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Multiscale Modeling of Hybrid Structural Composites Enhanced by Aligned Zinc Oxide Nanowires
Get PDFInterfacial properties between fibers and matrix can significantly impact the overall performance of the composite structures. One pioneering approach to enhancing the interfacial properties is growing nanostructures on the fiber. Multiscale modeling is employed in this study to evaluate the interfacial properties of hybrid carbon fiber reinforced polymer (CFRP) composites enhanced by ZnO nanowire (NW) aligned on the fiber surface. Some of the critical information, such as the material properties of ZnO NW, and interfacial properties, cannot be determined easily from the experimental analysis. The hybrid composites have four distinct phases: carbon fiber, interface, aligned ZnO NW/polymer coating, and epoxy matrix. Due to the substantial length-scale differences among the four phases, a multiscale model is developed to analyze the adhesion properties of the hybrid composites. The interfacial properties between the fiber surface and the enhancement layer are investigated at the atomic scale utilizing molecular dynamics (MD) simulations. The accuracy of the molecular model is verified by conducting the tensile analysis for modeling components of the ZnO NW, the graphene sheet, and the cross-linked epoxy units. An atomistic representative volume element (RVE) is developed in which a single ZnO NW is aligned with the carbon fiber and embedded in the cross-linked epoxy.
The traction-separation behavior in both sliding mode (shear separation) and opening mode (normal separation) is evaluated. The cohesive parameters, including the peak traction and adhesion energy, are calculated in each mode. The interfacial properties of the hybrid system are compared with the simulated bare RVE containing fiber and epoxy. MD results showed that the interfacial strength is increased from 485 MPa to 1066 MPa with the ZnO NWs. Additionally, the effect of different parameters on the interfacial properties of the hybrid composite is investigated, including the ZnO NW diameter, ZnO NW length, ZnO NW/graphene crystal twisting angle, loading temperature, and loading rate. Higher interfacial properties are achieved by reducing the diameter of ZnO NW in the enhanced structures. The MD results reveal that increasing the loading temperature leads to a weaker interface. Interfacial properties are initially improved by increasing the loading rate and then becoming rate independent.
Moreover, a multiscale modeling framework is developed to investigate the effect of growing ZnO NWs on the fiber/matrix interface, and the fiber fragmentation mechanism of ZnO NW coated single fiber composite (SFC). Three different chemical groups of Carboxyl (COOH), Carbonyl (CO), and Hydroxyl (OH) with multiple grafting densities are considered as the functional groups. The traction-separation analysis shows that combining the growth of ZnO NW and graphene functionalization significantly enhances the interfacial strength in both opening and sliding mode compared with the bare and non-functionalized CFRP structure. The interface results obtained at the nanoscale are implemented in the cohesive zone model to simulate the interface at the mesoscale. The micro homogenization analysis is performed on an RVE containing ZnO NW grown on the fiber surface and embedded in the matrix to determine the effective material properties of the enhancement layer. The interface and enhancement layer properties are imported in the macroscale hybrid SFC model. The single fiber fragmentation analysis is performed on the macroscale 3D hybrid SFC model employing the UMAT user subroutine and ABAQUS finite element analysis package. The modeling results demonstrate that the load is transferred more efficiently from the matrix to carbon fiber in the ZnO NW coated than in the bare fiber model. The fiber fragmentation is increased by 73% in the hybrid composite structure, indicating the enhanced load-bearing capacity of the SFC by incorporating ZnO NW
Exploratory analyses of patterns of depressive symptomatology and heart-healthy behaviors in cardiac patients
Get PDFThis study explored how depressive symptoms in cardiac patients changed in relation to their performance of health behaviors in the year following completion of cardiac rehabilitation. Extensive graphing and nonparametric tests were used on a longitudinal dataset collected from a cohort of cardiac rehabilitation patients to analyze how patterns of depressive symptomatology trended in relation to patterns of physical activity, diet, and alcohol use over time. An exploratory focus of this study assessed possible sex-based differences in these patterns. Results showed that depressive symptomatology decreased in the year following cardiac rehabilitation independently of diet or alcohol use. Patients who reported higher depressive symptomatology consistently reported lower frequencies of physical activity. Women reported higher depressive symptomatology than men over time. Further studies are warranted to elucidate how male and female cardiac patients differ in their manifestations of depressive symptomatology and the relationships between depression and health behaviors promoted in cardiac rehabilitation
Pursuing an understanding of relationship making within language revitalization: conversations with Indigenous language activists
No full textWe are born into a universe of pre-existing relationships (kinship, ancestral lineage, social and interpersonal, environmental, economic, political, etc.), in addition to the many relationships made intentionally or inadvertently throughout our lives. Within the context of community-based Native American and Indigenous language acquisition and revitalization (LAR), how does the presence or lack of wellness and holism impact the group membersโ abilities to combat community-based internal language endangerment? Pursuing an understanding of Indigenous relationship making in adult language learning groups reveals an interconnected network of relationships amongst mentors, mentees, and peers to maintain and sustain long-term LAR efforts. Through this multivocal experimental ethnography, an autoethonographic narrative is combined with interdisciplinary research and transcultural conversations with long-term Indigenous language activists (champions, warriors, or practitioners). The Indigenous experience across space and time is documented to reveal complexities of LAR life stage knowledge and an analysis of the social efficacy of LAR methodologies for wellness and positive productive social relationships.
This work utilizes Indigenous collaborative research methodologies, poetics, and meaningful visual graphic guides (illustrations) to represent processes of reflection through truth telling, storywork, and meaning making. With over 330 years of combined experience stretched across nearly a century, the Indigenous language activistsโ LAR journeys are discussed to unpack significant social experiences in tandem with LAR methodologies. These experiences reveal ongoing community-based issues which complicate LAR social experiences and outcomes. Ongoing internal issues raise questions about how LAR efforts are interconnected with the creation of healthy Indigenous speech communities, self-care, camaraderie, and a multiplicity of issues causing internal language endangerment. The conversations with Indigenous language activists detail the beginnings of their LAR journeys and analyze issues of access to knowledge, gatekeepers (colonized and assimilated minds), kinship dynamics, language prestige, and lateral violence and oppression, to identify methods they have used to move beyond and resolve such issues.
At the center of this work, is seeking to understand how LAR work is relationship work. After decades of Indigenous endangered language research carried out by scholars across the world, there is now a good understanding of the technical methods of language acquisition. However, posing the questions, what is actually being revitalized and for what future, posits a deeper reflection on the definitions and creation of LAR methodologies which prioritize social wellness and teach to the creation of healthy interpersonal positive and productive relationships amongst Indigenous adult language groups
Monitoring Norman, Oklahoma for temporal variation in SARS-CoV-2 using wastewater during University of Oklahoma football games
Get PDFCoronavirus Disease 2019, more commonly referred to as COVID-19, is the disease caused by the virus Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). It is difficult to then get an accurate measure of cases through typical epidemiological methods such as clinical testing because many people do not know they have the disease. However, SARS-CoV-2 viral particles are often excreted by infected hosts, including those who are asymptomatic, and can be tracked through wastewater in a process called wastewater-based epidemiology (WBE). A problem that complicates WBE is that humans are not static and move in and out of sewer drainages throughout the day. One way to track human movement anonymously is through their cell phones and a software called StreetLightยฎ. Football games at the University of Oklahoma provided an opportunity to combine WBE with StreetLight software to determine if there was an increase in the amount of SARS-CoV-2 in the wastewater due to large events. To determine this, wastewater samples were taken hourly at the City of Norman Water Reclamation Facility (NWRF) beginning on Saturday mornings and ending on Sunday mornings. To compare the amount of SARS-CoV-2 in the wastewater on gamedays was different than other days, composite samples were collected from the NWRF representing weekdays as well as two control Saturdays were selected to sample (one per football season). Finally, population data was collected at hourly intervals on Saturdays to normalize the SARS-CoV-2 concentrations, resulting in a measure we called the viral load per person and make the amount of SARS-CoV-2 in the wastewater comparable between seasons. This study can inform decision makers about hosting large-scale events throughout the rest of the pandemic, as well as during other disease outbreaks. Furthermore, the viral load per person is a novel way of presenting this data that makes comparing sewer drainages possible
Paradise Lost as a Political Warning
Get PDFJohn Milton viewed himself as a prophet and he used his poetry and prose as vehicles for communicating Godโs will to the people of England. This thesis analyzes Paradise Lost having a political message for England. Milton believed language was sacred and that open discourse was the primary target for a tyrant. I will assert that Milton utilizes his epic poem to fulfill his prophetic duty to provide his nation with a method to recognize and expel tyranny
An Investigation of Tricuspid Valve Leaflet Decellularization and Effects on Leaflet Biomechanics and Collagen Architecture
Get PDFThe Tricuspid Heart Valve is composed of three leaflets: the anterior leaflet, posterior leaflet, and septal leaflet. The function of this valve is to open during diastole to allow blood to flow from the atrium to the ventricle, then close during systole to prevent backwards flow of blood, called regurgitation. Valve regurgitation can decrease the effectiveness of the heartbeat and can lead to death over time. Two common heart valve replacements are mechanical heart valves and xenografts. These options have both shown clinical success, however no replacement currently meets the criteria for hemocompatibility, immunological tolerance, and the potential to grow and remodel itself. The decellularized tissue-engineered heart valve (TEHV) may be the key to achieving all of these goals. Decellularization has the potential to remove any immunogenic markers from the tissue while maintaining the complex microstructure that is vital for proper cell differentiation and remodeling. In this study, an H&E staining procedure was optimized for further use in the lab. Nine decellularization procedures with different exposure times to detergent and enzyme solutions were compared to find the optimal procedure. We found that 24-hour exposure to detergent and 12-hour exposure to enzymes was the optimal decellularization procedure for all three leaflets. This optimized decellularization procedure was then used in a biaxial mechanical and collagen microstructural analysis study to determine if the biaxial mechanical characteristics and collagen fiber architecture change as a result of the decellularization treatment. After statistical analysis of several parameters, we found that there were no statistically significant changes from the pre-treatment values to the post-treatment values due to decellularization reagent exposure. These results provide strong evidence that the chosen decellularization procedure is effective at decellularizing the tissue while maintaining the microstructure architecture and mechanical properties of the native leaflet
Symphony for Wind Ensemble
Get PDFSymphony for Wind Ensemble, composed in 2022 by Parker Fritz, is a 25-minute acoustic work for single-part wind ensemble describing the inner feelings and identity realizations of the author as he realizes his dual artistic identity as a performer and composer. The first movement, โAlways Distracted, Never Focused,โ uses evolving drone tone clusters of varying timbres to paint an image of ambiguity towards the authorโs own artistic identity. The second movement, โWith Sadness Comes Acceptance,โ uses rising whole tone scales, modulating chorales, and quickly resolving suspension chains to demonstrate the authorโs conflicting view regarding his artistry, The third and final movement, โRealize and Release,โ is a celebration of the authorโs realized identity as a dual-focused performer and composer. This work considers Henry Brantโs theories of blend and balance as described in his text Textures and Timbres in its orchestration
Comparison of the Measurement Capabilities of CMM and AA-CMM Machines in Flatness Verification
Get PDFManufacturing is among the most important activities contributing to the nationโs economy. Almost everything we see, use, and touch, was made by someone, and now more than ever, quality is paramount across the industry. It is virtually impossible to fabricate perfect parts, and thus it is accepted to have variation in part dimensions specified by acceptable tolerances. For flatness, this tolerance will be the intended smallest variation of material form in a plane of a part. To control those variations and guarantee that the part will function as intended in an assembly, measurement verification must be conducted with specialized metrology equipment. The Coordinate Measuring Machine (CMM) and the Articulated Arm CMM (AA-CMM) are analyzed in this study, to identify their respective advantages and disadvantages in flatness measurement. Therefore, the goal of this pilot study is to identify the measuring limitations of each machine, to propose a methodology to identify appropriate use of each device based on its capabilities. Simple experiments were designed, and flatness measurements made. As expected, it is observed that the CMM performs better than the AA-CMM in flatness measurement. A more detailed statistical analysis must be made in the future to identify the quantitative differences in the use of these instruments, so that the versatility of AA-CMM in Geometry verification could be investigated.
Keywords: CMM, AA-CMM, Laser Point, Metrology device selection, Measurement boundary, Flatness verificatio