SACM - United States of America
Permanent URI for this collectionhttps://drepo.sdl.edu.sa/handle/20.500.14154/9668
Browse
1909 results
Search Results
Item Restricted EXPERIMENTAL INVESTIGATION OF FLOW DYNAMICS IN A 9×9 HELICAL CRUCIFORM FUEL BUNDLE USING TIME-RESOLVED PIV(Saudi Digital Library, 2026) ALLowaimi, Mohammed Habeeb A; Hassan, Yassin AThe Helical Cruciform Fuel (HCF) rods proposed by Lightbridge are intended to enhance the power density of both existing and newly constructed Light Water Reactors (LWRs). Unlike conventional cylindrical rods, the HCF design incorporates axially twisted cruciform-shaped fuel rods. This distinctive geometry provides a self-supporting feature, as the rods make contact and support one another at every 90-degree twist, thereby eliminating the need for spacer grids. In addition, the design improves coolant mixing and allows for a more efficient packing arrangement of the fuel rods, both of which have the potential to increase overall reactor performance. To evaluate these potential advantages, this study proposes a detailed experimental investigation of the flow dynamics within a 9×9 HCF bundle. At present, there is a lack of high-fidelity experimental databases addressing flow behavior in such bundle configurations, especially across multiple flow regimes. The planned investigation will employ a matched index of refraction (MIR) facility in conjunction with Time-Resolved Particle Image Velocimetry (TR-PIV) at two Reynolds numbers: 350, and 7,000. Four measurement planes will be examined: the centered plane, the between-rods plane, the through-rods plane, and the near-wall plane. The analysis will extract first- and second-order flow statistics from the TR-PIV data, including mean velocity distributions, velocity magnitude, turbulent kinetic energy (TKE), root-mean-square velocity fluctuations, vorticity, and Reynolds shear stress. Additionally, power spectral density (PSD) analysis will be performed to evaluate the frequency distribution of streamwise and spanwise velocity fluctuations, enabling identification of dominant spatial frequencies and turbulent flow patterns. The outcome of this work will be a valuable high-quality experimental database for the 9×9 HCF bundle. These results will not only address a significant gap in literature but will also provide essential benchmark data for future computational fluid dynamics (CFD) simulations of advanced nuclear fuel designs36 0Item Restricted Assessment of Dimensional Accuracy, Color Stability, Wear Resistance Against Zirconia, and Relining Tensile Strength in Conventional, Milled, and 3D Printed Complete Dentures: An In Vitro Comparative Analysis(Saudi Digital Library, 2026) Shihata, Hamza; Muftu, AliObjective: This study comprehensively evaluated the properties of complete denture materials fabricated via Stratasys Poly-Jet 3D printing, Ivotion subtractive milling, and conventional heat-polymerized methods. The investigation focused on four key performance aspects: accuracy, resilient denture reline bond strength, color stability, and wear resistance. Materials and Methods: Denture samples were fabricated following each manufacturer's recommended fabrication technique. Accuracy was assessed using root mean square deviation from reference STL files across whole dentures, intaglio surfaces, and teeth regions, with baseline and post-aging measurements. Tensile bond strength of Pac-Dent resilient denture reline on denture bases was measured under standardized load. Color stability denture bases and teeth shade materials was examined by immersion in staining media (toluidine blue, coffee, tea), with color changes quantified using benchtop spectrophotometer per ISO 7491 standards. Wear was simulated over 250,000 cycles against glazed and polished Katana zirconia antagonists, with surface wear quantified using weigh before and after the test. Results: Stratasys 3D-printed dentures demonstrated superior initial accuracy with mean ± SD RMS deviations of 96.8 ± 11.7 µm compared to 584.8 ± 22.4 µm for Ivotion milled (p < 0.001). Tensile bond strength of Pac-Dent soft liner was consistent among groups (conventional: 1.01 ± 0.94 MPa; milled: 0.94 ± 0.94 MPa; 3D-printed: 0.88 ± 0.73 MPa) with no statistical significance (p = 0.781). Ivotion milled bases exhibited the greatest color stability, maintaining ΔE below clinically acceptable thresholds after staining, whereas 3D-printed bases had significantly higher discoloration, particularly with tea (ΔE 6.20 ± 2.60 for pink bases) and with coffee (12.16 ± 4.07 for tooth shade) , p < 0.001). For wear test, conventional denture material experienced significantly greater weight loss than both milled (p = 0.009) and 3D printed (p = 0.032) materials. Conclusion: Printing with Stratasys technology provides Accuracy compared to milling method using this particular workflow. Pac-Dent resilient denture reline material adheres reliably across fabrication types. Ivotion milled denture bases currently offer superior color stability and wear resistance, though 3D printing continues to evolve with improving material properties. These findings provide a comprehensive evaluation to guide clinical material selection and inform the integration of advanced digital denture fabrication workflows.10 0Item Restricted Engineering PEG-b-PPS Bicontinuous Nanospheres for Mycobacterial Lipid Antigen Delivery and CD1-Restricted T Cell Response(Saudi Digital Library, 2026) Almunif, Sultan; Scott, Evan ABicontinuous nanospheres (BCNs) are self-assembled polymer nanostructures with interconnected aqueous channels that enable co-loading of hydrophilic and hydrophobic cargo, making them attractive candidates for vaccine and drug delivery. A key barrier to their broader application has been limited control over BCN size and size distribution. This dissertation establishes a scalable approach to engineer poly(ethylene glycol)-b-poly(propylene sulfide) (PEG-b-PPS) BCNs with tunable size using a multi-inlet vortex mixer (MIVM) flash nanoprecipitation strategy. Structural characterization confirms that bicontinuous internal morphology is maintained across the engineered size range. This work further defines how BCN size and morphology contribute to biological identity, demonstrating that early protein adsorption differs between BCNs and bilayer polymersomes, while in vivo biodistribution is governed predominantly by particle size. These principles are applied to vaccine design by encapsulating the mycobacterial lipid antigen mycolic acid (MA) with defined adjuvant combinations, leveraging BCN multi-loading to evaluate how innate cues shape MA-specific responses. Although Mycobacterium tuberculosis (Mtb) infection elicits immune responses to both protein and lipid antigens, lipid antigen-based vaccination strategies remain underexplored. To address this, PEG-b-PPS BCNs co-encapsulating MA and the protein antigen Ag85B were formulated and benchmarked against Bacillus Calmette-Guérin (BCG) vaccination. MA-Ag85B-BCN vaccination elicits both MA- and Ag85B-specific responses; however, MA-driven T cell activation remains detectable up to 6 months post-vaccination, whereas Ag85B-specific T cell responses were not detected at this time point. A similar long-lasting MA-associated activation pattern is observed after BCG vaccination. Together, these studies connect scalable BCN engineering to biological performance and demonstrate BCN dual-loading as a rational strategy to deliver lipid-protein antigen combinations and shape CD1-restricted T cell responses relevant to tuberculosis vaccination.16 0Item Restricted SAUDI VISION 2030: A SUMMATIVE EVALUATION OF TOURISM (INVESTMENT AND REVENUE)(Saudi Digital Library, 2026) Alotaibi, Nada; Johnny, B. GilleylenSaudi Arabia’s dependence on oil revenues has made its economy vulnerable to fluctuations in global energy markets. To address this challenge, Saudi Vision 2030 was introduced to diversify the economy and strengthen non-oil sectors, particularly tourism. The tourism sector has been identified as a key driver of economic diversification, investment attraction, and employment creation. This study evaluates the performance of Saudi Arabia’s tourism sector within the framework of Vision 2030, focusing on tourism investment and revenue generation. Using a quantitative cross-sectional design, the research analyzes secondary data from 2006 to 2023 on tourist arrivals, tourism investment, tourism spending, and tourism employment. Descriptive and inferential statistical techniques, including time-series analysis, t-tests, and ANOVA, were applied to assess differences before and after the implementation of Vision 2030. The findings indicate significant growth in tourist arrivals, tourism investment, and tourism spending, suggesting that the tourism sector is progressing toward supporting economic diversification and achieving Vision 2030 objectives.12 0Item Restricted CRITICAL IDEOLOGIES OF CYBER DIPLOMACY FRAMEWORK FOR MANAGING FOREIGN AFFAIRS: A SAUDI ARABIAN CONTEXT(Saudi Digital Library, 2025) Alfaqih, Faisal Ibrahim; Mbaziira, Alex VThe rapid advancement of technology has facilitated globalization and interconnectedness, but it has also increased vulnerabilities to cyber threats, affecting businesses, governments, and international relations. Despite significant investments in cybersecurity, Saudi Arabia faces persistent cyber risks, particularly in critical sectors such as energy, finance, and defense, exacerbated by geopolitical tensions and state-sponsored cyberattacks. This study addresses the gap in Saudi Arabia’s foreign affairs strategy by examining the role of cyber diplomacy in enhancing cybersecurity governance and international cooperation. The purpose of this qualitative case study is to explore the relevance, challenges, and priority areas for implementing cyber diplomacy in Saudi Arabia. Guided by security theory, the research answers three key questions: (1) What is cyber diplomacy's relevance in promoting national interests? (2) What challenges hinder its establishment across partner states? (3) What are the priority areas for developing cyber diplomacy in Saudi Arabia? Interviews with 12 cybersecurity professionals from the Ministry of Foreign Affairs (MOFA) and private sectors were analyzed thematically. Findings reveal that cyber diplomacy is crucial for protecting critical infrastructure, fostering economic stability, and enhancing Saudi Arabia’s global influence. However, trust deficits, legal barriers, and geopolitical tensions pose significant challenges. Key recommendations include establishing a National Cyber Diplomacy Strategy, enhancing capacity-building programs, and fostering public-private partnerships. The study concludes that cyber diplomacy is essential for Saudi Arabia’s national security and recommends a multi-stakeholder approach to strengthen cyber resilience and international cooperation. Future research should expand to comparative studies with other Gulf Cooperation Council (GCC) nations to develop regional cyber norms.7 0Item Restricted BUILDING FUTURE LEADERS: CRITICAL FACTORS FOR SUCCESSFUL IMPLEMENTATION OF SUCCESSION PLANNING IN EASTERN HEALTHCARE CLUSTER ADMINISTRATION IN SAUDI ARABIA(Saudi Digital Library, 2026) Alqahtani, Musaad; William, J. RothwellThis study investigated the critical elements shaping the implementation of succession planning within the Saudi Arabian healthcare sector, with a particular to the Eastern Healthcare Cluster (EHC) of Saudi Arabia. Guided by the Flexible Open Systems Model and the Rothwell Seven-Pointed Star Model, the study’s multi-layered approach mapped the organizational elements internally and the external elements with the aid of the various levels (macro, meso, and micro) of the four variables of the PEST approach (politics, economics, societies, and technology), amongst others. Using the Enhanced Critical Incident Technique (ECIT), a qualitative-driven method, the study captured real experiences, narratives, and practice-based examples from 16 senior administrators directly involved in succession-planning efforts. Participants reported 144 critical incidents, categorized as helping Factors (52 incidents, 36.1%), hindering Factors (50 incidents, 34.7%), and wish list Items (42 incidents, 29.2%). The credibility of the findings was ensured through nine Enhanced Critical Incident Technique (ECIT) validation checks, including interview fidelity, independent extraction, participant cross-checking, expert review, and theoretical agreement. Mapping these critical incident categories into the Flexible Open Systems Model by identifying the internal organizational elements that best represented each category. This process surfaced six core components: leadership, strategy, culture, people, processes, and systems—as the foundational domains influencing succession planning implementation. Interestingly, communication emerged as a distinct and essential internal element, expanding the original components and reflecting its central role in the experiences shared by participants. Synthesizing these insights led to the development of the Resilient and Strategic Succession Planning Model (RSSPM), a contextually grounded model designed to strengthen leadership pipeline resilience, organizational readiness, and strategic alignment within Saudi Arabia’s emerging healthcare transformation landscape, aligning with Vision 2030.24 0Item Restricted Impact of the Estrous Cycle on Intestinal Injury in Exertional Heat Stroke in Mice(Saudi Digital Library, 2026) Aldakkan, Ali; Orlando, LaitanoExertional heat stroke (EHS) is the most lethal manifestation of heat illnesses. EHS is characterized by loss of consciousness (LOC), central nervous system (CNS) dysfunction, and hyperthermia during physical exertion. It leads to multiorgan damage. EHS-induced intestinal injury is one of the severe consequences that can facilitate further systemic damage. Through the process of leaky gut, intestinal injury can lead to systemic inflammatory response syndrome (SIRS). To date, a significant gap remains in our understanding of female-specific physiological responses to extreme exercise-heat stress. One contributing factor to this gap is the inability to perform hypothesis-driven research in humans as EHS can be lethal. Therefore, the use of preclinical models in mammals represents a powerful tool to help fill this gap. In female mice, the variability in EHS susceptibility and its further consequences have not been explained. Mice undergo four phases of the estrous cycle (estrus, metestrus, diestrus, and proestrus). The distinct physiological characteristics of estrous phases (estrus and diestrus) may influence the EHS-induced intestinal damage. The overall objective of this project is to investigate phase-dependent injury severity, in both early recovery (30 min, 3 h, and 24 h) and late recovery stages (14 d and 30 d) post-EHS. Knowing that in our model estrus (E) and diestrus (D) showed no differences in hypothermic depth, led us to hypothesize that the level of intestinal damage would follow the same pattern. A total of 79 adult female (E: n = 42; D: n = 37) C57BL/6J mice, aged 16–17 weeks, underwent an exertional heat stroke protocol. Post-EHS, we performed terminal experiments for early and late recovery timepoints. Following data collection and preparation, we evaluated tissue integrity using Chiu scale for early and late recovery timepoints, and intestinal morphometrics 3 h post-EHS. Our analyses of Chiu injury scores from early and late recovery stages demonstrated no differences. Similarly, the morphometric analyses showed no phase-specific differences. The fact that estrus animals showed similar levels of intestinal damage to diestrus, while running significantly longer, suggests that they were relatively more protected, as they tolerated greater thermal and exercise stress before reaching similar result.25 0Item Restricted THE PERCEIVED VALUE OF AMERICAN ENGLISH IN ENGLISH LANGUAGE CLASSES IN SAUDI ARABIA(Saudi Digital Library, 2026) Albishi, Dhafer; Felice, A ColesThis dissertation investigates the perceptions and preferences of Arabic-speaking English as a Second Language (ESL) learners and faculty members in Saudi Arabia regarding General American English (GAE). Situated within the broader sociolinguistic debate on English varieties, the study explores why GAE is consistently prioritized in instruction, how it is reinforced through media exposure, and what implications this has for pedagogy and curriculum design. The research adopts a qualitative design, combining open-ended questionnaires with 20 student participants and semi-structured interviews with an instructor and program coordinator at a Saudi Arabian community college. Data were analyzed thematically, following Braun and Clarke’s framework, to capture both learner perspectives and institutional practices. Findings reveal that GAE dominates learner preferences due to its perceived clarity, accessibility, and prestige, as well as its widespread presence in digital media such as Netflix, YouTube, and TikTok. Students described GAE as “normal,” “easy,” and “modern,” illustrating how emotional reactions and social associations reinforce rational judgments of intelligibility. Faculty perspectives aligned with this preference, emphasizing GAE’s pedagogical simplicity and practical utility for academic and professional success. At the same time, results showed that early starters and students with higher media exposure were more open to dialectal diversity, while late starters relied heavily on GAE as an instructional anchor. Although awareness of World Englishes was limited, both faculty members expressed cautious support for introducing dialectal variation at advanced stages, reflecting a pragmatic but forward-looking pedagogy. These results highlight a dynamic interplay between institutional choices, learner experiences, and global linguistic ideologies, with GAE functioning as both a practical learning model and a symbolic marker of modernity. The study contributes to applied linguistics by demonstrating how localized learner attitudes intersect with global language hierarchies. It recommends a tiered pedagogical approach: establishing GAE as a stable foundation at early stages, then gradually incorporating dialectal awareness to prepare learners for multilingual, multicultural communication. Future research should include longitudinal designs, cross-institutional comparisons, and investigations into the role of media literacy in shaping dialectal awareness.6 0Item Restricted Topologically Associating Domains: At the Crossroads of Genome Structure and Function(Saudi Digital Library, 2024) Almansour, Faisal; Misteli, TomUnderstanding the 3D architecture of the genome is crucial for elucidating its role in gene regulation and expression. The complex organization of the genome within the cell nucleus plays a pivotal role in gene expression. Topologically associating domains (TADs) are a prominent and ubiquitous architectural feature of genomes in higher organisms, defined as genomic regions that interact more frequently with each other than with their neighboring regions. It has been suggested that TADs function to facilitate the interaction of regulatory elements with their target genes located in the same TAD. However, the relationship between the structure of TADs and the function of the genes they contain remains unclear. This thesis explores the relationship between chromatin domain architecture and gene expression by application of single-cell and single-allele imaging approaches. I have developed innovative single-allele, high-throughput imaging assays, combining DNA and RNA fluorescence in situ hybridization (FISH) to simultaneously probe the structure of individual TADs and the transcriptional activity of their genes. My analysis revealed that transcriptional activity at the allele level is independent of TAD boundary pairing. Notably, variations in TAD boundary distances between alleles within the same nucleus did not correlate with gene activity. Moreover, my results show that global transcription inhibition does not alter TAD structure, whereas the degradation of cohesin, a key TAD architectural protein complex, leads to reduced transcriptional activity alongside the loss of TAD boundary interactions. These findings challenge prevailing assumptions about the functional roles of TAD structure. They underscore the complexity of genomic regulation and open avenues for further research on the mechanisms governing gene expression and the potential of targeting genome architecture for therapeutic purposes.25 0Item Restricted ADVANCES IN REAL-TIME AMERICAN SIGN LANGUAGE RECOGNITION SYSTEM USING DEEP LEARNING TECHNIQUES FOR ENHANCED ACCESSIBILITY(Saudi Digital Library, 2026) Alsharif, Bader; Ilyas, MohammadAdvancements in technology have significantly contributed to the development of innovative tools aimed at improving communication and accessibility for individuals with hearing impairments. This dissertation explores various machine learning and deep learning techniques for recognizing American Sign Language (ASL) gestures, focusing on enhancing accessibility and bridging the communication gap between hearing-impaired and hearing individuals. Traditional machine learning models, such as Random Forest, Support Vector Machines (SVM), and K-Nearest Neighbors (KNN), alongside deep learning architectures like AlexNet, ResNet-50, EfficientNet, ConvNeXt, and VisionTransformer, were investigated for their effectiveness. Experiments conducted on an extensive dataset of 87,000 ASL gesture images revealed exceptional recognition accuracy, with ResNet-50 achieving 99.98% and Random Forest reaching 99.55%, while other models performed within a range of 97% to 98%. Building on these findings, an innovative real-time recognition system was developed, integrating computer vision and deep learning techniques. The project initially utilized MediaPipe for precise hand movement tracking and YOLOv8, a state-of-the-art object detection model, to translate ASL gestures into text in real time. A comprehensive dataset of 29,820 annotated images was created to ensure strong generalization across diverse hand positions and lighting conditions. MediaPipe’s hand landmark annotations significantly enhanced input quality, improving the YOLOv8 models training accuracy. In addition, a more advanced framework was later designed that integrates YOLOv11 with MediaPipe for robust real-time ASL alphabet recognition. This system was trained on a large-scale dataset of 130,000 annotated images with custom keypoint-based annotations, enabling the model to capture subtle variations in hand and finger positions. Experimental evaluation demonstrated outstanding performance, achieving a mean Average Precision (mAP@0.5) of 98.2% with minimal latency, confirming its suitability for real-time applications in education, healthcare, and professional environments. Overall, the findings of this dissertation underscore the transformative potential of AI-driven solutions for ASL recognition. By bridging communication gaps through both traditional classification models and real-time deep learning frameworks, this work contributes to fostering inclusivity, accessibility, and independence for individuals with hearing impairments.6 0