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Structural Analysis of Irregular Cracking in Continuously Reinforced Concrete Pavements
No full textThis research study explores the analysis of irregular cracking in continuously reinforced concrete pavements (CRC) using a synergized approach of analytical and numerical methods. A Python script was developed to execute linearized finite difference analysis, assessing temperature and moisture profiles to compute environmental stresses, including thermal and shrinkage effects. This script integrates these stresses with user inputs to run finite element analysis using the ABAQUS solver. Concurrently, the study provides a revision of the AASHTO crack spacing formula presented in the Mechanistic-Empirical Pavement Design Guide (MEPDG) for CRC pavements. The modified formula addresses the limitations of the previous version, providing insight into the depth of crack initiation. The study uncovers several key insights into early-age cracking in continuously reinforced concrete pavements including -but not limited to- variations in temperature and moisture profiles across different locations and seasons that significantly impact the cracking mechanism. Longitudinal steel cover is found to be a critical factor, with smaller cover increasing the likelihood of top-down. The study also reveals that while active cracking control is effective in determining crack locations, its efficiency is compromised when the bonding to the underlying layer is weak. Ultimately, the high bonding strength between PCC slabs and the underlying layer not only increases the possibility of bottom-up cracking but also decreases crack spacing
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
John Bickham field notebook: AK17001-AK17500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for AK17501-AK18000 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
Contact Mechanics and Tribology of Thermal and Electrostatic Friction Modulation for Surface Haptics
No full textHaptics, an integral part of human-machine interaction, offers a crucial sense of touch for immersive user experiences in many applications, such as virtual and augmented reality. While audio-visual interfaces have been significantly developed, seamlessly integrating touch sensation into these interfaces encounters hurdles due to mechanical and neurophysical complexities of the interaction of human skin with the physical world.
Surface haptics presents a promise for integrating touch into the audio and video interfaces, particularly with the widespread use of touchscreens. Various forms of haptic feedback have been explored in the surface haptics field. Among them, friction modulation-based haptic feedback has been demonstrated as an effective way to offer users a sense of virtual shapes and textures on surfaces. This method, however, has challenges such as variability in frictional performance. This variability hampers consistent user feedback and impedes device commercialization. To address the variability issue, this research aims to elucidate the impact of humidity on friction under electroadhesion based on the electrowetting effect and provides insight into the device design for more consistent haptic feedback. Understanding the intricate surface topography of the human fingerpad, which significantly influences contact mechanics, is another critical aspect. We examine the surface topography of the fingerpad in detail across scales and investigate its impact on contact mechanics studies. Moreover, the surface temperature is another factor that causes the variability of the frictional performances in the surface haptic devices. This work aims to understand the underlying mechanism of the surface temperature effect on friction to provide insight into device design for more consistent haptic feedback and propose a new method to modulate localized friction at lower operating voltages.
Additionally, the development of the 'Touchbot,' a wearable intermediary device, aims to overcome limitations in current surface haptics by providing localized tactile feedback in both lateral and normal directions across the contact patch, thus enhancing the realism of 3D rendering of virtual features. This study will focus on the building block of the Touchbot, an electroadhesive (EA) puck with high EA shear stress and high durability. We look into a more in-depth electromechanical point of view of EA devices, which offers a foundation for EA devices beyond this project
Multi-Tiered Systems of Support: Implementation Experiences of High School Principals
No full textThis study aimed to explore the Multi-Tiered Systems of Support (MTSS) implementation experiences of three high school principals and their assistant principals in one North Texas public school district. The study utilized qualitative methods and case study design to better understand the principals��� overall impression of MTSS implementation and their suggestions for improving the conditions that may have hindered the implementation of MTSS on their campuses. The findings presented in this study are the analysis of data acquired through the Self-Assessment of MTSS Implementation (SAM) survey, the principal interviews, and document analysis. The analysis was guided by implementation science as proposed by Fixsen and Blas�� (2008). This analysis of the data showed that the three high schools in the study have stalled in their MTSS implementation efforts after five years, mostly during the program installation phase, despite their best efforts. To move the high schools forward from the program installation stage to the full operation stage on the implementation science continuum, I proposed recommendations that address the three main drivers of successful implementation: leadership drivers, organization drivers, and competency drivers. By systematically addressing these drivers, the high schools in the study can progress toward full implementation of MTSS
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
Teleoperation for Time-sensitive and Challenging Construction Environments: Dive into Cognitive Challenges
No full textDespite the dream of fully autonomous construction robots, the inherently unpredictable and dynamic scenarios of construction tasks make complete automation challenging. In many scenarios, situations that are outside the planned tasks or the pre-programmed robots��� capabilities underscore the necessity for human adaptability and decision-making. Teleoperation, therefore, has emerged as an effective approach in the construction domain and has been extensively studied. In the past two decades, prior studies primarily focused on technological advancements such as sensing for distant workplaces, computation algorithms, and automated control systems. However, this focus often neglected one crucial element of the teleoperation system: the human operator. As humans are decisionmakers and vital in addressing construction challenges effectively, a more in-depth understanding of human operators is necessary. Particularly, we must dive into the limited human cognition capacity and the challenges it poses during construction teleoperation, as cognitive workload directly influences their decision-making quality and control performance. This study thus employs a human-centric approach to navigate and manage the cognitive challenges faced by operators during the teleoperation of construction robots, especially those focused on the excavators. There are three research objectives: (1) the first objective aims to explore human factors that significantly affect teleoperation performance in construction from a systematic perspective, this objective involves identifying and prioritizing factors focused on cognitive aspects to understand their impact on operational efficiency and safety; (2) the second objective examines how various demanding and challenging construction scenarios impact teleoperators' cognitive and task performance along with safety behavior, this objective seeks to deepen understanding of the impact of the cognitive challenges identified in the first objective; and (3) the third objective is to assess the effectiveness of a novel assistive technology that has been specifically designed to reduce cognitive load and promote safer and more efficient performance, even under highly demanding conditions towards a cognitive-resilient teleoperation system. The findings reveal that excavator performance is negatively affected not only by tangible obstacles but also by intangible obstacles that impact the operator's cognitive state, such as time pressure and risk perception in remote environments. During our investigation, we found that teleoperators conducting demanding tasks performed the best under reasonable time pressure, even better than without pressure, whereas under excessive time pressure, they experienced cognitive overload and impaired risk perception, resulting in significant control errors as a result. However, teleoperators using electro-tactile feedback, a novel assistive technology, achieve high levels of safety and productivity regardless of the level of time pressure. This assistive technology is shown to help prevent cognitive overload by distributing cognitive tasks to the robotic system, enhancing awareness of remote hazards. This dissertation significantly contributes to the body of knowledge of construction teleoperation by bridging the gap in understanding human aspects within teleoperation systems. The research also offers valuable insights for designing user-centered systems for human-robot interaction or collaboration in construction teleoperation, applicable across various scenarios ranging from normal to highly demanding and challenging workplaces
John Bickham field notebook: AK14001-AK14500.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for AK14501-AK15000 corresponding to unique identifiers of specimens/samples examined for biological research. Specimens are primarily housed at Texas A&M University; Biodiverstiy Research and Teaching Collection
University Faculty Perceptions About Disability, Accommodations, and Access
No full textOpportunities and expectations for students with disabilities to earn a postsecondary degree have grown over recent decades. Despite positive improvements, disabled students lag behind non-disabled peers in degree attainment. Simultaneously, growing numbers of disabled students are enrolling with increasingly complex experiences, including a significant growth in mental health conditions among college students, and institutions of higher education are struggling to respond.
Faculty and staff in higher education have noticed these trends, but have done little more than keep up with increasing demands. Though prior researchers have long focused on the experiences of students, considerably less effort has been put into understanding the experience of faculty or staff involved in creating disability access. Faculty experiences are essential to understand because of their critical role in disability access.
Prior research on faculty experiences teaching disabled college students has largely featured survey-based, quantitative designs that have provided valuable aggregated insights, but offer little context of their faculty participants or the factors behind their responses. The purpose of this study was to qualitatively assess faculty experiences and perceptions of teaching students with disabilities. Faculty participants with at least five years of experience were recruited from a single, culturally bound university.
This study yielded data that add new insights to the literature, and implications for practice. The findings identified faculty hold strong, paradoxical views about bureaucratic systems that shape how disability access occurs in a university setting. Specifically, they have a dynamic and interactive relationship with the systems at hand, which are modified through relationships and trust of those involved. Faculty were generally supportive and positive of disabled students and disability resource staff, while simultaneously questioning and fearing the bureaucratic system deployed to ensure disability access. This study situated participant perspectives relative to their experiences navigating institutional systems, and therefore adds factors related to bureaucracy and trust to the literature, while also confirming a variety of prior researcher���s findings. While this study contributes new insights to the literature and best practices, further research is needed to ensure faculty are adequately prepared and supported when teaching disabled students
Selective Aryl Hydrocarbon Receptor Modulators as a Potential Treatment for Major Depressive Disorder
No full textMajor depressive disorder (MDD) is a worldwide public health concern, and although treatments exist, many people still suffer from treatment resistant depression. The projects in this dissertation aimed to evaluate the feasibility of using selective aryl hydrocarbon modulators (SAhRMs) as a treatment for MDD. The aryl hydrocarbon receptor (AhR) is a ligand-activated intracellular transcription factor that is involved in numerous biological processes which are linked to potential causes of MDD. Two SAhRMs, 3,3���-diindolylmethane (DIM) and 1,4-dihydroxy-2-napthoic acid (DHNA) were tested for their ability to prevent and treat MDD-like behavior in female mice using unpredictable chronic mild stress (UCMS). Depression- and anxiety-like behaviors were examined using a battery of behavioral tests. In the first project, both SAhRMs prevented and reversed depression-like behavior but had little effect on anxiety like behavior. An isomer of DHNA, which is inactive at the AhR, did not prevent depression-like behavior, hinting at a role for AhR activity in the antidepressant action of DHNA. In the second project, male mice were examined, and SAhRMs did not act as antidepressants but had some effects on anxiety-like behavior in males. There was no effect of SAhRMs on spatial learning or on weight gain in stressed or unstressed male or female mice. The third project tested mice which do not express the AhR in the internal epithelium (AhR��IEC). AhR��IEC mice were resilient to the effects of stress on depression-like behavior, suggesting a role for intestinal AhR in maintaining depression- like states. Additionally, SAhRMs prevented depression-like behavior in these mice, effectively eliminating the intestinal epithelium as a potential site of action for SAhRMs. Limitations, possible mechanisms, and applications are discussed. The results of these studies indicate a potential for SAhRMs to be developed as a treatment for MDD and highlight the need to further investigate the role of AhR in MDD