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Soil Temperature and Moisture Control in Ground Source Heat Pump Systems
No full textThis numerical study focuses on exploring passive methods to control soil temperature rise and restore favorable thermal conditions in ground source heat pump (GSHP) systems. The three methods investigated were soil moisture control, presence of thermosiphon (TS), and effects of soil type. A single U-loop of a GSHP system was modeled in a soil domain using a finite element analysis (FEA) software Ansys Mechanical. The Backward Euler formulation and the Sparse Direct Solver were used to discretize and solve the governing heat conduction equation. Four moisture contents (high, low-to-high, high-to-low, low) and two soil types (sandy loam, clay loam) were considered, along with the presence (TS case) and absence (non-TS case) of a single thermosiphon. Soil temperature profiles were plotted at multiple points to examine the effects of moisture level and soil type, and the temperature difference between TS- and non-TS cases was plotted to study the thermosiphon effect. Curve-fitting of soil temperature profiles was done to quantify the rate of soil temperature rise at different depths. The results showed that soil temperatures decreased with moisture content. Soil temperatures were lower for TS cases than for non-TS cases, and the TS effect also decreased with moisture content. Moreover, clay loam resulted in higher soil temperatures than sandy loam at all moisture levels considered. In summary, to maintain and restore soil thermal conditions favorable to GSHP systems, moisture control is recommended for GSHPs in high thermal diffusivity soils, while thermosiphon use is preferred for GSHPs in low thermal diffusivity and dry (low moisture content) soils
The Formulation of a Consequence-Informed Methodology for the Design of Physical Protection Systems at Advanced Commercial Reactor Facilities
No full textThe survivability of the domestic nuclear power industry depends on the cost-competitiveness of safe and secure nuclear power generation. Advanced reactor design concepts aim to have increased safety margins over traditional large Light Water Reactors (LWRs). With increased safety margins comes the potential for a corresponding decrease in off-site risk to the general public from a hypothetical release of radioactivity caused by an accident or deliberate sabotage. Without sacrificing safety or security, advanced reactor designers may be able to achieve capital and operational cost improvements over current LWRs, in part, by designing less burdensome Physical Protection Systems (PPS), and by placing response forces off-site. To accommodate these developments, the U. S. Nuclear Regulatory Commission (NRC) is drafting new regulations for physical security when licensing through the current 10 CFR 50 or 52, along with drafting an entirely new licensing framework, 10 CFR 53.
This dissertation presents a novel technology-inclusive consequence-informed methodology for the selection of the optimal licensing path for the design of Physical Protection Systems (PPS) at advanced fixed-site commercial nuclear power facilities, and applies the methodology to a hypothetical reactor facility containing a microreactor design. The resulting methodology incorporates current and proposed regulatory limits for off-site dose consequence to the general public to guide the licensing applicant in choosing the licensing pathway which best suits their desired financial costs and PPS design characteristics. For the methodology application to a microreactor site, newly allowed PPS characteristics in proposed NRC draft regulations were incorporated into the ultimate PPS design. MELCOR code analysis of potential adversary-executed sabotage actions, and off-site doses predicted by the MACCS code, were coupled to determine off-site consequence of the facility while PathTrace and SCRIBE 3D were used to develop a PPS model of the facility for effectiveness testing. The resulting PPS was compared to a PPS at the same facility designed following traditional security licensing requirements in 10 CFR 73. Results of the comparison demonstrated an increase in necessary capital costs for the construction of a facility with enough delay to accommodate a 30-minute off-site response force response time. However, the reduction in security force staffing showed the potential for significant savings in operational staffing
Evaluation of the Interaction of an Insecticidal Peptide and Bt Proteins or a Baculovirus for Managing Helicoverpa zea in Bt Cotton
No full textThe cotton bollworm, Helicoverpa zea (Bobbie), is a major and damaging pest of cotton, corn, sorghum, and other crops. This pest has developed field-evolved resistance to the Cry1 and Cry2 Bt proteins, and there are early warning signs for resistance to Vip3Aa. Chlorantraniliprole is the primary insecticide used to manage H. zea in sorghum and Bt-resistant H. zea in cotton. There is concern that overutilization of chlorantraniliprole may lead to resistance. Utilizing IPM-friendly biopesticides may be an alternative means for managing H. zea in cotton and sorghum. Spear RC (HXTX) is a new biopesticide derived from spider venom, but because this product requires aid from Bt to penetrate the mid-gut, its utility is diminished. However, cotton expressing Bt proteins may be able to serve as facilitators although it is uncertain if they will function for Bt resistant H. zea. Alternatively, Heligen (HearHPV), a Heliothine-specific virus, may also act as a facilitator for HXTX.
Experiments were conducted to determine the interaction between Bt proteins and HXTX on Bt-susceptible, Cry-resistant, and Vip-resistant H. zea. In diet-based bioassays in the absence of any Bt proteins, HXTX alone exhibited marginal activity on susceptible, Cry-resistant, and Vip-resistant H. zea, but when combined with overlays of 10��g/cm�� of Cry1Ac, toxicity to Cry-resistant H. zea was higher. However, the addition of 5��g/cm�� of Vip3Aa39 did not enhance HXTX toxicity to Vip-resistant H. zea. This suggests that Vip3Aa resistance probably involves binding site resistance, while Cry-resistance probably allows binding and some pore formation. Thus, Cry1Ac Bt protein expressed in cotton will serve as an effective facilitator toward H. zea that are resistant to Cry1Ac.
Diet-based bioassays were used to determine if HearNPV may serve as a facilitator for HXTX targeting Bt-susceptible and Cry-resistant H. zea. Neither HXTX alone nor HearNPV alone at LC������ and LC������ dosages had great activity towards H. zea. Against Bt-susceptible H. zea, when HXTX was combined with HearNPV there was a significant interaction and synergistic effect, but this relationship was not as pronounced with the Cry-resistant H. zea strain. Thus, HearNPV may serve as facilitator for HXTX, but it appears to be less consistent than Bt proteins.
In 2022-2023, field tests were conducted to field validate laboratory findings demonstrating the potential of utilizing HXTX for H. zea management in non-Bt and Bt cotton. Despite laboratory assays suggesting that HXTX has activity on H. zea when used in conjunction with Bt proteins, we were unable to demonstrate significant activity in cotton in the field. This was mostly likely due to inadequate spray coverage, residual persistence, and the lack of translaminar activity for HXTX
Raman Spectroscopy as a Diagnostic Tool for the Detection of Tomato Brown Rugose Fruit Virus
No full textTomatoes and peppers together constitute a billion-dollar industry in the United States alone, which speaks highly of their importance to growers and the United States Department of Agriculture (USDA) alike. These crops, however, are host to a destructive virus, tomato brown rugose fruit virus (ToBRFV). Due to its ability to overcome all tobomovirus resistance genes, including Tm-2��, there are no known resistant varieties for ToBRFV. Therefore, many regulations are in place in hopes of controlling its spread, yet it continues to spread to many areas around the world, constituting a global epidemic. Raman spectroscopy (RS) is a noninvasive tool that scans a sample and uses the interaction of light and molecules to give a resulting spectrum of scattered light that can be used for analysis. This tool for detecting chemical compounds is already popular in many fields and has recently even been a growing research endeavor for disease diagnostics in plant pathology, where it has shown great promise with a wide variety of diseases. In this study, we examine ToBRFV as well as tobacco mosaic virus (TMV) and aim to determine if RS can be used as a diagnostic method to aid in management practices. We hypothesize that we will be able to observe differences in spectral peaks between healthy and infected plant/seed tissue with control, TMV, and ToBRFV groups. After inoculation, scanning, and Matlab analysis, it was demonstrated that there were spectral differences between healthy and infected plants, as well as differences between TMV and ToBRFV-infected plants. Additionally, this experiment was done on pepper seeds and preliminary data was obtained which displayed spectral differences between pepper seeds infected with ToBRFV and control seeds, showing potential support for this notion on seed tissue as well. Results suggest that RS does show promise to be incorporated as a diagnostic method and may provide useful insight into virus distribution throughout plants. Based on the results obtained in this study, there is potential for future work to take place on the basis of this data
Using Stimuli-Responsive Material for the Design and Fabrication of Artificial Muscles
No full textStimuli-responsive materials that change shape (i.e., elongate, contract, and/or twist) when exposed to an appropriate stimulus are promising candidates to replace traditional machines in biomedical devices. This dissertation explores the innovative use of stimuli-responsive materials in addressing the challenges of treating stress urinary incontinence (SUI), a condition that affects nearly 50% of women during their lifetime. Current treatments for SUI are associated with complications leading to undesirable outcomes such as postoperative voiding dysfunction. The research, divided into four key chapters, focuses on the development and application of artificial muscle devices based on two distinct stimuli-responsive materials ��� Liquid Crystal Elastomers (LCEs) and Magnetoactive Elastomers (MAEs) for the potential treatment of SUI.
In Chapter I, the dissertation commences with a comprehensive introduction to stimuli-responsive materials, elucidating their pivotal role in the design and fabrication of artificial muscles. Emphasizing the versatility of two materials (LCEs and MAEs), the chapter provides a foundation for their application in the subsequent chapters. Chapter II delves into the pathophysiology of SUI, providing a thorough overview of the condition, including its causes, prevalence, and impact. This section establishes the contextual framework for the subsequent exploration of the subsequent development of LCE and MAE-based devices for urethral support. We also provide relevant information that must be considered when designing in vitro models of the urinary tract and selecting appropriate animal models to evaluate devices. Chapter III focuses on the design, fabrication, and in vitro and in vivo evaluation of a dynamic urethral support device based on LCEs. In Chapter IV, I extend the exploration to MAEs and investigate their integration into a dynamic urethral support device. MAE-based devices were fabricated, characterized, and then evaluated using a simple in vitro urinary system simulating the effects of stress or cough.
Collectively, this dissertation contributes to the interdisciplinary field of biomedical engineering by integrating stimuli-responsive materials with innovative solutions for SUI. Investigating the potential of LCEs and MAEs in providing adaptive and customizable support, this dissertation presents a novel approach to addressing SUI through advanced materials. The findings presented herein pave the way for further advancements in the design and fabrication of artificial muscles, offering hope for improved therapeutic interventions for complex healthcare challenges
A New Galerkin Quadrature Method Without the Requirement of Matrix Inverse
No full textA new method of forming the scattering source of the Boltzmann neutron transport equation for anisotropic scattering is proposed through the use of Grahm-Schmidt orthogonalization. This new method builds upon two previous methods but differentiates itself by lowering the computational burden of the calculation and potentially admitting more general types of quadratures. It is hoped that this method will gain greater traction in codes solving the Boltzmann neutron transport because of its lower cost and wider applicability. The Galerkin Quadrature method is required for highly anisotropic scattering, which characterizes charged particle transport, and was originally developed for this purpose. This thesis presents the sum of research into the new Galerkin Quadrature method in the form of a paper submitted to the Journal of Nuclear Science and Engineering, 2024. The derivation of all 3 Galerkin Quadrature methods are defined, the test problems are stated with their results, and conclusions drawn. An additional summary section details the conclusions of the overall work
Theory and Applications of Mixed-Integer Fractional Programming
No full textThis dissertation is focusing on developing theoretical and practical results for a class of mixed-integer problems with fractional objectives. We introduce the generalized clique relaxation models with fractional objectives, namely the maximum ratio s-plex problem and the maximum ratio s-defective clique problem. We establish complexity results, describe solution methods, as well as introduce valid inequalities that are shown to substantially improve the performance of the proposed formulations. Then we we discuss the application of Bron-Kerbosh algorithm for solving fractional clique relaxation problems. We develop a new efficient combinatorial approach best suitable for sparse graphs. Finally, propose an extension of knapsack problems with fractional objectives arising from applications in service systems design and facility location problems with congestion
Dry Cell Radiation Field Characterization at the Texas A&M University Nuclear Engineering and Science Center
No full textThe Nuclear Engineering and Science Center at the Texas A&M Engineering Experiment Station routinely conducts experiments involving neutron and gamma irradiations with a 1-MW TRIGA research reactor. The Center is equipped with a dry irradiation cell, which can be used for experiments requiring a mixed neutron/gamma field. However, in recent years the dry irradiation cell has not been utilized and there exists no surviving information on the radiation environment inside the cell during operation. To resolve this, a full characterization of the neutron and gamma radiation environment inside the cell has been completed.
To fully characterize the neutron flux environment inside the dry irradiation cell, neutron activation analysis has been performed on two different configurations: one with shielding and one without shielding. The program STAYSL PNNL was employed to unfold the full neutron spectrum using the experimental results of the neutron activation analysis. Furthermore, thermoluminescent dosimetry has been utilized to calculate the absorbed gamma dose rates of silicon and tissue inside the cell for each configuration. Each technique has been utilized according to industry standard practices.
The results of this work have shown that adding shielding material to the dry irradiation cell window will have a significant impact on the quantity and energy of radiation which enters the cell. With no shielding present in the window, 50-kW reactor operation produces a neutron flux of 2.59E+09 and a gamma dose rate 50.84 krad/hr in silicon. When 8 inches of high-density polyethylene shielding and 0.8 inches of lead shielding are installed in the window, the neutron flux drops to 4.81E+07 while the gamma dose rate falls to 13.45 krad/hr in silicon
Isla Piedra: Coastal Shoreline Change of an Ancient Human Settlement on the Gulf of Mexico
No full textAlong the Gulf of Mexico, on the northwest corner of the Yucat��n Peninsula, sits the northern coastal plain of the State of Campeche. The shoreline of this plain is impacted by coastal processes and ecological succession based on low-energy waves that transport and deposit sediment. These processes form a muddy shoreline with extensive wetlands, characterized by estuaries, mangrove forests, floodplains (ci��nagas) and islands of vegetation known as hardwood hammocks (petenes). This dynamic ecological frontier is a transition zone between marine and terrestrial environments, perpetually undergoing change. Ancient human settlements of varying levels of complexity have been documented along this shoreline, all of which were subject to dynamic coastal processes���such as the case of Isla Piedra. However, there has been limited exploration into whether these dynamics have modified the landscape of these settlements over time. This research seeks to determine if the ancient inhabitants of Isla Piedra experienced a different coastal landscape compared to today and how this influenced their adaptive behaviors. First, the relationship between coastal geomorphology and ancient human settlements is established. Then, through change detection methods, a series of remote sensing satellite images of the coastline are analyzed to identify differences indicative of landscape changes. Based on the detected alterations, this research proposes potential shoreline changes that Isla Piedra inhabitants may have experienced during its primary period of ancient occupation. This change provides a foundation for future research about site formation and adaptive strategies developed by the island���s inhabitants
Oebalus pugnax (Hemiptera: Pentatomidae) Resistance to ��-cyhalothrin in Texas Grain Sorghum and Efficacy of Potential Alternative Insecticides
No full textAlong the Coastal Bend of Texas, the rice stink bug, Oebalus pugnax (F.), is a pest of grain sorghum and rice that is primarily managed by application of insecticides. In 2015, a rice stink bug population from Wharton County, Texas, was found to be resistant to the pyrethroid insecticide ��-cyhalothrin, a common insecticide for rice stink bug management. In more recent years, reports of control failures have spread throughout Coastal Bend, a major hub of Texas grain sorghum production. Despite growing concern from grain sorghum producers, no studies have thoroughly evaluated the extent or geographic range of pyrethroid resistance in Texas. This thesis focuses on addressing the gaps in knowledge regarding rice stink bug pyrethroid resistance in grain sorghum and improving management tools and considerations for this pest.
Between 2021���2023, 21 rice stink bug populations across the Texas and Louisiana were evaluated for ��-cyhalothrin resistance over three grain sorghum growing seasons (2021���2023). Mortality was assessed through glass vial exposures to eight concentrations (0, 0.03, 0.1, 0.3, 1, 3, 10, and 30 ��g/vial) of the pyrethroid ��-cyhalothrin. The concentration of ��-cyhalothrin required to kill 50% (LC������) of each population was estimated by probit analysis. Furthermore, the efficacy of insecticides including pyrethroid (��-cyhalothrin), organophosphate (dimethoate), and neonicotinoid (dinotefuran) insecticides were evaluated in field experiments conducted in Nueces County, Texas in 2021. The efficacy of these insecticides was evaluated for suppression of nymph and adult rice stink bug over the course of 22 days in experimental plots.
Our results indicated numerous rice stink bug populations along the Coastal Bend were resistant to ��-cyhalothrin with LC������ values ranging from 42���1,600 times more than a susceptible population. In a 2021 field efficacy trial, ��-cyhalothrin did not provide adequate control for rice stink bugs. Dinotefuran provided excellent control of nymphs, but dimethoate provided greater control of adult rice stink bugs. This study resulted in the approval of three Section 2(ee) bulletins for dimethoate products to be used on rice stink bug in Texas grain sorghum, thereby expanding the products available for control of this pest