136879 research outputs found
Sort by
Multiphysics Models to Predict the Peformance and Reliability of Electroadhesive Surface Haptic Devices
No full textHaptics refers to the sense of touch, and surface haptics is the branch of haptics that deals with the generation of tactile effects on touch surfaces to make user experiences more immersive and realistic. Electroadhesive surface haptic devices make use of electroadhesion to apply electrostatic forces at the human-device interface, which is then modulated to modulate the interfacial friction forces and generate tactile effects.
Devices that incorporate such state-of-the-art technology often face several reliability and performance issues in their nascent stages that need to be resolved to enable their successful commercialization. Predictive models play an important role in the development of such devices because they provide designers with efficient tools to explore a wide design space to find solutions, as opposed to relying on an inefficient and expensive trial-and-error approach. In this study, we investigate a few such challenges associated with electroadhesive haptic devices. We will identify the key mechanisms causing visible preferential deposition of fingerprint residue on specific regions of the surface of commercial electroadhesive haptic touchscreens and develop a multiphysics predictive model that can be used to explore solutions to tackle this issue. We will then develop a finger mechanics model that can predict the roughness perception produced by distributed haptic devices. This model will provide insights into which mechanics properties trigger the mechanoreceptors that contribute to roughness perception. Finally, we will develop a multiphysics model that couples the contact mechanics, capillary, and electrostatic phenomena at the interface and can provide fast and accurate predictions about the interfacial friction force ��� an important parameter than needs to be accurately represented to make correct predictions about the device performance. Together, these models will provide useful tools to haptic device designers to build better haptic devices in a quick and cost-effective way
Motion Control Analysis of Hydrofoil-Based Autonomous Surface Vehicle: An Integrated Approach Utilizing Moving-Mass-Actuated Stabilizer and Variable RPM Propeller Modeled with Computational Fluid Dynamics and Auto-Control Algorithm
No full textHydrofoil-based Surface Vehicles (HSVs) have garnered significant attention for their potential to achieve high speeds, low hydrodynamic resistance, and reduced energy consumption. This efficiency is primarily due to the vehicle���s hull being elevated above the waterline, leaving only the hydrofoils and propeller submerged to generate the necessary lift force to counterbalance the vehicle���s weight at operational speeds. This study aims to extend these advantages by developing an autonomous control system, thereby enhancing the operational capabilities of these vehicles.
This dissertation dedicates to overcoming the inherent stability challenges in the in-house developed hydrofoil-based Autonomous Surface Vehicle (HASV). This battery-powered HASV leverages hydrofoil to lift its superstructure above the water, significantly decreasing drag and improving efficiency at cruising speeds. However, the design, which incorporates a single mast connecting the superstructure to the substructure, introduces notable stability issues. These challenges primarily arise from nonlinear flow loading on the hydrofoil substructure and external environmental factors such as ocean waves and currents. This complexity necessitates the development of an effective control system.
In response to these challenges, the study introduces an innovative control system utilizing the Proportional-Integral-Derivative (PID) algorithm to regulate the HASV���s pitch, roll, and heave stability. It includes a novel moving-mass-actuated (MMA) stabilizer in conjunction with an adjustable revolutions-per-minute (rpm) propeller. The MMA stabilizer enables dynamic adjustment of the HASV���s center of gravity, enhancing control over pitch and roll movements. Simultaneously, the propeller���s rpm is continuously modulated to manage thrust, thereby adjusting the lift force generated by the HASV substructure, which is crucial for controlling heave motion stability.
Previous research on HASV stability control primarily relied on either physical model testing or mathematical modeling. While physical model testing is comprehensive, it is often prohibitively expensive and time-consuming. In contrast, mathematical models, though efficient, require significant simplifications, frequently failing to fully capture complex physical processes, especially those with strong free surface effects. Given the HASV���s limited stability and pronounced free surface effects, there is an urgent need for a more effective and practical approach to investigate and optimize the PID control system. Addressing this need, the study proposes a more accurate Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD-based control investigation approach. This approach integrates a PID controller into the URANS CFD model, combining the detailed analysis capabilities of CFD with the precision of PID control. This integration ensures that the performance of the proposed control system can be precisely investigated and optimized under different diverse operational scenarios.
This study first starts with the CFD-based hydrodynamic performance analysis of a 2D dual hydrofoils with different configuration and generated a dataset, the dataset is then used to train an Artificial Neural Network (ANN) in order to use the ANN to interpolate within the interesting range and generate a finer resolution results. This analysis helps to have a basic understanding of how the wing and tail can interact with each other and laying the ground for the design of the submerged portion (substructure) of the HASV. Later, this study continues with a scaled-down experimental setup and procedure designed to test the hydrodynamic characteristics of the HASV���s substructure. This experimental study resulted in an understanding of the drag and lift behavior of the substructure, which is be used in the validation of the 3D CFD model. Then, this study continues to use the validated 3D CFD model as a tool to apply the CFD-based control investigation approach, mentioned above, to optimize the performance of the PID controller for regulating the HASV���s roll, pitch and heave motion. Then the effectiveness of the optimized control system on these three DOFs is tested using the CFD-based control investigation approach under different loading scenarios (calm water and waves)
Motion Control Analysis of Hydrofoil-Based Autonomous Surface Vehicle: An Integrated Approach Utilizing Moving-Mass-Actuated Stabilizer and Variable RPM Propeller Modeled with Computational Fluid Dynamics and Auto-Control Algorithm
No full textHydrofoil-based Surface Vehicles (HSVs) have garnered significant attention for their potential to achieve high speeds, low hydrodynamic resistance, and reduced energy consumption. This efficiency is primarily due to the vehicle���s hull being elevated above the waterline, leaving only the hydrofoils and propeller submerged to generate the necessary lift force to counterbalance the vehicle���s weight at operational speeds. This study aims to extend these advantages by developing an autonomous control system, thereby enhancing the operational capabilities of these vehicles.
This dissertation dedicates to overcoming the inherent stability challenges in the in-house developed hydrofoil-based Autonomous Surface Vehicle (HASV). This battery-powered HASV leverages hydrofoil to lift its superstructure above the water, significantly decreasing drag and improving efficiency at cruising speeds. However, the design, which incorporates a single mast connecting the superstructure to the substructure, introduces notable stability issues. These challenges primarily arise from nonlinear flow loading on the hydrofoil substructure and external environmental factors such as ocean waves and currents. This complexity necessitates the development of an effective control system.
In response to these challenges, the study introduces an innovative control system utilizing the Proportional-Integral-Derivative (PID) algorithm to regulate the HASV���s pitch, roll, and heave stability. It includes a novel moving-mass-actuated (MMA) stabilizer in conjunction with an adjustable revolutions-per-minute (rpm) propeller. The MMA stabilizer enables dynamic adjustment of the HASV���s center of gravity, enhancing control over pitch and roll movements. Simultaneously, the propeller���s rpm is continuously modulated to manage thrust, thereby adjusting the lift force generated by the HASV substructure, which is crucial for controlling heave motion stability.
Previous research on HASV stability control primarily relied on either physical model testing or mathematical modeling. While physical model testing is comprehensive, it is often prohibitively expensive and time-consuming. In contrast, mathematical models, though efficient, require significant simplifications, frequently failing to fully capture complex physical processes, especially those with strong free surface effects. Given the HASV���s limited stability and pronounced free surface effects, there is an urgent need for a more effective and practical approach to investigate and optimize the PID control system. Addressing this need, the study proposes a more accurate Unsteady Reynolds-Averaged Navier-Stokes (URANS) CFD-based control investigation approach. This approach integrates a PID controller into the URANS CFD model, combining the detailed analysis capabilities of CFD with the precision of PID control. This integration ensures that the performance of the proposed control system can be precisely investigated and optimized under different diverse operational scenarios.
This study first starts with the CFD-based hydrodynamic performance analysis of a 2D dual hydrofoils with different configuration and generated a dataset, the dataset is then used to train an Artificial Neural Network (ANN) in order to use the ANN to interpolate within the interesting range and generate a finer resolution results. This analysis helps to have a basic understanding of how the wing and tail can interact with each other and laying the ground for the design of the submerged portion (substructure) of the HASV. Later, this study continues with a scaled-down experimental setup and procedure designed to test the hydrodynamic characteristics of the HASV���s substructure. This experimental study resulted in an understanding of the drag and lift behavior of the substructure, which is be used in the validation of the 3D CFD model. Then, this study continues to use the validated 3D CFD model as a tool to apply the CFD-based control investigation approach, mentioned above, to optimize the performance of the PID controller for regulating the HASV���s roll, pitch and heave motion. Then the effectiveness of the optimized control system on these three DOFs is tested using the CFD-based control investigation approach under different loading scenarios (calm water and waves)
Analytic and Semi-Analytic Calculations for Color Glass in the Weak Field Limit
No full textThe classical field approximation for color glass condensate can be solved using numerical methods and recursive analytic series solutions. The recursive analytic solution is known to have a resummation in Fourier space in the so called weak field limit. Based in this limit, the proper spacetime dependence of quantities related to the gluon two point function are derived. Namely, the gluon energy momentum tensor and corresponding angular momentum tensor, the initial motion of the nuclei after the collision, and the isotropic momentum broadening coefficient are computed.
The McLerran-Venugopalan model is one realization of color glass condensate to which our calculations can be applied. In many cases it can be used to obtain closed analytic expressions, however they are susceptible to UV and IR divergences. An alternative model which maintains UV regularity and softens the IR divergence is thus proposed. The UV region in this new model is regulated by accounting for local charge correlations in the transverse plane. The leading IR divergence is cured by enforcing global color neutrality. Analytic expressions are obtainable in this new model in the form of infinite series.
Novel insights from this work include an analytic understanding of the full time evolution of important physical quantities like energy density, pressure, and momentum broadening, including their late-time behavior; a scheme to systematically include non-constant color charge densities needed to compute realistic nuclei; a numerical understanding of the deceleration of nuclei in collisions, and (for the first time) a calculation of the transverse motion of nuclei
Investigation on Wellbore Cement Integrity During Carbon Capture and Storage (CCS) and Underground Hydrogen Storage (UHS)
No full textThe interactions between hydrogen and carbon dioxide (CO2) with wellbore cement are not fully understood, raising concerns about potential degradation and failure of cement barriers during carbon capture and storage (CCS) and underground hydrogen storage (UHS). This study offers an in-depth analysis of the geochemical, petrophysical, and geo-mechanical properties of cement before and after exposure to hydrogen and CO2. In this study, the cement samples were saturated in 30,000 ppm brine and exposed to the different gases at a pressure of 500 psi and temperature of 50 C for 30 days. In the hydrogen experiment, a notable chemical alteration within the cement matrix was observed, marked by a 50% increase in brownmillerite and a 70% decrease in ettringite. Computed tomography (CT) scans revealed both diminished and clogged pores, along with areas of denser material precipitation. Correspondingly, porosity and permeability measurements showed decreases of 2% and 40%, respectively, while compressive strength and Young's modulus experienced increases of 35% and 6%. The exposure of the cement to CO2 showed significant mineralogical changes, with calcite appearing, constituting 8.7% of the mineral composition, and a complete depletion of alite, signaling extensive carbonation. CT scans highlighted a substantial reduction in pore size and sealed fractures due to calcite precipitation, dramatically affecting porosity and permeability, which decreased by 98% and 87%, respectively. Moreover, the mechanical properties saw remarkable improvements, with compressive strength and Young's modulus increasing by 126% and 161%.
This research is a first of its kind, providing a comprehensive characterization of cement samples before and after exposure to hydrogen, and comparing the results with that of CO2 exposure at the same experimental conditions. The methodological and detailed experimental and analysis approach provided a clear understanding of the interrelationship between the petrophysical, geochemical, and geomechanical impact of exposing the fluids to cement. The findings indicate that in the absence of cyclic and confining stresses, hydrogen and CO2 will not degrade the strength of the cement but, in some cases, could offer healing of fractures and microcannulas if present. The reduction in porosity and permeability of the samples suggests that losses will be reduced when the cement is exposed to hydrogen or CO2
Investigating Vaccinia Virus D10 and Its Homologs
No full textRNA decapping is a fundamental step in eukaryotic mRNA metabolism facilitating the regulation of gene expression by initiating mRNA decay or translational repression. Poxviruses and other nucleocytoplasmic large DNA viruses (NCLDV) encode mRNA decapping enzymes to modulate host and viral RNA levels during infection. The decapping activity is catalyzed by the nudix motif in the protein, which removes the 5��� end m7G cap structure of eukaryotic mRNA by hydrolysis. The prototype poxvirus, vaccinia virus (VACV), encodes two mRNA decapping enzymes: D9 and D10. Previous research has demonstrated the importance of these enzymes by showing a reduction in viral replication when the nudix motif is disabled by mutating key amino acids. Our lab recently showed that VACV D10 colocalizes with mitochondria and that colocalization is also required for VACV replication, hinting at important regulatory mechanisms for D10���s decapping function. Here, we characterized a recombinant VACV with both D9 and D10 knocked out (v���D9���D10). We compared the viral replication dynamics and plaque sizes between v���D9���D10 and the nudix mutant virus (vD9muD10mu). We found that v���D9���D10 showed a significant decrease in both plaque size and viral replication as compared to vD9muD10mu. This result suggests critical regulatory mechanisms of D9/D10 decapping activity that are required for efficient VACV replication. The v���D9���D10 recombinant virus was then used to investigate the ability of D10 homologs to compensate for the loss of D9 and D10. Our findings suggest that the ability of mRNA decapping enzymes to compensate for lack of D10 is unlikely to correlate to the overall sequence similarity, suggesting a more complex regulation mechanism of decapping enzyme���s functions. Additionally, investigation into structural homology led to the discovery that the mitochondrial localization motif recently identified in D10 is structurally conserved in many of the tested homologs. These findings also indicate the possibility that decapping enzymes homologous to D10 may also possess unique functions which aid in their effectiveness
An Innovative Algorithm for Assessing Instance Segmentation in Autofluorescence Microscopy Images
No full textNumerous methods have been created to segment individual cells in microscopy images, highlighting the need for an effective way to evaluate segmented results. Traditionally, the comparison of segmented images with their corresponding ground-truth images is conducted on a pixel-by-pixel basis. However, this approach often overlooks the misallocation of pixels between adjacent objects. In response, we introduce a per-object segmentation evaluation algorithm (POSEA), which assesses the accuracy of segmentation for each object in comparison to a ground truth image. The efficacy of POSEA is validated through the analysis of precision, recall, and f-measure scores, contrasting these with those derived from traditional pixel-based assessments across simulated and segmented fluorescence microscopy images of three distinct cell types. Notably, POSEA identifies a higher rate of segmentation errors due to its accurate recognition of pixels misattributed to adjacent objects. As a result, POSEA offers precise metrics for evaluating the segmentation of adjacent objects, proving its effectiveness for evaluating segmentation algorithms for autofluorescence microscopy images
Art (Spaces) Imitates Life? An Exploration of Arts-Centered Spaces and Their Degree of Accessibility to Immigrant Communities
No full textThis literature review is designed to answer two questions. First, whether art spaces are welcoming spaces for immigrants? Second, what conditions may prompt immigrants to interact or disengage with art spaces? Literature from cultural geography, sociology of culture, urban studies, race, ethnicity, and migration have demonstrated that institutions such as the art museum have historically been sites of domination (Anderson 2006; Cooks 2011; Lonetree 2012). Despite this, museums have displayed an effort to change, while marginalized communities embody the capacity to partake in placemaking endeavors regardless of these constraints (Hooper-Greenhill 2000; Roberts 2018, 2020; Lipsitz 2011; Cook 2011; Lonetree 2012; Jenkins 2010; Jamal 2010, Espiritu 2010, Maira 2010, Stern et. al. 2010). Moreover, art-spaces have been shown to benefit people in both an individual and communal sense (Grodach 2010, 2011; Eaves 2014; Eisner 2012). At the same time, the literature shows that immigrants tend to prefer more informal or private venues to partake in the consumption or creation of art. Although this is the case, we cannot discern exactly why this dynamic is occurring (Stern et. al 2010). Literature regarding cultural capital and strategic assimilation point to possible theoretical explanations of this dynamic, but further research must be conducted to fully address this discrepancy (Bourdieu 1977; Lamont and Lareau 1988; Lacy 2007). In the completion of this literature review, I also offer suggestions to improve existing art spaces based upon the concepts of the Black Spatial Imaginary and Community Asset Mapping (Lipsitz 2011; Villanueva 2020, 2021)
Ira Greenbaum field notebook: GK6501-GK7000.pdf
No full textBound book, each page corresponds to a karyotype slide data.Data pages for GK6501-GK7000 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
Advancing Iron Catalyzed Three-Component Cross-Coupling Reactions
No full textTransition metal���catalyzed cross-coupling reactions are some of the most widely used methods in chemical synthesis. Notable advantages of iron as a potentially cheaper, more abundant, and a less toxic transition metal catalyst have drawn the interest of our lab, in particular to explore the mechanism of action in three-component radical cross-couplings. In the first project, we explored the difunctionalization of unactivated olefins with alkyl halides and Grignard reagents. The reaction tolerates a wide range of sp^2 hybridized nucleophiles, alkyl halides, and unactivated olefins bearing a diverse range of functional groups.
Our second work highlights iron���s practical application in more elaborate multicomponent cross-couplings including formation and trapping of ��-boryl radicals and allyl alkyl halides for practical synthesis of cyclic fluorous compounds. Incorporating fluorine into drug scaffolds remains of utmost importance in medicinal chemistry since it generally increases lipophilicity, stability, and overall lifetime, and ~20% of drugs on the market contain at least one C-F bond. In that vein, pinacol boronate esters and boronic acids are excellent building blocks due to their reaction efficiency, low cost, and ability to be transformed into many other desired functional groups.
The final research focus is on using a mechanistic-driven approach towards designing new chiral organoiron catalytic species capable of controlling the C-C bond formation with diverse C-centered radicals. To date, there are only three examples of enantioselective iron-catalyzed cross-coupling reactions, and all are limited to the union of only two components. We reported a practical and simple protocol that uses commercially available and inexpensive iron salts in combination with chiral bisphosphine ligands to enable the regio- and enantioselective (up to 91:9) multicomponent cross-coupling of vinyl boronates, (fluoro)alkyl halides, and Grignard reagents. Preliminary mechanistic studies are consistent with rapid formation of ��-boryl radical followed by reversible radical addition to mono-aryl bisphosphine-Fe(II) and subsequent enantioselective inner-sphere reductive elimination. Overall, my research is expected to expand the field of asymmetric iron cross-couplings and have broad implications towards the synthesis of bioactive compounds via the use of alkenes to translocate alkyl radicals, modify their steric and electronic properties, and induce stereocontrol