Saudi Cultural Missions Theses & Dissertations
Permanent URI for this communityhttps://drepo.sdl.edu.sa/handle/20.500.14154/10
Browse
5 results
Search Results
Item Restricted Layered Extrusion of engineering Metal Alloys (LEMA) using Semi-Solid Thixotropic Feedstock(The University of Sheffield, 2023-08-31) Alharbi, Abdullah; Mumtaz, KamranAdditive manufacturing (AM) has gained significant attention in low- and medium-volume industries due to its ability to create custom products with complex shapes, design freedom, material savings, and short lead times. While most AM processes focus on thermoplastics, there is increasing interest in metal AM systems, including powder bed fusion processes. However, these methods often involve high acquisition and operating costs, limiting accessibility. To address this, this study focuses on developing and investigating the Layered Extrusion of Engineering Metal Alloys (LEMA) system as a cost-effective alternative metal AM approach. The LEMA system manipulates alloys in the semi-solid thixotropic state. Utilising semi-solid metal slurry in extrusion-based AM can result in metal components with substantially lower operating costs and reduced thermal stresses compared to laser-based method. Experimental work initially conducted (Phase I) using the LEMA system involved in-situ creation of semi-solid thixotropic metallic alloys, particularly focusing on the Zn-Sn binary system, but improvements were made to the LEMA system for the subsequent phase to enhance performance. In Phase II, thermodynamic simulations and thermal analysis have indicated that Zn-40Sn holds promise for semi-solid thixotropic applications. Cold extrusion and heat treatment processes were employed to produce thixotropic feedstock with proper microstructures before being additively manufactured. The 3D printed components were evaluated and the result suggested that the adapted method for semi-solid billets preparation was feasible technique which then helped in a successful printing metallic material. Additionally, printing experiments were conducted to study the effects of major process parameters on the quality of deposited single-layer. It was demonstrated that single layers could be printed under 1.5 mm diameter orifice, extrusion speed of 20 mm/min, substrate moving velocity of 200 mm/min, and extrusion temperature of ≈313 ℃. The optimized printing process parameters from these experiments were then utilized for multilayer printing. It was found that substrate temperature is a key factor for achieving good metallurgical layer bonding at the interface of the printed layers. The research results support LEMA's feasibility as an alternative for the metal additive manufacturing route and lays the groundwork for processing SSMs with higher melting points in the future.4 0Item Restricted The assessment of GDF-15 and GDF-15 glycoforms as diagnostic biomarker for interstitial lung disease(UNiversity College London, 2024) Alharbi, Abdullah; Porter, Joanna; Beatson, RichardBackground: Interstitial lung disease (ILD) is a complex and various condition characterized by inflammation and fibrosis in the lung parenchyma. The identification of novel biomarkers is vital for improving diagnosis, prognosis, and treatment of ILD. Objectives: To investigate the role of GDF-15 as a biomarker for ILD, with a focus on its glycosylation patterns and dietary influences. Methods: We conducted a cross-sectional study of 32 BAL and 111 plasma samples from ILD controls. GDF-15 levels were measured using enzyme-linked immunosorbent assay (ELISA), and glycosylation patterns were analysed using lectin-based assays. Results: GDF-15 levels were significantly elevated in ILD patients compared to non-ILD controls (p < 0.001). We also found that GDF-15 was modified by Neu5Gc, a sialic acid acquired through dietary consumption, which was associated with higher levels of inflammation and fibrosis in ILD patients. Conclusion: Our findings suggest that GDF-15 and its glycoforms, particularly Neu5Gc-modified GDF-15, may serve as novel biomarkers for ILD diagnosis and prognosis. This study highlights the importance of considering dietary influences on disease pathogenesis and the potential for personalized treatment strategies. This study provides new insights into the pathogenesis of ILD and identifies GDF-15 as a promising biomarker for diagnosis and prognosis. The findings have important implications for the development of novel diagnostic and therapeutic strategies for ILD.26 0Item Restricted The Influence of Iron and Lignin on Molecules of the Gastrointestinal Microbiome and Its Effect on the Conjugation of Carbapenem Resistance Plasmids(University of Birmingham, 2022-09) Alharbi, Abdullah; Buckner, MichelleThe gastrointestinal microbiome has acted a reservoir for antibiotic resistance genes by harbouring favourable conditions for the the conjugative transfer of resistance plasmids. Resistance against carbapenems, the last resort β-lactam antibiotics, has been on the rise and is mainly mediated by the spread of carbapenemase-encoding plasmids by Klebsiella pneumoniae. Dietary intake of iron and iron chelators can modulate the metabolic and microbial profile of the gastrointestinal microbiome. This project focused on investigating the influence that molecules produced by the gastrointestinal microbiome might have on the conjugation of carbapenem resistance plasmids in K. pneumoniae in reaction to iron and lignin supplementation. A fluorescence reporter system was used to determine the effect of iron and lignin co-supplementation to an ex-vivo colonic supernatant on the conjugation of an endemic carbapenemase-encoding plasmid called pKp-QIL. This was followed by plating-based conjugation assays which measured the frequency of conjugation of a plasmid from clinical isolate called pCPE16_3 in an iron and lignin co-supplemented ex-vivo colonic supernatant. This project has revealed that lignin has no effect on the conjugation of resistance plasmids in iron- available gastrointestinal microbiome.17 0Item Restricted Knowledge, Attitudes, and Behaviors of School Nurses Regarding Their Role in Childhood Obesity Prevention in Saudi Private Elementary Schools(ProQuest, 2023) Alharbi, Abdullah; Colin, Jessie M.Background: School age children are expected to have a normal body mass index which is commensurate with their age group. The prevalence of childhood obesity and overweight is increasing in alarming rates in developing countries, with the highest rate in the Middle East region. School nurses’ involvement in childhood obesity prevention practices will benefit children and their families in managing the epidemic of childhood obesity. However, there is no research addressing the role of school nurses in Saudi Arabia in preventing and managing childhood obesity. Purpose: The purpose of this qualitative study was to explore the critical factors that influence school nurses’ knowledge, attitudes, and behaviors regarding childhood obesity prevention in Saudi private elementary schools. Philosophical Underpinnings: The grounded theory is based within the constructivist paradigm and has philosophical underpinnings of symbolic interactionism and pragmatism. Methods: This study was conducted using Charmaz's constructivist grounded theory approach. Semi-structured interviews were conducted to collect data from 11 school nurses from private elementary schools in Saudi Arabia. Data from the interviews were analyzed according to Charmaz’s analytical process. Theoretical sampling was used to saturate developed categories. A focus group interview was conducted with three experts in the research topic to confirm the generated theory. Results: A conceptual theoretical framework was developed from the rich data collected from the research participants. Three categories (Struggling, Avoiding, Competing Priorities) and a core category (Lacking Support) emerged to support the basic social process Jumping Hurdles: A Pathway to Professional Growth. Conclusions: The study findings may be used to guide nursing education, practice, research, and health and public policy. The conceptual theoretical framework developed in this study can help in understanding the critical factors influencing school nurses’ knowledge, attitudes, and behaviors regarding their role on childhood obesity prevention. Understanding these critical factors can help enhancing school nurses’ role in childhood obesity prevention.17 0Item Restricted OPTIMAL MANAGEMENT AND SIZING FOR BATTERY ENERGY STORAGE SYSTEMS FOR GRID APPLICATIONS(University of Denver, 2023-08-03) Alharbi, Abdullah; Gao, David WenzhongBattery energy storage systems (BESSs) play a dominant role in the reliability, resiliency, economics, and operational flexibility of the power grid. As such, the BESS is a promising and reliable green technology for supporting power grid facilities. However, the integration of BESS technology into power projects can be expensive and challenging, both technologically and in terms of regulation compliance. Thus, it is necessary to examine best practices for fully optimizing BESS sizing, operation, and scheduling in the context of benefiting BESS operators and investors by fully exploiting the valuable economic and technical benefits of BESSs. In this research, we identify several factors in regard to BESS's simultaneous participation in the energy arbitration and frequency regulation markets and how certain BESS characteristics must be considered to optimize return on investment and profit for BESS operators/investors. Specifically, we comprehensively investigate and discuss BESS participation in the energy and ancillary services markets using historical PJM data and by utilizing new sizing and management models to overcome the current challenges involved with integrating BESSs into the power grid. Planning models are developed to determine the optimal values for a microgrid-integrated BESS in terms of power rating, energy rating, and reserved capacity when the microgrid in question participates in the PJM frequency regulation and energy markets. The integrated, optimally-sized BESS seeks to minimize fuel consumption from thermal units in the microgrid and to capture renewable energy to then be traded in the grid market. Furthermore, a novel MILP-optimization methodology is developed and proposed to optimally size and operate a grid-scale Li-ion BESS that performs stacked services. In this model, the state of charge after discharging constrains the BESS's operation. The model considers BESS degradation costs and discharging rate. The model determines the cost function of each of these factors with special attention to the life cycle of a Li-ion BESS. Our research fills a critical gap in the literature by providing a comprehensive approach to the optimal sizing and management of BESSs while considering various uncertainties, contributing to the sustainable integration and operation of BESSs in power grid facilities. Moreover, we investigated the size of BESS while considering uncertainties in both market frequency and energy, BESS cost, and the Automatic Generation Control (AGC) signal. Additionally, a sensitivity analysis was applied to assess BESS efficiency. Thus, a comprehensive sizing model was considered in order to observe the effects of these uncertainty parameters on the size of the BESS. For BESS management, a scheduling model to operate a BESS performing stacked grid services simultaneously is developed. This model aims to maximize the economic return on investment of the BESS while also prolonging its lifespan. The BESS operational control methodology is simulated and solved using MILP. The approach is designed to maximize BESS revenue by optimally bidding in several markets. Finally, we present a viability assessment of a repurposed battery from an electric vehicle (REVB) performing grid applications, in which we evaluate how economical REVBs can be for providing frequency regulation and energy arbitrage. A 1-year planning model for REVBs is applied to compare an REVB BESS with a BESS with new batteries with consideration of a number of factors, including capital cost. In conjunction with this examination of REVBs, we also investigate the cost and lifecycles of the second life of EV batteries26 0