data back and forth to cloud would affect performance of an application. To trounce this barrier, fog computing concept has been proposed. The main reason for bringing down the fog computing concept into existence is due to the need of increased scalability and real time response.
This research is inspired from the college students and staff looking for a parking spot in the busiest times for hours together waiting to park their vehicle spending their time and fuel. The research mainly focuses on calibrating applications impact of managing resources in cost, power consumption, network traffic and transmission delays. Evaluation platforms named iFogSim [13] and CloudSim [12] are used to produce and compare results more repeatedly. The algorithm proposed in iFogSim addresses most serious problem in resource management methods as to where application modules are pushed close to end devices for maximizing throughput and minimizing transmission delays. The SPS application is developed and deployed in the fog environment mainly based on DDF-distributed data flow model [16]. We found our fog based smart parking system performed better in terms of energy consumption and network latencies
Investigating the context effects of expanded hexanucleotide repeats in fly model of human SCA 36
No full text(Spinocerebellar Ataxia 36) SCA36 is a neurodegenerative disorder that is caused by nucleotide
repeat expansions of GGCCTG in NOP56 gene. NOP56, also known as Nucleolar protein 56, is a component of ribonucleic protein complex that is involved in ribosomal biogenesis. The hexanucleotide repeat expansion mutation disease in the first intronic region of NOP56 gene causes SCA36 that mainly affects the cerebellum, which coordinates voluntary movements such as balance, speech and coordination. Cerebellum damage leads to issues with gait and dexterity known as ataxia. In order to investigate these nucleotide repeat expansions in various contexts, we generated expanded repeat-related constructs for SCA36 using the vectors pUAST and pUASTattB. Transgenic flies made from these vectors and the transgenic flies with the expanded repeats were crossed with specific drivers for gene expression and nervous system-associated phenotypic analysis. Generation of these flies allowed us to analyze whether these expanded repeats have intrinsic toxicity and if their toxicity can be modulated
Quail and rain: does management matter?
No full textRainfall is a strong driver of quail populations on southwestern rangelands and may account for a large portion (70–90%) of the variability in regional quail production and abundance. Landowners have attempted to moderate these boom-and-bust fluctuations via management, but presently it is unknown whether quail management indeed can increase or stabilize northern bobwhite (Colinus virginianus) populations on semi-arid rangelands characterized by erratic rainfall. The objective of my research was to evaluate the efficacy of bobwhite management at mitigating the effects of unpredictable rainfall on semi-arid rangelands. This study was conducted in the Rio Grande Plains (n = 6 ranches; ≈20,000 ha total) and Rolling Plains (n = 4 ranches; ≈15,000 ha total) of Texas. I estimated quail density on each ranch during a 5-year period (December 2014–2018) using helicopter surveys within a distance-sampling framework and obtained annual rainfall data from a Parameter-elevation Regressions on Independent Slopes Model (PRISM). I also quantified intensity of quail management via landowner questionnaires to categorize ranches into 3 relative categories of management intensity: low, medium, or high. In the Rio Grande Plains, mean bobwhite density pooled over the 5-yr period was numerically greater on ranches with high-intensity management (1.78 ± 0.45 bobwhites/ha; mean ± SE) than low-intensity management (1.53 ± 0.36 bobwhites/ha). However, variation in bobwhite density among years was high for both high-intensity management (CV: 57%) and low intensity management ranches (CV: 52%). Similarly, mean bobwhite density in the Rolling Plains pooled over the 5-yr period was numerically greater in ranches with highintensity management (1.59 ± 0.60 bobwhites/ha) than low-intensity management (0.85 ± 0.29 bobwhites/ha) and also exhibited moderate-to-high variation within management levels (CV:75% vs. 67%, respectively). These results suggest that management may increase quail density beyond that of less managed properties but may not completely eliminate the inter-annual fluctuations