LOUIS University of Alabama in Huntsville
Not a member yet
8547 research outputs found
Sort by
Evaluation of strain-rate sensitivity of 3K70PW/INF114 woven fiber-reinforced composite material
No full textFiber reinforced composites have seen continued use in aerospace and automotive industries due to their inherent high strength-to-weight ratios, which makes them ideal choices for vehicles where fuel economy is an important design factor. However, it is necessary for structures in these industries to preserve the life and safety of passengers in the event of a crash; thus, crashworthiness of these vehicles must be tested. Many finite element material models for simulating composite materials exist, but few take strain rate effects into account, which is important for accurate modeling of dynamic crash scenarios. LS DYNA MAT_213 is a material model developed to accurately simulate high speed impact loading of composite materials, but it requires inputs of tabulated stress-strain data of materials under high-rate tension, compression, and shear loading for accurate simulation. Currently, there is no generally accepted standardized method for performing high-rate shear tests on fiber reinforced composites, and existing high-rate shear methods typically result in mixed mode loading, rather than deformation and fracture under pure shear conditions. This project proposes a novel method for determining high-rate shear properties of composite materials using a split-Hopkinson bar and a specialized test specimen and fixtures. Quasi-static and dynamic shear tests as well as 0 degree, 90 degree, and 45 degree direction tension and compression tests are conducted on a woven composite laminate with 3K70PW fibers and INF114 resin matrix. The performance of the test method is analyzed and tabulated dynamic stress-strain data for 3K70PW/INF114 are produced for use in MAT_213
Decreasing airway emergencies through use of tracheostomy care checklists and nursing coaching
No full textIn intensive care unit patients, tracheostomy tubes are frequently utilized as an adjunct to facilitate weaning from mechanically-assisted ventilation. Tracheostomy placement represents a high-risk intervention within a high-acuity population where complication rates can range from 10% to 15% and sometimes with life-threatening consequences. Amidst shifts in the nursing workforce, bedside nurses demonstrate reduced hands-on experience in managing tracheostomy care and often lack the knowledge, training, and confidence to prevent or effectively manage airway emergencies. To reinforce hospital-based education and policy, the use of nursing checklists modeled after Kamishibai cards and nursing coaching was explored as a strategy to improve nurses’ knowledge and comfort in caring for patients with high-risk surgical airways. Kamishibai cards function as visual cue cards designed to prompt evidence-based care delivery. This project implemented a tracheostomy-specific checklist, designed as a Kamishibai card, within a neurological/neurosurgical intensive care unit (NCU) and stepdown unit. The checklist was completed by the bedside nurse and reviewed by the shift leader to identify areas requiring additional support or informal coaching. The intervention aimed to reduce the incidence of tracheostomy-related emergencies through enhanced nurse preparedness and structured, real-time education. After project implementation, the incidence rate of tracheostomy emergencies in the NCU dropped from 17.2% to a rate of 9.3% during the six-month study period, resulting in a 46% reduction rate
Heat transfer and aerodynamic losses caused by additively manufactured turbine blades enhanced by micro-machining and chemical polishing
No full textAs turbine engines are pushed to operate at higher temperatures and pressure ratios, turbine blades are forced to interact with more extreme conditions. Additive manufacturing (AM) offers new possibilities for meeting these challenges by allowing the fabrication of complex shapes from advanced materials like GRX-810, an alloy designed to maintain strength and durability at extreme temperatures. However, one of the trade-offs with AM is its inherently rough surface finish, which can vary depending on how the surface is treated after printing. This thesis investigates how different surface treatment methods, including micromachining and chemical polishing, as well as the untreated, as-built surface condition, influence the aerodynamic and thermal performance of additively manufactured GRX-810 turbine blades. To evaluate these effects, a series of tests were carried out in a transonic linear cascade wind tunnel using instrumented AM blades
Mutual coupling reduction techniques in transverse-electric-mode and hybrid-mode microstrip patch antenna arrays
No full textWhen the elements of an antenna array are closely spaced, the electromagnetic coupling between them can distort the radiation patterns of the individual elements and change their input impedances, causing significant degradation in the array’s performance. Numerous mutual coupling reduction methods exist in the current literature, each of which allows array elements to be closely spaced while being well-isolated from each other. This dissertation investigates mutual coupling reduction techniques for microstrip patch antenna arrays utilizing elements that excite the fundamental transverse electric (TE) mode. First, a mutual coupling reduction method inspired by the TE-mode microstrip patch cavity model is proposed for a two-element TE-mode microstrip patch array; this method involves placing a vertically-oriented PEC shorting wall, which is physically achieved using a series of connected shorting vias, between the elements to reduce the propagation of surface waves across the antenna structure. When the elements are spaced edge-to-edge, where is the guided wavelength, a mutual coupling of -53 dB is achieved in practice, successfully validating the full-wave results. Second, a mutual coupling reduction method utilizing the inherent orthogonality between TE and transverse magnetic (TM) modes is proposed for a two-element microstrip patch array, where one patch excites the fundamental TE mode and the other excites the fundamental TM mode; under ideal conditions, the mode orthogonality perfectly facilitates the intrinsic decoupling of the elements. The TE and TM mode boundary conditions are enforced according to the respective TE- and TM-mode microstrip patch cavity models. Full-wave analysis indicates that a mutual coupling of less than -20 dB is achieved when the elements are spaced edge-to-edge. Along with the ability to more closely space the elements via the proposed coupling reduction methods, using TE-mode microstrip patch elements further allows array miniaturization in that a TE-mode microstrip patch occupies significantly less surface area than its TM-mode counterpart. Additionally, this dissertation proposes a microstrip patch antenna with modified boundary conditions that excites the higher order TE20 mode with conical radiation patterns. The full-wave analysis and measured results are in excellent agreement and reemphasize the significant surface area reduction inherent to TE-mode microstrip patches
Investigation of alternative satellite constellation dispersion techniques utilizing momentum exchange tethers
No full textSatellite constellations have become an increasingly significant part of the space industry in recent years with the development and operation of next-generation networks such as Starlink, Iridium NEXT, OneWeb, and others. For these constellations to be established, extensive effort must be made to properly disperse and position each member satellite post-launch, typically involving costly propulsion solutions to properly position each satellite and long waiting periods for proper dispersion. Throughout the history of constellation deployments, standard practices of synchronized continuous-thrust altitude-change maneuvers executed by each satellite have been the norm, typically delaying full system coverage and operability by months after launch. These delays can lead to significant financial, strategic, and scientific setbacks for operators, who typically develop constellations for communications or reconnaissance applications where wide coverage is critical. Improvements to the deployment process in terms of reduced time or mass could lead to significant savings in effort and resources for operators across commercial, academic, and defense oriented system developers. Momentum exchange tethers (METs) offer an alternative means of deployment and are capable of alleviating some of these issues shortly after launch. This research explores design processes for orbits, maneuvers, and MET hardware to seek out improvements in terms of reduced dispersion time and mass to orbit, and acts as a formal introduction to this concept. A wide range of MET-based constellation mission configurations were developed and quantitatively compared against traditional mission configurations, giving insight into the application space where METs may be preferable over the utilization of onboard electric or chemical propulsion. The processes developed here seed a new unique application for MET technology with competitive edge over traditional propulsion systems, as well as new constellation deployment processes which could be applied around Earth and key locations such as the Moon or Mars. If pursued, MET-enabled improvements can have significant impacts on the development and deployment of future constellations, and as a result, space infrastructure as a whole
Innovative Film Cooling Configurations for the Upper Pressure Side of a Transonic Turbine Blade for Improved Tip Thermal Management
No full textDirected assembly of magnetic binary suspensions
Get PDFColloids are particle suspensions in a continuous medium. The particle interactions promote the assembly of structures under the influence of a magnetic field, known as directed-assembly. The magnetic properties and shape anisotropy are relevant features of the particle building blocks to the assembled structures. The dipolar interaction between colloidal particles for directed assembly has been extensively modeled considering spherical particle potentials, which is inaccurate when anisotropic particles are at close range. This research aims to address the problem of quantifying the dipolar interaction between arbitrarily positioned and oriented ellipsoids with different aspect ratios and material properties. We combine the recently developed ellipsoid-dipole model and the orientation parametrization of the orientational space with the unit quaternions to quantify the dipolar interaction energy between arbitrarily positioned and oriented ellipsoids. We implement the dipolar interaction energy using the ellipsoid-dipole model in a Monte Carlo algorithm to simulate the assembly of binary suspensions of paramagnetic spheres and diamagnetic ellipsoids in a two-dimensional confinement. We analyze the assembled structures using pair correlation functions and order parameters of the mixture and the independent components. Our results show that local order and symmetry of the assembled structures are tunable under the influence of a uniform magnetic field when one component of the structure is dilute with respect to the other. We also show tunable assembled structures by changing the medium permeability and relative concentration between particle components. The simulations predict a variety of assembled structures, such as triangular structures of ellipsoids enclosing a sphere, chains of ellipsoids linked by spheres, and isotropic systems. These results indicate potential in customizing the assembled structures by tuning both medium and particle properties in binary colloidal suspensions
Synergizing ground, satellite and numerical weather prediction datasets to derive cloud base properties as used in the Kain-Fritsch convective parameterization
Get PDFCloud base height (CBH) and cloud base vertical velocity (CBVV) are essential parameters for understanding cloud formation, boundary layer evolution, and air exchange between the atmosphere and the boundary layer. CBH is linked to aviation safety and impacting the amount of solar radiation reaching the surface, while CBVV influences cloud development, condensation (droplet formation) and precipitation potential. High CBVV can erode capping inversions and trigger convection. These two parameters are the focus of this dissertation. CBH and maximum CBVV values were derived using a multi-linear regression equation (i.e., generalized linear models (GLM)) for CBH and a random forest model for CBVV, with inputs from the Visible Infrared Imaging Radiometer Suite and the High-Resolution Rapid Refresh numerical weather prediction (NWP) model. Observations from the Doppler lidar (DL) and Automated Surface Observing Systems (ASOS) at 10 stations at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) location provided ground truth. Case dates from 2018-2023 over 102 time periods consisted of shallow cumulus with buoyancy as the primary source of vertical motion. The models were tested over a broad region (2° by 2°), with smaller domains created to assess model performance at different resolutions. The CBH GLM model performed well across all domains, but the random forests CBVV model performance degraded as the domain size decreased due to the limited DL stations (1-3) as some of the higher values of CBVV skewed the results. CBH and CBVV data were subsequently incorporated into the Kain-Fritsch (KF) convective parameterization trigger function, which calculates the potential for deep convection in NWP grids. A temperature perturbation (δT) that is part of the trigger function was derived using both CBH and CBVV. δT values ranged from 1.5 to 7.8 K. Finally, Weather Research and Forecasting model simulations were conducted for two case dates, comparing observed and derived values of CBH, CBVV, and δT against a 3 km resolution simulation using the domain setup across the ARM SGP region. Results show that CBH is accurate (~ 200 m), but CBVV is underestimated by 2-3 ms-1, leading to a 3-5 K underestimation in δT in the KF scheme
Increasing the uptake of arteriovenous fistulas in hemodialysis patients through a patient navigator pathway
No full textInternational research has shown that central venous catheters (CVCs) perform worse than arteriovenous fistulas (AVFs) in critical outcomes. The National Kidney Dialysis Outcomes Quality Initiative (NKDOQI) guidelines discourage using CVCs for chronic hemodialysis (HD) and recommend that fewer than 10% of patients undergoing HD for over 90 days use CVCs. AVFs are considered superior to other vascular access methods, offering better longevity, lower infection risk, and reduced mortality and morbidity in most patients. However, a large Veterans Affairs Medical Center Dialysis clinic reported that over 50% of patients were dialyzed via CVCs since January 2022. A literature review conducted from 2019 to 2023 highlighted the positive impact of patient navigators on the care of patients with chronic kidney disease and kidney failure. Research indicates that patient navigators improve health outcomes by acting as a liaison between patients and the multidisciplinary team, particularly in obtaining permanent vascular access. Their inclusion has been shown to reduce disparities and enhance outcomes in renal care. Before the implementation of a patient navigator service, there were 102 hemodialysis patients at the facility. Of these, 5 had grafts, leaving 97 eligible for the project. Among the remaining patients, 49 (50.5%) used CVCs, and 48 (49.5%) had AVFs, marking the starting AVF rate at 49.5%. After the patient navigator was introduced, the AVF rate increased to 56.7%, reflecting a 14.6% improvement in the CVC-to-AVF conversion rate. Notably, seven patients transitioned from CVCs to AVFs, while no patients switched from AVFs to CVCs. This demonstrates that the patient navigator intervention was successful in improving vascular access outcomes by increasing the AVF rate
Evaluation of a remote blood pressure monitoring program
No full textHypertension is a global health problem that impacts millions of people each year and contributes to cardiovascular disease, stroke, chronic kidney disease, and other conditions. Reducing and maintaining control of hypertension leads to better health outcomes. Patient self-measured blood pressure monitoring, along with co-interventions from the healthcare team, is an evidence-based strategy used to reduce and control hypertension. Through advanced technology, remote blood pressure monitoring programs that allow patients to transmit measurements through the internet to physicians’ offices for review and management of hypertension are more readily available. The synthesis of evidence in this document includes the effectiveness of remote monitoring programs in reducing hypertension, the significance of program evaluations, and the importance of engaging stakeholders. A comprehensive evaluation was conducted on an existing remote blood pressure monitoring program utilized by a nephrology practice. The primary objectives of the program were to improve and maintain control of blood pressure in patients with hypertension. Since implemented, the program had not been evaluated for efficacy. The program evaluation included a review of the processes, and a retrospective review of medical records of 207 subjects who had been enrolled in the program and monitored for at least 6 months. Clinical data, including systolic and diastolic blood pressure measurements at enrollment were compared to values documented at the 6th, 12th, and 18th month intervals. Frequency of patient interactions with nurses, antihypertensive medication adjustments, and patient visits with providers were assessed for relationships with blood pressure outcomes. The Center for Disease Control Program Evaluation was used as the framework to guide this evaluation. Data was analyzed using IBM SPSS and Excel. Findings showed an improvement in blood pressure outcomes and a positive correlation between frequency of antihypertensive medication adjustments and patient visits with the providers. Although no direct relationship was found between frequency of patient interactions with nurses and blood pressure outcomes, the mean number of interactions were 6 per month. Major cardiovascular events that required hospitalization included stroke, chest pain, or hypertensive crisis occurred in 4% of the patients during the first 6 months interval, and in 1% during each subsequent interval