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High-Temperature Ignition of HTPB-Based Mixtures in a Shock Tube
No full textHydroxyl-terminated polybutadiene (HTPB) is a molecule of continued interest within the aerospace community due to its excellent mechanical characteristics and combustibility as a rocket propellant ingredient. Recent developments in the defense and space industry such as the development of solid-fuel ramjets and solid rocket propellants depend on the characterization of HTPB as a fuel. However, much of the transport and thermodynamic data available for HTPB are relatively unknown due to the pyrolysis of HTPB to ethylene and butadiene occurring near the vaporization temperature of HTPB. The time scale of this pyrolysis is on the order of seconds and, therefore, a characterization of HTPB using timescales under one second is necessary. To achieve the sub-second characterization, the High-Pressure Shock Tube (HPST) at the TEES Turbomachinery Laboratory was utilized. A recent development for the HPST is the endwall injector system which utilizes the increase in temperature and pressure of the incident wave of the shock tube to vaporize the liquid fuel prior to the arrival of the post-reflected-shock conditions. The fuel is placed into the barrel of the injector, and the injector is actuated when the incident shock wave arrives at the location of a pressure transducer 2 m upstream from the endwall. The injector subsequently opens and allows 40 psia of air to blow through the fuel meniscus, sending it into the shock tube where it vaporizes upon interacting with the hot gas behind the incident wave. This thesis utilized the endwall injector system to test HTPB in sub-second time frames and record combustion at 2.5- and 4.25-atm conditions over a temperature range of 1230 to 1400 K. Additionally, in-situ additives were synthesized in the HTPB by collaborators at the University of Central Florida to produce HTPB-based mixtures without affecting the mechanical behavior of the fuel. This thesis studied a titania-infused HTPB mixture at a pressure of 4.25 atm and a temperature range of 1230 to 1400 K. Following the experiments of the HTPB based mixtures is a brief overview of the chemical kinetics data currently available on HTPB and current issues in modeling the molecule
International Trade Impact on Milk Product Market in the U.S. and LCA with Economic Analysis on Converting Lignin Waste to Sustainable Products
No full textThis dissertation investigates some economic issues regarding international trade and the production of byproducts in lignocellulosic ethanol production. This work is reported in three essays.
The first essay addresses how recent expansions in international trade affect Class I spatial milk price differentials in the U.S. Five international trading scenarios were simulated using a milk sector movement and processing model. The results reveal notable regional differences in the spatial characteristics of farm-level raw milk prices. We find the greatest effects are in the Eastern U.S. where we see significantly higher prices. We also see domestic milk price disparities, in areas like Idaho and New Mexico. Furthermore, the influence of international trade is clearly seen in prices of U.S. milk products that are exported or imported, especially for the products like Cheddar Cheese and Butter. The study emphasizes the need for a possible update in spatial milk price differentials considering the growing impacts of a globally interconnected market.
The second essay examines the net greenhouse gas emissions and market penetration implications of using the lignin byproduct from a lignocellulosic biorefinery to make carbon fiber. The results show that using lignin as a precursor for producing carbon fiber leads to a reduction in CO2 emissions compared to the conventional process of producing carbon fiber. We also analyzed the price and size of the market if the lignin-based carbon fiber was entered into existing carbon fiber markets under various elasticities. Here we found large scale production would lead to substantial carbon fiber price declines.
The third essay examines alternative choices for lignin utilization across a set of alternative downstream products. Namely, lignin can be used to make carbon fiber, asphalt binder modifier, PHA, and biodiesel lipids, when this is done our analysis finds a number of substantial economic and environmental benefits, most notably in reducing CO2 emissions. Market analysis under various scenarios, including the consideration of carbon emission prices, indicates that the optimal market entry of these products depends on production costs and carbon pricing. The findings suggest a strategic approach to lignin utilization, where prioritizing lignin-based carbon fiber production and adjusting outputs based on carbon emission costs can lead to maximum profitability while contributing positively to environmental sustainability
Sheep as a Potential Tool for In-Season Cotton Weed Management
No full textIncreased reliance on herbicides in crop production has led to many weed species becoming
resistant to multiple herbicide modes of action. Sheep herbivory may be a viable alternative
weed control method, as sheep have the potential to preferentially graze weeds and be averse to
eating the cotton plant due to the presence and concentration of gossypol. Common weeds such
as Palmer amaranth and field bindweed are major competitors with cotton plants in western
Texas but are also palatable to sheep. Field research on the integration of sheep into cotton
systems was performed at the Texas AgriLife extension and research center in San Angelo,
Texas during the 2022 and 2023 seasons. Treatments included three different cotton growth
stages to initiate grazing (4-leaf, 8-leaf, and mid-bloom) and three different levels of grazing
intensity based on weed removal (approximately 70%, 90%, and 100%) with presumably greater
cotton damage with increasing intensity. Treatment effects were quantified through monitoring
sheep grazing activity, assessments of weed biomass removal, cotton damage, and cotton yield.
During the 4-leaf, 8-leaf, and mid-bloom initiation for both years, sheep spent 87%, 86%, and
93% of feeding time, respectively, grazing on weeds rather than cotton. Final cotton biomass was
not influenced by year, intensity, or timing of treatments. Final weed biomass was affected by
year (P > 0.069) and timing (P > 0.036). The year 2022 had less final weed biomass than 2023
and grazing initiated at the 4-leaf stage resulted in greater weed biomass at the end of the
growing season when compared to grazing initiated at the 8-leaf stage. This trial emphasizes the
challenge of extrapolating small-scale findings to field conditions, where sheep grazing may
occur at different times. While small-plot research is valuable, its limitations highlight the need
for field-scale observations. Integrating sheep grazing into production systems shows promise for
farmers seeking reduced herbicide/organic management, but further refinement and consideration of economic impacts are necessary. Future research may assess grazing preferences relative to sheep age and breed to provide greater insight into integrated crop-livestock management practices
Improving Maize (Zea mays) Production: Assessing Impacts of Seed Cleaning, Treatment, and Novel White Sub-Tropical Inbred Varieties
No full textMaize is an important crop in the U.S. and globally and grain yield continues to increase from both agronomic and genetic technologies. Farmer���s successful crop establishment of maize has relied on treated and cleaned seed to reach plant population targets of healthy plants. The purpose of the first study was to determine the effects that cleaning and treating seed had on both the plant population and yield of a crop in small plots for a breeding program. Ten diverse experimental maize cultivars were chosen based on seed availability and subject to different combinations of cleaning and treating. The cultivars were tested across two years (2021 and 2022) and multiple environments. A reengineered Mater Continuous Seed Blower was used to clean the seed. Cruiser 5FS and Maxim 4FS were blended following recommendations and used as a seed treatment. Overall, the results of this experiment showed a positive correlation between cleaning and treating seeds and an increase in yield and plant population. The results help to reinforce the use of cleaning and treating techniques in seed preparation for small plot research.
The second study involved preparing a release of novel white inbred lines for white maize hybrids. The varieties proposed for release include Tx131, Tx133, Tx134, Tx148, Tx149, Tx150, Tx160 and Tx161. All inbreds listed are derived from white sub-tropical germplasm and can improve yield and genetic diversity white maize in the U.S. Current white maize varieties are limited, and this release will increase the genetic diversity providing farmers with more options for planting. These lines were crossed with a variety of commercial and within Texas A&M program testers, and resulting hybrids were grown at multiple locations over several years. Hybrids from each line produced yields that met or exceeded those of current commercial hybrids
Improving the Sensitivity of the Search for New Resonances in the X->HH->bbWW Channel at the LHC with the CMS Detector
No full textThe Standard Model (SM) of particle physics successfully describes fundamental particles and three out of four fundamental interactions. However, it fails to incorporate the fourth fundamental interaction, gravity, and cannot explain observed phenomena like matter-antimatter asymmetry. These limitations suggest new physics beyond the SM, possibly probed via Higgs boson pair (HH) production at the CERN Large Hadron Collider (LHC). This dissertation presents the results of a search for new heavy resonances (denoted as ���X���) with spin-0 and spin-2 decaying into HH at the LHC in the bbW+W��� channel, specifically: X ��� HH ��� bbW+W��� ��� bbl+��l�����. It uses 137.6 fb���1 proton���proton collision data at a center-of-mass energy of 13 TeV recorded by the Compact Muon Solenoid (CMS) detector from 2016 to 2018. The presence of two escaping neutrinos in the final state leads to an unconstrained kinematic system, making direct reconstruction of the heavy resonance mass impossible. To address this challenge, the search employs a new technique, called the Heavy Mass Estimator (HME), which estimates the heavy resonance mass in a probabilistic approach. Additionally, compared to an earlier CMS search using only 2016 data, this search extends event selection criteria to enhance signal acceptance and adopts an advanced machine learning architecture. These two enhancements alongside the HME technique significantly increase sensitivity, achieving 2 to 5 times greater sensitivity compared to the 2016 search, assuming the same amount of data. No statistically significant evidence for new heavy resonances is found within the data. Upper limits at a 95% confidence level are set on the production cross sections of new resonances decaying into HH. These limits vary from 7.149 pb to 0.030 pb for spin-0 resonances and from 5.569 pb to 0.023 pb for spin-2 resonances, in the mass range from 250 GeV to 900 GeV
The Addition of Cyanoacrylate Adhesive to Knots of Various Suture Loops: A Study on Tensile Strength and Suture Loop Integrity
No full textCyanoacrylate adhesive is used by some practitioners in conjunction with sutures to secure free gingival grafts to a surgical bed, in conjunction with sutures to function as a dressing for palatal harvest sites or biopsy sites, or to help maintain primary closure with bone grafting procedures. There is limited research regarding the effects of cyanoacrylate adhesive on the mechanical properties of sutures in an oral environment. Therefore, the aim of this study is to determine whether or not the addition of cyanoacrylate adhesive to suture loops impacts suture maximum tensile strength or cause of suture failure under tension.
60 samples of each suture were tied around 5 PEX pipes using a three-throw surgeon���s knot. Cyanoacrylate adhesive was applied to half of the suture knots as per the manufacturer���s instructions. The rods containing the sutures were then immersed in an artificial saliva solution and the pH and temperature were monitored. 5 suture samples of each suture type from the cyanoacrylate group, and 5 sutures of each suture type from the non-cyanoacrylate group were tested for maximum tension at the following time points: prior to submersion, 24 hours post-submersion, 3 days post-submersion, 7 days post-submersion, 10 days post-submersions, and 14 days post-submersion. Maximum tensile strength, reason for suture failure, and location of suture failure were recorded.
PGA-PCL sutures showed a 37% incidence of knot slippage when cyanoacrylate was not added to the knot. The addition of cyanoacrylate resulted in a 0% incidence of knot slippage (p=0.0048). The cause of suture failure for PTFE was always knot slippage, regardless of the addition of cyanoacrylate. On the other hand, silk, polypropylene, chromic gut, and PGA loops always failed due to suture loop breakage, regardless of the addition of cyanoacrylate. The addition of cyanoacrylate resulted in a statistically significant difference in maximum tensile strength of monofilament sutures (p=0.00041), synthetic sutures (p=0.00018), and absorbable sutures (p=0.0000031). The adhesive also improved maximum tensile strength of suture loops for silk (p=0.00088), PTFE (p=0.0091), PGA (p=0.029), and PGA-PCL sutures (p=4.4E10������), but not for polypropylene (p=0.45) or chromic gut sutures (p=0.87). The effect of the addition of cyanoacrylate to PGA-PCL was statistically significantly different at all days, except for day 14 and the retentive effect of cyanoacrylate appeared to decrease with time.
The addition of cyanoacrylate adhesive eliminates knot slippage in PGA-PCL sutures and increases the maximum tensile strength of silk, PTFE, PGA, and PGA-PCL sutures. These findings suggest that the addition of cyanoacrylate adhesive to suture knots may enhance suture loop integrity in an oral environment
A Characterization of the Vertical Structure and Mixing of the Eastern Mediterranean Sea
No full textObservational data collected by THEMO (The Texas A&M - University of Haifa Eastern Mediterranean Observatory) is used to characterize the seasonal variability of the water-column to understand the vertical structure and vertical mixing of the Levantine Basin in the Eastern Mediterranean Sea. Previous studies have shown the marginal Eastern Mediterranean Sea is characterized by hypersaline waters, strong water-column stratification, and regular seasonal atmospheric patterns. THEMO is composed of two surface buoys located off the coast of Haifa, Israel: one shallow buoy (water depth of 125 m; 10 km from shore) in the coastal zone of the Levantine Basin, one deep buoy (water depth of 1430 m; 60 km from shore), and one StandAlone McLane Moored Profiler (MMP), which is deployed close to the deep buoy. These instruments and buoys provide in-situ near real-time subsurface physical oceanographic observations and atmospheric observations of the Eastern Mediterranean Sea. The objectives of this research are: 1) to characterize and identify the processes that force the seasonality of the surface mixed layer depth, 2) to quantify the mechanisms that drive the hydrographic variability of the upper (surface to 1400 m depth) water-column, and 3) to categorize the stability processes of the Eastern Mediterranean Sea upper water-column using Turner Angle (Tu). Results show that the mixed layer depth varies seasonality from 250 m in Winter to less than 85 m in non-Winter months and is correlated with relatively stronger winter wind speeds (average of 7.12 m/s (Winter) to 4 m/s (non-Winter)). The upper 100 m of the water-column also experiences warming of 2 degrees C during Winter due to enhanced downward mixing of warm surface water with cooler subsurface water. Statistical analysis using empirical orthogonal functional (EOF) analysis shows that outside Winter months, variance in the principal component time-series is most correlated with the geostrophic current direction and accounts for about 50% of the total variance of water-column temperature and salinity. Characterization of water-column stability shows stable waters (-45 degrees < Tu < 45 degrees), i.e., no overturning, are most likely to occur in the upper 200 m of the water-column, and double diffusive mixing through salt fingering occur in waters below the mixed layer depth. The depth of salt fingering and stability are similar to other areas of the deep Eastern Mediterranean Sea and mid-latitude marginal seas of the world ocean
Efficacy and Utility of MPP51AA2-Traited Cotton as a Management Tool for Cotton Fleahoppers [Pseudatomoscelis seraitus (Reuter)]
No full textIn Texas the cotton fleahopper (Pseudatomoscelis seriatus (Reuter)) is considered a highly economically damaging pest of cotton (Gossypium hirsutum L.). Current control methods rely heavily on the use of foliar applied chemical insecticides during the growing season. The Mpp51Aa2.834_16 gene in cotton (ThryvOn) has proven effective against thrips and Lygus spp. with piercing and sucking feeding behaviors, suggesting the trait may also provide similar efficacy on cotton fleahoppers.
Field trials were conducted in 2019, 2020, and 2021 comparing a ThryvOn cultivar to a non-traited isoline under insecticide-treated and untreated conditions. While cotton fleahopper population differences between the traited and non-traited plants were not consistently noted during the pre-bloom squaring period, there was a consistent increase in square retention in cotton expressing Mpp51Aa2 relative to non-traited cotton. Additionally, cotton expressing Mpp51Aa2 offered similar square protection relative to non-traited cotton treated with insecticides for cotton fleahopper. These findings indicate that the Mpp51Aa2 protein should provide benefits of delayed nymphal growth, population suppression, and increased square retention.
In the choice assay, feeding by cotton fleahoppers significantly reduced square retention in the non-traited cotton to 46%, while ThryvOn cotton retained 60% of squares. In the no-choice assay, cotton fleahopper nymph feeding significantly reduced square retention in the non-traited cotton to 61%, whereas ThryvOn cotton was unaffected. Our findings indicate that the Mpp51Aa2 protein influences cotton fleahopper feeding preference and the susceptibility of cotton plants to damage caused by cotton fleahoppers.
To evaluate the feeding behavior of the cotton fleahoppers on ThryvOn cotton an electropenetrography (EPG) coupled with a Giga-8 DC EPG amplifier was used to monitor the probing activity cotton fleahopper nymphs on ThryvOn and non-traited cotton squares. Nymphs were placed on a square for 8 hours and waveforms were characterized as non-probing, cell rupturing, and ingestion. There were significantly more cell rupturing events on ThryvOn (14.8) than on non-traited squares (10.3) but were no differences in ingestion events. However, the duration of ingestion events were significantly shorter at 509s on ThryvOn compared to 914s on non-traited squares. The results of this study provide evidence that ThryvOn affects the feeding behavior of cotton fleahoppers
Optimizing Markov Decision Process Models of Intermittently-Observed Multi-Agent Systems
No full textA challenging category of robotics problems arises when sensing incurs substantial costs. This thesis examines settings in which a robot wishes to limit its observations of state, for instance, motivated by specific considerations of energy management, stealth, or implicit coordination between multiple agents. We consider the problem of planning under uncertainty when a robot���s observations are intermittent under two specific circumstances. In one, their timing is known via a pre-declared schedule, whereas in the other the timing arises dynamically from multiple robots working together to generate observations.
After establishing the appropriate notion of an optimal policy for each setting, we find that the pre-declared case requires tackling the problem of joint optimization of the cumulative execution cost and the number of state observations, both in expectation under discounts. To approach this multi-objective optimization problem, we introduce an algorithm that can identify the Pareto front for a class of schedules that are advantageous in the discounted setting. The algorithm proceeds in an accumulative fashion, prepending additions to a working set of schedules and then computing incremental changes to the value functions. Because full exhaustive construction becomes computationally prohibitive for moderate-sized problems, we propose a filtering approach to prune the working set. Empirical results demonstrate that this filtering is effective at reducing computation while incurring only negligible reduction in quality. In summarizing our findings, we provide a characterization of the run-time vs quality trade-off involved.
We explore as well the dynamic observation scenario, by developing a formulation for renegotiation of observations throughout execution. The formulation is additionally expanded to support the navigation of multiple agents in a single, joint MDP. We conclude with a hardware demonstration featuring two robots maintaining formation whilst moving down a corridor, subject to motion uncertainty and turning to look at each other intermittently to gauge their states
Enhancing Control Assessments and Risk Analysis in Batch Chemical Processes: A Focus on Safer Design Methodologies
No full textBatch and semi-batch processes involving critical chemical reactions pose significant risks to industrial safety and require rigorous control assessment and risk analysis. This study aims to survey current industry practices and methodologies for testing and assessing the controls in batch reactions. It identifies strengths and limitations in existing procedures and propose safer design methods to mitigate reactive hazards. In batch reactions, a diverse range of chemicals operates at dynamic parameters such as temperature and pressure. Assuming the worst case scenarios and improper evaluation of controls could lead to events with dire consequences. The study examines the typical tests conducted for batch reactions and identifies opportunities for optimization based on the outcomes. Layer of Protection Analysis is used to evaluate various preventive controls such as Inherently Safer Designs (ISDs), automated systems and relief sizing. Recognizing the pivotal role of critical controls such as quenching and relief sizing as the last line of safeguards in the batch processes, here we determine what are the different ways of performing quenching process to halt the reaction and the effective way of doing this operation. We also develop a model and calculate for effective quenching during worst-case scenarios, demonstrating how this proposed safer design method maximizes control functionality and minimizes risk. As relief is also considered in many cases where quenching is not practical, the relief sizing of reactive systems is quite complex and here we compare how drastic the change in relief size would be for a reactive system when compared to relief sizing performed in a conventional way. Another concern highlighted is relying solely on automated systems, which can lead to catastrophic consequences in case of process deviation. This research scrutinizes the conditions which are considered over conservatively by many of the process Industries, arriving at conclusion of adequacy in the Safety Systems and its impact on the availability of the Safety System on demand (PFD) using exSILentia tools. Overall, this study comprehensively explores industry practices in testing, standard controls and alternate safer designs along with conservative safety system settings