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Characterization Of High Cycle Fatigue And Laser-Aided Machining And Polishing Of Additively Manufactured Materials, Mohammad Masud Parvez

Doctoral Dissertations

“Additive manufacturing (AM) and laser-aided machining and polishing (LAMP) of materials are emerging manufacturing processes both for research and industrial sectors. The AM process can manufacture near-net-shape parts with complex geometries. Meanwhile, the LAMP process integrated with an AM system offers a high processing rate, minimum heat-affected zone, and easily adjustable process parameters during machining and polishing. In mechanical properties characterization of AM metals and alloys, fatigue is a vitally important test method to understand the behavior of materials in cycling loading and unloading circumstances since most mechanical failures of structures are due to fatigue. To characterize AM metal fatigue …

Evaluation Of Recrosslinkable Preformed Particle Gel (Rppg) As A Fluid Loss Control Material During Drilling Operations, Mohamed Saad M. Ahdaya

Doctoral Dissertations

"One of the most intense, expensive, and time-consuming problems during drilling operations is the loss of circulation, which could result in several consequences, including wellbore collapse, fluid inflow, formation damage, environmental issues, and nonproductive time. This research aims to evaluate novel materials that can mitigate lost circulation and overcome the limitation of other materials. In this research, a comprehensive evaluation of a re-crosslinkable preformed particle gel (RPPG) has been conducted to determine the extent to which it can be used to control drilling fluid losses during drilling operations. The RPPG consists of swellable gel particles that can self-crosslink to form …

Synthesis And Process Optimization Of Colloidal Unimolecular Polymer, Cup, Particle Formation, And Its Interfacial Surface Tension Behavior, Ashish Zore

Doctoral Dissertations

"Colloidal Unimolecular Polymer (CUP) particles are 3-9 nm size single-chain polymer nanoparticles that are made from amphiphilic acrylic co-polymers using the process of water reduction. The formation of CUP particles was driven by the polymer-polymer interactions being greater than polymer-solvent interactions as well as the charge-charge repulsion due to the increasing dielectric of the medium. CUPs provide a surfactant or additive-free nanoparticle system that was useful for studying the interfacial behavior of pure aqueous nanoparticles using a maximum bubble pressure tensiometer. The equilibrium surface tension shows a dependence on concentration and the charge density of the CUP particle. The equilibrium …

Determining Thermal Properties Via Parameter Estimation Of A One-Dimensional, Analytical Model, Lauren B. Tomanek

Doctoral Dissertations

“In thermal applications, thermal conductivity is used to predict how well a material conducts heat. The accuracy of the magnitude of the thermal conductivity becomes increasingly essential to optimize part geometry. Thermal conductivity can vary significantly from the nominal value due to post-processing. The ASTM standards available to measure thermal conductivity are challenging to reproduce because of the insulated and prescribed temperature boundary conditions that are needed. The research introduces two new methods for estimating thermal conductivity that deliver the same accuracy as the existing ASTM standards and are easier to implement. The methods account for losses in the heating …

A Three-Dimensional Fully Coupled Hydro-Mechanical Elasto-Plastic Model For Unsaturated Soils With Consideration Of Hysteresis Behavior, Beshoy Sami Moussa Riad

Doctoral Dissertations

"Unsaturated soils are often used as a construction material in transportation infrastructures; in which it is subjected to cyclic traffic loadings and/or seasonal wetting-drying cycles. While mechanical hysteresis is a common feature of soils in general, hydraulic hysteresis is associated with unsaturated soils. Most existing constitutive models paid limited attention to the mechanical and hydraulic hysteresis behavior of unsaturated soils. This research presents a three-dimensional model for unsaturated soils and a chemo mechanical model for saturated soils. The unsaturated soils’ model has the following characteristic features: (a) the hydraulic and mechanical behaviors are fully coupled under 3D conditions; (b) it …

Advanced Materials And Processes For Gas Separation And Storage Applications, Qasim Mohammed Al-Naddaf

Doctoral Dissertations

"Transition to a clean, renewable energy future requires departure from thermally driven separation processes. In that regard, development of new materials that exhibit high adsorption capacity and selectivity, fast kinetics, and long-term durability under multicomponent conditions is becoming attractive for the applications in clean energy. Moreover, novel sorbents and separation systems that can store gases at normal conditions offer a promising approach for stationary or onboard gas storage. Due to the limitations on the surface area and biding energy restrict commercial materials effectiveness as a potential adsorption and storage material. There is significant interest in the properties of hybrid materials …

Processing And Characterization Of Tini-Based Alloys Fabricated By Laser Aided Manufacturing, Yitao Chen

Doctoral Dissertations

"Laser powder-based directed energy deposition (DED) is a major laser aided additive manufacturing (AM) process for metals. It applies laser energy to deposit metal powders to form 3D metal parts. Apart from manufacturing traditional alloys, DED can also be used to develop advanced alloys with the novel idea of elemental powder mixture feedstock. TiNi-based alloy is a type of shape memory alloy (SMA), a smart material with unique shape memory effects. Using laser powder DED to synthesize TiNi-based SMAs from elemental powder mixture can create more possibilities in new compositions and properties. It can also overcome the limitations of conventional …

Use Of Cellular Concrete For Air Convection Embankment To Protect Permafrost Foundation In Cold Regions, Hanli Wu

Doctoral Dissertations

"Crushed-rock air convection embankment (ACE) has been used to mitigate thaw settlement, and pavement distresses caused by climatic extremes in permafrost regions for over three decades. However, the desired crushed rocks needed for ACE are not readily available in many areas of interior Alaska. Burdened by the need to ship suitable rocks to remote locations, the cost of constructing an ACE is often prohibitively high, which prevents its wide use in Alaska. An existing cementitious material, cellular concrete, may provide the solution.

This study intends to systematically characterize the heat transfer patterns of ACE and identify the performance benefits of …

Design And Synthesis Of Purine Based Neuroprotectors And Novel Synthetic Methods For The Trifluoromethylation Of Aldehyde Hydrazones, Puspa Aryal

Doctoral Dissertations

"Purine-derived compounds are widely investigated as cyclin-dependent kinase inhibitors that have broad applications in the design of pharmaceuticals for treating diseases, such as diabetes, atherosclerosis, and cancers. Towards the goal of effective AGE-inhibitors, and neuroprotector compounds we have synthesized a series of novel purine-based triazoles and investigated their neuroprotective effects, using SHSY-3Y human neuroblastoma cell line. Through these studies, we have identified purine-based neuroprotector compounds that favorably modulate oxidative stress induced by the Fenton reaction-generated reactive oxygen species (ROS).

The C(sp²−H)-trifluoromethylation of hydrazones would give access to the αtrifluoromethylated hydrazones that can serve as intermediates in the synthesis …

Groundwater Withdrawal Estimation Using Integrated Remote Sensing Products And Machine Learning, Sayantan Majumdar

Doctoral Dissertations

"The rising demands for water, food, and energy primarily driven by the increasing global population constitute a pressing issue worldwide. Therefore, the water-food-energy nexus plays a substantial role in developing globally applicable sustainable solutions. Recent technological advancements, including the earth observation programs using spaceborne remote sensing platforms, have enabled us to monitor various critical components affecting the globe. Groundwater, which comprises the world's 30% freshwater, is one such key component of the global water resources and supplies nearly half of the global drinking water.

Despite groundwater overdraft in many parts of the world, including the United States (US), there are …

Georgia Southern Magazine, Georgia Southern University

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The Question Is Not “Can Humans Talk?” Or “Can They Suffer?” But “Can They Reason?”, Clive Phillips

Animal Sentience

In their target article, Rowan et al (2022) make a welcome attempt to chart the development of Western progress over the past two hundred years toward formally recognizing that animals feel. They outline the heroic efforts of Compassion in World Farming to gain for animals the status of sentient beings rather than merely human property. A broader view exists, from human prehistory to the present day, in which animals have been (and still are) understood to be sentient by indigenous peoples as well as by some Eastern religions. Growing recognition in the West that animals feel represents a new age …

Industry 4.0 Remanufacturing: A Novel Approach Towards Smart Remanufacturing, Prashansa Ragampeta

Masters Theses

“Smart remanufacturing has become more popular in recent years as a result of its multiple benefits and the growing need for society to encourage a circular economy that leads to sustainability. One of the most common end-of-life (EoL) choices that can lead to a circular economy is remanufacturing. As a result, at the end-of-life stage of a product, it is critical to prioritize this choice over other accessible options because it is the only recovery option that retains the same quality as a new product. This work focuses on the numerous technologies that can aid in the improvement of smart …

A Convolutional Neural Network (Cnn) For Defect Detection Of Additively Manufactured Parts, Musarrat Farzana Rahman

Masters Theses

“Additive manufacturing (AM) is a layer-by-layer deposition process to fabricate parts with complex geometries. The formation of defects within AM components is a major concern for critical structural and cyclic loading applications. Understanding the mechanisms of defect formation and identifying the defects play an important role in improving the product lifecycle. The convolutional neural network (CNN) has been demonstrated to be an effective deep learning tool for automated detection of defects for both conventional and AM processes. A network with optimized parameters including proper data processing and sampling can improve the performance of the architecture. In this study, for the …

Paula W. Jamison, Ph.D., Otr

OJOT Sponsor Profiles

No abstract provided.

Generation 1.5 Students’ Academic Success: The Interrelationship Between Capital Used And Identity Formation, Susan D. Dudley

Theses and Dissertations

As the number of people immigrating to the United States increases, so does the number of generation 1.5 students in K-12 education (Kanno & Cromley, 2013). With more generation 1.5 students graduating from U.S. high schools, more are also matriculating into higher education institutions (Harklau & Siegal, 2009; Kanno & Cromley, 2013; Kanno & Harklau, 2012; Roberge, 2009). While some generation 1.5 students are successful in U.S. higher education, others are not, and the percentage of generation 1.5 students who are successful is disproportionately less than the percentage of those students who have a U.S. heritage culture (Kanno & Harklau, …

Development And Validation Of A Volunteer Adult Literacy Tutor Perception Feedback Scale, Robert Craig

Theses and Dissertations

This exploratory study developed and validated a Volunteer Adult Literacy Tutor Perception Feedback Scale (VALTPFS). The VALTPFS is a self-report questionnaire that measures the perceptions of one-on-one adult literacy tutors about their values, knowledge sharing, and satisfaction. This instrument is designed to assess the perceptions of adults who volunteer to provide literacy instruction to tutees who are U.S. born native English language speaking adults. The theoretical framework used to inform the development of the VALTPFS is the community of practice (CoP). The CoP framework was used to identify subscales from instruments with established psychometric credentials to operationalize the VALTPFS. As …

Splanchnic Oxygenation And Feeding Intolerance In The Very Low Birthweight Infant, Melissa C. Dollings

Theses and Dissertations

SPLANCHNIC OXYGENATION AND FEEDING INTOLERANCE IN THE VERY LOW BIRTHWEIGHT INFANT

By Melissa C. Dollings, Ph.D.

A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at Virginia Commonwealth University

Virginia Commonwealth University, 2022

Major Director: Lisa F. Brown, Ph.D., RN, School of Nursing

Background. Feeding intolerance is common in preterm infants but can be an ominous precursor of necrotizing enterocolitis, a life-threatening gastrointestinal disease. The definition and management of feeding intolerance vary widely. This research examined the relationship

between feeding intolerance, intrauterine factors, extrauterine factors, and intestinal immaturity and circulatory immaturity in the …

Von Willebrand Factor Levels In The Diagnosis Of Von Willebrand Disease: A Systematic Review And Meta-Analysis, Mohamad A. Kalot, Nedaa Husainat, Abdallah El Alayli, Omar Abughanimeh, Osama Diab, Sammy Tayiem, Bader Madoukh, Ahmad Bilal Dimassi, Aref Qureini, Barbara Ameer

School of Medicine Publications

Von Willebrand Disease (VWD) is associated with significant morbidity as a result of excessive mucocutaneous bleeding symptoms. Patients with VWD can experience easy bruising, epistaxis, gastrointestinal and oral cavity bleeding, as well as heavy menstrual bleeding and bleeding after dental work, surgical procedures, and childbirth. Early diagnosis and treatment is important to prevent and treat these symptoms. We systematically reviewed the accuracy of diagnostic tests using different cut-off values of VWF:Ag and platelet-dependent VWF activity assays in the diagnosis of VWD. We searched Cochrane Central, MEDLINE, and EMBASE for eligible studies. Two investigators screened and abstracted data. Risk of bias …

The Examination Of Health Care System Distrust As A Barrier To Utilization And Engagement Of Preventive Services In The Health Care System In Black Emerging Adults, With A Special Focus On Insurance Status And Usual Source Of Care., Alexandra Wynn

Theses and Dissertations

Health care system distrust is a well-known barrier to health utilization and engagement in older African Americans. However, it has not been explored in Black emerging adults, individuals 18- 26. It is important to explore the social and psychological effects of systemic barriers, such as health care system distrust, in this developmental period as emerging adults undergo unique demographic shifts, changes in sense of self, and identity exploration. Due to emerging adulthood being an exploratory and challenging transitionary phase, emerging adults have an increased susceptibility to preventable morbidity and mortality issues and decreased access to important preventive services. Thus, health …

Race, Weight, Gender And The Embodied (Odied, Odied) Consciousness Of Big-Bodied Black Women Educators: A Phenomenological Study, Kendra D. Johnson

Theses and Dissertations

Big-Bodied Black women in the United States have perpetually navigated the veritable dichotomy of being hyper-visible and invisible (Beauboeuf-Lafontant, 2003; Fleetwood, 2001; Strings, 2019). Fat Black female bodies have borne the burden of exaggerated tropes and exploitation throughout history, stripping them of their femininity and humanity and resulting in a unique form of objectification (Strings, 2019). Inconsistent messages about BBWs, their bodies, and their value in society have endured for generations. They have been essential in constructing the controlling images of Black womanhood in the U.S. (Collins, 2000). The controlling images all evoked thoughts about the suitability of Black women …

Supporting The Mental Health Of Black Students: A Framework For Comprehensive School-Based Mental Health Systems, Shenita Williams

Theses and Dissertations

School-based mental health is plagued with two primary challenges: (a) design and (b) service delivery. The design of school-based mental health is often comprised of fragmented, individual programs and services, and the delivery of mental-health services and support are culturally insensitive. The purpose of this Delphi study, grounded in African-centered thought (Afrocentricity), was to identify essential components of a comprehensive school-based mental-health system necessary to adequately address and support the mental health of Black students in K–12 public school settings. Through the cultural lens of Black experts, the needs of Black students along a continuum of mental health was highlighted. …

Intergenerational Transmission Of Alexithymia As A Predictor Of Child Posttraumatic Stress Outcomes During Covid-19, Casey Burton

Theses and Dissertations

The objective of this study was to test the role of parent alexithymia in explaining why some children are functioning relatively well during the COVID-19 pandemic while others are experiencing poor mental health. Participants were 88 U.S. children (M_age = 9.94 years; 54.5% female; 59.1% White) and their parents/caregivers (68.2% female; 59.1% White). Two models were tested: a path model in which the association between parent alexithymia symptoms and child COVID-19-related posttraumatic stress symptoms (PTSS) was mediated by child alexithymia symptoms, and a moderator model in which the association between parent alexithymia symptoms and child PTSS was moderated …

Cover And Contents

Turkish Journal of Biology

No abstract provided.

Additive Manufacturing Of Continuous Carbon Fiber-Reinforced Sic Ceramic Composite With Multiple Fiber Bundles By An Extrusion-Based Technique, Ruoyu Chen, Adam Bratten, Joshua Rittenhouse, Ming-Chuan Leu, Haiming Wen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Due to the high cost, complex preparation process and difficulty in structural design, the traditional methods for carbon fiber reinforced SiC ceramic composite preparation have great limitations. This paper presents a technique for the additive manufacturing multiple continuous carbon fiber bundle-reinforced SiC ceramic composite with core-shell structure using an extrusion-based technique. A conventional nozzle system was modified to print simultaneously a water based SiC paste with continuous carbon fibers. Different levels of binder contents were investigated to optimize the stickiness, viscosity, thixotropy and viscoelasticity of the paste. After sintering, SiC whiskers were generated on the surface of fiber, which is …

Spatial Transformation Of A Layer-To-Layer Control Model For Selective Laser Melting, Xin Wang, Robert G. Landers, Douglas A. Bristow

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Selective Laser Melting (SLM) is an Additive Manufacturing (AM) technique with challenges in its complexity of process parameters and lack of control schemes. Traditionally, people tried time-domain or frequency-domain control methods, but the complexity of the process goes beyond these methods. In this paper, a novel spatial transformation of SLM models is proposed, which transforms the time-domain process into a spatial domain model and, thus, allows for state-space layer-to-layer control methods. In a space domain, this also provides the convenience of modelling laser path changes. Finally, a layer-to-layer Iterative Learning Control (ILC) method is designed and demonstrates the methodology of …

A Qualitative Study Of Emergency Department Delirium Prevention Initiatives, Anita Chary, Shan W Liu, Ilianna Santangelo, Kyler M Godwin, Christopher R Carpenter, Aanand D Naik, Maura Kennedy

Faculty, Staff and Students Publications

BACKGROUND: Delirium is a serious but preventable syndrome of acute brain failure. It affects 15% of patients presenting to emergency care and up to half of hospitalized patients. The emergency department (ED) often represents the entry point for hospital care for older adults and as such is an important site for delirium prevention.

OBJECTIVE: We sought to characterize delirium prevention initiatives in EDs in the United States and Canada.

METHODS: We conducted qualitative interviews with 16 ED administrators representing 14 EDs with delirium prevention initiatives. We used a combined deductive-inductive approach to code responses about involved staff, target patient population, …

Feature Learning For Optimal Control With B-Spline Representations, Vinay Kenny, Sixiong You, Chaoying Pei, Ran Dai

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The paper develops a feature learning-based method to solve optimal control problems using B-splines to approximate the optimal solutions. The feature learning-based optimal control method can quickly generate near-optimal trajectories for general optimal control problems subject to system dynamics and constraints. The steps in the proposed method are as follows: Firstly, by representing the state and control variables with B-spline functions, the optimal control problem is converted into an approximate nonlinear programming (NLP) problem, where parameters of the B-splines are identified as features of the optimal solution. Secondly, for a specific problem with designated inputs, a dataset of the optimal …

The Silent Pandemic: The Impact Of Covid-19 On The Mental Health Of Adolescents Living With Hiv, Florence Anabwani-Richter, Trina Swanson, Sandile Dlamini, Kizito Katulege, Chikabachi Daire, Geeta Singhal

Faculty, Staff and Students Publications

PURPOSE OF REVIEW: The pandemic caused by the coronavirus disease (COVID-19) has resulted in millions of confirmed cases and likely more than six million deaths globally Worldometer (2022). We sought to understand secondary mental effects in adolescents living with HIV (ALHIV) on the African continent caused by lockdowns, school closures, and other restriction measures for infection control. We reviewed the broader literature and conducted 86 retrospective chart reviews of mental health disorders of ALHIV and interventions utilized at a pediatric clinic in Eswatini.

RECENT FINDINGS: ALHIVs are disproportionately affected by mental health disorders. The COVID-19 pandemic has exacerbated adverse mental …