Digital Commons Network^™

Development Of Pre-Stressed Cfrp Fatigue Retrofits For Common Steel Bridge Connections, Korey Albert Pough

Graduate Theses and Dissertations

Aging or deterioration of the nation’s bridge infrastructure is a significant issue that requires attention. Causes for much of this deterioration can be attributed to two main factors, 1) corrosion, and 2) metallic fatigue, both of which work together to reduce the strength and serviceability of bridge components over time. In many instances, strengthening of bridge components using localized retrofits offers an economical and fast solution for increasing the longevity of existing steel bridges; however, such retrofits must be resilient to further corrosion and fatigue damage. In this study, a localized retrofit is developed using pre-stressed Carbon Fiber Reinforced Polymer …

Linking Insomnia And Suicide Ideation: The Role Of Socio-Cognitive Mechanisms In Suicide Risk, Melanie Lauren Bozzay

USF Tampa Graduate Theses and Dissertations

Despite what is known about predictors of suicide risk and consequences of insomnia, research has yet to delineate mechanisms that may explain the known relationship between insomnia symptoms and suicide risk. There is some disagreement in the literature regarding whether this relationship could be primarily explained by recent depressive symptoms, or whether there may be other explanatory factors related to sleep deficits. The present study addressed this contention in the literature by examining 1) whether socio-cognitive variables (e.g. fatigue, appraised social problem-solving ability, and hopelessness) explained this insomnia-ideation relationship, and 2) whether these variables contributed some explanatory variance in suicide …

The Relationship Of Spasticity And Impairments In Force Regulation And Neuromuscular Fatigue Post Stroke, Reivian Berrios Barillas

Dissertations (1934 -)

Hyperreflexia that causes muscle spasticity may contribute to limitations in force regulation and walking ability post stroke. Additionally, neuromuscular fatigue may reduce force regulation, which is important because fatigue can assist to strengthen muscles that control walking. Hyperreflexia may be caused by cortical disinhibition that allows Ia afferents to amplify excitatory synaptic inputs to motoneuron pools. Cortical disinhibition is presumably caused by stroke-related motor cortex damage. Although, other excitatory synaptic sources to motoneurons contribute to motor control, hyperreflexia may be one contributor that affects stroke survivors. However, hyperreflexia is reported infrequently to effect force regulation post stroke. The goal was …

A Comparison Of Quality Of Life Between Intense And Non-Intense Treatment For Patients With Acute Myeloid Leukemia And High-Risk Myelodysplastic Syndrome, Sara Marie Tinsley

USF Tampa Graduate Theses and Dissertations

Acute myeloid leukemia (AML) and high-risk myelodysplastic syndrome (MDS) are hematologic malignancies that occur most frequently in the sixth and seventh decades of life. Both disorders are associated with a poor prognosis, with median survival of one year or less. An overall five-year survival rate for both disorders, regardless of treatment, is less than 10%. A primary goal of treatment is to improve quality of life (QOL) because cure is improbable. The purpose of this longitudinal cohort study was to compare QOL between groups, intensive, non-intensive therapy, and supportive care. The sample consisted of 85 patients with high risk MDS …

Electromechanical Coupling Behavior Of Dielectric Elastomer Transducers, Jianyou Zhou

Electronic Thesis and Dissertation Repository

Dielectric elastomer transducers with large deformation, high energy output, light weight and low cost have been drawing great interest from both the research and industry communities, and shown potential for versatile applications in biomimetics, dynamics, robotics and energy harvesting. However, in addition to multiple failure modes such as electrical breakdown, electromechanical instability, loss-of-tension and fatigue, the performance of dielectric elastomer transducers are also strongly influenced by the hyperelastic and viscoelastic properties of the material. Also, the interplay among these material properties and the failure modes is rather difficult to predict. Therefore, in order to provide guidelines for the optimal design …

Effect Of Duration Of Play On Injury Rate In Men's And Women's Ncaa Sport, John Craig Harwood

Electronic Theses and Dissertations

Injury rates increase with added athletic exposures. Mental and physical fatigue is potentially a component of this increase. However, large scale exposure-related injury trends by injury type, sport and sex are scarce. Consequently, the aim of this thesis was to determine whether injury rates are higher later in games and whether these rates vary with respect to sport, injury type and sex. NCAA injury data collected by the Datalys Center for Sports Injury Research and Prevention indicate that relative injury frequency increases in subsequent periods and this increase is uniform across sports. Subsequent period relative injury frequencies were greater in …

Lower Extremity Biomechanics In Individuals With And Without Previous Hamstring Injury, Jessica A. Mutchler

Human Movement Studies & Special Education Theses & Dissertations

Primary risk factors for hamstrings strains such as fatigue, previous injury and strength deficits have been identified in the research, yet re-injury rates remain high among the physically active. Sub-acute analysis of the hip, knee and ankle biomechanics following a hamstrings strain have been largely overlooked and may provide additional insight into re-injury risks. It was the aim of this dissertation to explore long-term adaptations in walking and running tasks following a hamstrings strain, and to develop a hip endurance test that could be used in future studies.

Project one used a cross-sectional study with test-retest design to develop and …

Renal Artery Stent Fatigue Test, Braden Cooper, Munir Eltal, Jennifer Hawthorne, Ashley Schaefer

Mechanical Engineering

In today’s world of medical innovation, regulations and requirements set by organizations such as the Food and Drug Administration (FDA), the International Organization for Standardization (ISO), and ASTM International (American Society for Testing and Materials) can inhibit rapid innovation by demanding rigorous testing of new designs. For arterial stents, the standard is that each design must be tested to simulate 10 years of life in an environment congruent to an in vivo environment. Endologix in Irvine, California develops and manufactures minimally invasive treatments for aortic diseases, with a focus on stent grafts for the treatment of abdominal aortic aneurysms (AAA). …

Lower Extremity Neuromechanics During A Forward-Side Jump Following Functional Fatigue In Patients With Ankle Instability, Hyun Kim

Theses and Dissertations

Ankle instability (AI) and fatigue impair neuromuscular control as well as dynamic joint stability of the lower extremity. No one has comprehensively examined the effects of AI and fatigue on neuromechanics of the lower extremity during a functional activity. Deficits associated with AI and fatigue could be additive in increasing the risk for injury in patients with AI. PURPOSE: To examine the interaction of AI and fatigue on lower extremity muscle activity, kinematic, and kinetic patterns during a forward-side jump. METHODS: 25 AI (23.3 ± 1.9 yrs, 176.5 ± 10.5 cm, 70.9 ± 11.4 kg), and 25 matched control subjects …

Postpartum Depressive Symptoms: A Study Of Influencing Factors And An Intervention For Improvement, Susan Liipfert Shelton

Nursing Dissertations (PhD)

Postpartum Depression (PPD) is diagnosed in nearly 16% of mothers, yet more women may report symptoms of this mood disorder. Research has focused on assessment and intervention for women considered at risk for PPD while women described as low-risk are potentially overlooked. The purposes of the two-phase study were to describe the depressive symptoms among healthy, low-risk women at 4-8 weeks postpartum, determine the influence from personal characteristics, perceived stress, sleep disturbances, and fatigue to depressive symptoms (Phase I), and pilot test a stroller-walking intervention in Phase II. Women who scored above the median score from the Edinburgh Postnatal Depression …

Unified Cohesive Zone Model For Damage Modeling Due To Cyclic Loading, Derek G. Schesser

Open Access Dissertations

In this dissertation a non-Paris law based unified fatigue cohesive zone model (CZM) capable of predicting both fatigue crack initiation and propagation of delamination cracks in composites with or without starter cracks or stress concentrators has been formulated and validated. The fatigue CZM incorporates normal and shear degradation mechanisms for pre-crack-initiation strength degradation, and simple power-laws for post-crack-initiation fatigue damage accumulation with damage rates computed directly from the in situ cohesive traction-separation history. A unique procedure to determine the in situ loading profiles and an efficient cycle jump strategy have also been developed. It has been demonstrated, through direct comparisons …

Modeling Of Environmentally Assisted Fatigue Crack Growth Behavior, Sree Phani Chandar Reddy

Dissertations

The formation of fatigue cracks and their propagation due to cyclic loading in metals have been a concern for more than hundred years. Since fatigue failure were first reported by the railroad industry in 1840s, tremendous progress has been achieved in understanding fatigue behavior of metals. But fatigue damage is still a concern due to its complex dependency on various environmental variable like humidity, temperature, time and corrosive environment. Although numerous theories and models have been proposed in the past, the effects of environment on fatigue crack growth (FCG) is not completely understood. This dissertation aims to shed light on …

Mechanochemical Investigation Of A Glassy Epoxy-Amine Thermoset Subjected To Fatigue, Stephen Finley Foster

Dissertations

Covalent bonds in organic molecules can be produced, altered, and broken through various sources of energy and processes. These include photochemical, thermochemical, chemical, and mechanochemical processes. Polymeric materials derive their physical properties from the time scale of motion, summation of intermolecular forces, and number of chain entanglements and crosslinks. Glassy thermoset polymers experience mechanical fatigue during dynamic stress loading and properties diminish with inevitable material failure at stress levels below the ultimate tensile strength (UTS). Damage modeling has been successful in predicting the number of cycles required to induce failure in a specimen due to stress. However, it does not …

Four Weeks Of Controlled Frequency Breathing Training Reduces Respiratory Muscle Fatigue In Elite College Swimmers., Alex Robert Burtch 1991-

Electronic Theses and Dissertations

Controlled frequency breathing (CFB) is a common swim training modality that involves holding one’s breath for ~12 strokes before taking another breath. We sought to examine the effects of CFB training on reducing respiratory muscle fatigue (RMF). Elite swimmers (n = 25) were divided into either the CFB or a group that breathed regularly, every ~3rd stroke. The training intervention included 16 sessions of 12x50-m repetitions with either breathing pattern. RMF was defined as the drop in maximal inspiratory mouth-pressure (MIP) between rest and 46 seconds after a 200 yard free-style swimming race (~114 seconds). Pooled results demonstrated a reduction …

Thermal Processing And Mechanical Properties Of Beta Phase Titanium Alloys For Biomedical Applications, Ethan Wood

Graduate Theses & Non-Theses

The past few decades have seen an increase in the use of beta titanium alloys as structural biomaterials. Their combination of excellent mechanical properties, corrosion resistance and biocompatibility, along with a lower Young’s modulus than stainless steel, cobalt-chromium and commercially pure titanium make the beta titanium alloys ideal biomaterials. This work evaluates the use of three beta titanium alloys for biomedical applications. Three beta titanium alloys, Ti 15-3-3-3, Ti SP-700 and Ti Beta-C, underwent thermal processing to optimize mechanical properties. The alloys were subjected to tensile testing, hardness testing, fatigue testing, optical microscopy and SEM fracture analysis in order to …

Face Sheet/Core Debonding In Sandwich Composites Under Static And Fatigue Loading, Manjinder Singh Warriach

Wayne State University Dissertations

Delamination growth due to face sheet/core debonding is a major concern due to its inherent weakness in sandwich composites which can be exacerbated due to the presence of flaws. In this research work The primary objective of this research was to characterize the delamination crack growth behavior in E-glass face sheet/polyurethane foam core sandwich composite with pre-existing initial delamination crack at a face sheet/core interface under static and fatigue for mode I and mixed mode loading. For mode I static loading two types of delamination experiments, namely T-peel test and wedge test were implemented to evaluate fracture toughness in polyurethane …

Examining The Impact Of A Fatigue Intervention On Job Performance: A Longitudinal Study Across United States Hospitals, Megan Gregory

Electronic Theses and Dissertations

Fatigue in healthcare providers has been linked to dangerous outcomes for patients, including medical errors, surgical complications, and accidents. Resident physicians, who traditionally work long hours on minimal sleep, are among the most fatigued. In attempt to mitigate the impact of fatigue on resident physician performance and improve patient safety, the Accreditation Council for Graduate Medical Education (ACGME) implemented a fatigue intervention program in 2011 for medical residency programs in the United States. This caused a significant decrease in the number of hours that first-year residents were permitted to work, compared with hours worked by first-year residents in prior years. …

Is Yoga Effective In Reducing Fatigue In Patients With Multiple Sclerosis?, Melissa L. Hessler

PCOM Physician Assistant Studies Student Scholarship

Objective: The objective of this selective EBM review is to determine whether or not the use of yoga helps to improve fatigue in patients with Multiple Sclerosis (MS).

Study Design: Review of three randomized controlled trials (RCTs) published between 2004-current, all in the English language.

Data Sources: Three randomized controlled trials (RCTs), all of which evaluate the effectiveness of yoga compared to a control group that was asked not to change their exercise habits as they pertain to fatigue. All studies were found using PubMed and EBSCOhost.

Outcomes Measured: Each of the three articles analyzed the effects of yoga therapy …

Fatigue Behavior Of Complex Geometries Produced Via Additive Manufacturing, Lena Huynh

Open Access Theses

Advances in additive manufacturing are enabling the design and production of part geometries that have previously been unrealistic and/or economically infeasible. Direct metal laser sintering, in particular, is an additive manufacturing method that is capable of producing parts from high strength and temperature resistant materials including the nickel-based superalloy, Inconel 718, which is the material used in this thesis.

Alternative Fatigue Cracking Resistance Assessment Criteria Of Asphalt Mixtures With Overlay Tester, Alejandro Miramontes

Open Access Theses & Dissertations

The accumulation of damage due to cracking of hot mix asphalt (HMA) layers under repeated loading along with the climatic effects is known as fatigue cracking. The Overlay Tester (OT) has been implemented or considered by several highway agencies as an index to evaluate the cracking susceptibility and resistance to cracking of asphalt mixtures in the laboratory. The performance indicator used to measure the quality of the HMA mixes is the number of cycles that a specimen may resist during the test until the crack appears and fully propagates to the top of the specimen. The repeatability of the number …

Fatigue Crack Growth Of Nps20 Steel Oil Pipe At Varied Orientations, Craig G. L. Taylor

Electronic Theses and Dissertations

Very few studies concerning fatigue of oil pipe have been conducted using full-scale tests. Further, no research is found in open literature concerning fatigue cracks in the longitudinal direction of pipes, despite being deemed more critical. Fatigue crack growth was investigated in NPS 20, API 5L X-70 grade, straight-seam steel oil pipes in the base metal and at the welded joint for various orientations. Specifically, the effect of the welded joint and crack orientation on the fatigue crack growth behaviour relative to a longitudinal crack in the base metal was determined. The fatigue crack growth behaviour of a longitudinal crack …

Cognitive Fatigue: Exploring The Relationship Between The Fatigue Effect And Action Video-Game Experience, James Brooks

Theses: Doctorates and Masters

the effects of cognitive fatigue. Despite this, there remain advantages to regularly playing action video games. In Study 1, VGPs were significantly better at multitasking on the MATB-II compared to the NVGPs. Further, VGPs also demonstrated superior multitasking when driving, as they made significantly fewer traffic violations compared to NVGPs when not fatigued. VGPs demonstrated eye-movements similar to those of expert drivers; however, this did not result in any difference in performance between the two groups. There was also some evidence of a positive effect of video game training, although there was no advantage of one training technique over the …

Relieving Post-Stroke Fatigue Using A Group-Based Educational Training Approach, Catherine E. Emery

Theses and Dissertations

Post-stroke fatigue is a common problem that may limit participation in everyday activities. Emerging evidence suggests that group-based training in fatigue management may be an efficient means of reducing the effects of post-stroke fatigue. This mixed methods, quasi-experimental study proposed to determine whether a group-based educational program could be successful in relieving post-stroke fatigue and improving participation in daily activities. A convenience sample of stroke survivors (n=20) from retirement communities in southeastern PA were invited to participate in the research. Participants were screened for depression, motor and cognitive recovery, and sleep quality. Fatigue was measured using the Fatigue Severity Scale …

A Stress-Diathesis Model Of Depression: Examining Self-Compassion And Savoring, Justin Ford

Electronic Theses and Dissertations

Depression is a prevalent public health problem, with approximately 6.4% of Americans suffering from the condition each year. Emerging adults are especially vulnerable to depression, as approximately 25% of individuals from age 18-25 have reported experiencing at least one depressive episode. Considering the literature is replete with studies examining etiological components of depression, it surprising that few studies have examined the role of intrapersonal resources in the onset and maintenance of depressive symptoms. The current study sought to investigate depression in the context of intrapersonal resources in two important ways. First, the study examined the protective qualities of intrapersonal resources …

The Effects Of Fatigue On Lower Extremity Kinetics And Kinematics In Subjects With Known Ankle Instability, Lindsay E. Clayton

Theses and Dissertations

The goal of this study was to evaluate biomechanical differences between healthy subjects and those with ankle instability during the gradual onset of lower extremity fatigue from a landing activity. An understanding of these differences is needed in order to prevent future injury to or further debilitation in individuals with ankle instability. A functional fatiguing activity was designed to focus fatigue on the quadriceps muscles, as those are the muscles most frequently fatigued during sport. Measures were taken throughout the progression of fatigue with a force plate and a motion tracking system and included vertical ground reaction force and lower …

Investigation Of Low Back And Shoulder Demand During Cardiopulmonary Resuscitation: The Effect Of Different Compression-Ventilation Ratios, Richard Scott Dainty

Theses and Dissertations (Comprehensive)

Background: The current American Heart Association (AHA) standard cardiopulmonary resuscitation (CPR) is performed with a compression-ventilation ratio of 30:2 (standard CPR), meaning 30 compressions are applied to the chest followed by the administration of two breaths to the victim. Some evidence has shown that performing continuous chest compressions rather than standard CPR with breaks in chest compressions for administering breaths, may increase survival rates after cardiac arrest. Cont-CPR has been shown to be very fatiguing in nature, with a significant drop in chest compression force within the first two minutes of CPR. The purpose of this study was to examine …

Degradation And Fatigue Involving Dissipated Processes, Md Liakat Ali

LSU Doctoral Dissertations

Irreversible material degradation due to cyclic mechanical loading is investigated utilizing the concept of thermodynamic entropy, plastic strain energy, and temperature slope measurement. Uniaxial tension-compression and fully-reversed bending fatigue tests are performed over a wide range of loading conditions with metallic and composite materials subject to both constant- and variable-amplitude loading. A methodology is developed for the estimation of the fatigue fracture entropy (FFE) and fatigue toughness of metallic specimens in a rapid fashion. It is found that the FFE and the fatigue toughness of each material tested are within a small band. The value of FFE is found to …