United Arab Emirates University
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INVESTIGATION OF MECHANICAL PERFORMANCE AND METALLURGICAL CHARACTERISTICS OF TITANIUM GRADE 2 TUBE-TO-TUBESHEET JOINTS
No full textTube-to-tubesheet joints, an integral component of shell and tube heat exchangers, are known for their vulnerability to leakage problems at the joint region due to mechanical and chemical factors coupled with fabrication techniques involved in creating these joints. An ideal condition of manufacturing process parameters and geometrical variables required to produce tube-to-tubesheet joints is highly desired. One of the most promising candidate materials to fabricate tube-to-tubesheet joints is titanium or titanium alloys due to their excellent strength and resistance to corrosion. The present study investigates the structural integrity of three categories of Titanium Grade 2 based tube-to-tubesheet joints comprising of welded joints, expanded joints, and welded-expanded joints. The influence of Tungsten inert gas welding process and three expansion percentages (4%, 6%, and 8%) on the mechanical and metallurgical characteristics are studied with the presence of double grooves on the inner wall of the tubesheet. The study focuses on three distinct zones of the tube: the weld zone (WZ), the heat affected zone (HAZ), and the unaffected base material (UBM), which refers to the portion of the tube that was not influenced by thermal or mechanical processes. The results showed that α′-phase was dominant in the weld zone and the heat affected zone with no noticeable signs for β-phase remnants in the mentioned zones. The microstructural analysis revealed a coarsening in the grain structure when moving from the UBM to WZ through the HAZ. It was observed that HCP α-phase crystals transformed into α′-phase crystals post rapid cooling in WZ and HAZ. Additionally, the results of the XRD analysis confirmed the absence of β-phase at the HAZ and WZ due to the indistinguishable diffraction pattern between the base material (α-phase dominant) and the weld (α′-phase dominant). Microstructural analysis on the expanded joints showed a direct relationship between the expansion percentage and the reduction of grain size near the roller expander in the expanded zone, while grains in transition and unexpanded zones experienced an insignificant impact due to expansion at both tube’s surfaces. The macroscopic studies revealed that the minimum leak path of the weld was satisfactorily greater than two-thirds of the tube wall thickness, or 1.02 mm. The tube pull-out test showed that the tube pull-out loads were greater than the maximum allowableaxial load for all the cases considered, verifying that every joint manufactured for this project was mechanically sound under axial loading conditions. Moreover, the weld region was found to be the hardest region in Vicker\u27s hardness test due to the dominance of the α′-phase, with a maximum hardness of 173.6 HV, and all measured hardness values in the weld region, tubesheet base material, heat affected zones, and tube materials were found to be below the maximum allowable limit. In conclusion, the integration of welding and expansion techniques for Titanium Grade 2 tube-to-tubesheet joints led to a reliable joint design exhibiting superior mechanical performance, refined microstructure, and safe leak-tight characteristics suitable for critical heat exchanger applications
SULFURIZED SERPENTINE AND PEROVSKITE ASSISTED GRAPHITIC CARBON NITRIDE NANOCOMPOSITES FOR PHOTOCATALYTIC GREEN HYDROGEN PRODUCTION
No full textGreen hydrogen production has received great attention in recent years as a solution to mitigate greenhouse gas emissions resulted by burning fossil fuels. This thesis focuses on development of photocatalytic water splitting green hydrogen production under visible light irradiation of g-C3N4 based sulfurized naturally occurring serpentine rock and oxysulfide perovskite nanocomposites. This work reveals the effect of partial sulfurization of co-catalysts to boost charge generation, charge transfer, and light absorption. The presented work determined the potential of sulfurizing naturally occurring rocks and minerals acting as support and enhanced co-catalysts that exhibit narrower band gaps, with sulfur rich sites for visible light hydrogen production, simultaneously. Moreover, it demonstrated the potential of enhancing photocatalytic green hydrogen production of g-C3N4 once coupled with a partially sulfurized co-catalyst, attributing to the formation of competent heterojunctions with efficient charge separation. Characterization techniques implemented in this study are XRD, FTIR, XPS, SEM, TEM, PL, UV-vis, EIS, CV, and several analysis methods like Tauc plot and Mott-Schottky curve. Photocatalytic water splitting green hydrogen production performance was evaluated through evolved hydrogen yield and apparent quantum efficiency at varying composite loading, varying sacrificial agents, sea water, deionized water, and at prolonged durations for stability evaluation. The photocatalytic hydrogen production was investigated using 2D/2D novel oxysulfide perovskite LaCoOxS3-x ultrathin nanosheets (LaCoOxS3-x/g-C3N4), naturally occurring serpentine (Serp/g-C3N4), and sulfurized naturally occurring serpentine (S-Serp/g-C3N4). The LaCoOxS3-x/g-C3N4 composite exhibited the highest apparent quantum yield of 2.005%, achieving an average hydrogen yield of 132.7 μmol g-1 h-1, surpassing the bare g-C3N4 with 46-fold, while the second-best composite is S-Serp/g-C3N4 with 11.6 μmol g-1 h-1 and 7.7-fold enhancement over bare g-C3N4. This research presents a promising solution for enhancing photocatalytic green hydrogen production of g-C3N4 based composites and initiates new paths in tackling g-C3N4 limitations by coupling with oxysulfide perovskite or sulfurized naturally occurring rocks and minerals
POTENTIAL USE OF WASTE-DERIVED PRODUCTS IN PRODUCING GEOPOLYMER SORBENTS
No full textEnvironmental sustainability and the circular economy are central to addressing global challenges in waste management and water pollution. This study investigates the synthesis and performance of geopolymers derived from industrial wastes, including fly ash, waste glass, silt deposits, and carbide lime, as adsorbents for methylene blue (MB) dye removal from water. Geopolymers were engineered under varying particle sizes, NaOH addition methods, and curing temperatures. Their physicochemical and microstructural properties were thoroughly characterized via scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray fluorescence (XRF), Fourier Transform Infrared Spectroscopy (FTIR), andparticle size analysis (PSA). Among the tested formulations, the sodium silicate–sodium hydroxide geopolymer (GEOPOL1) achieved the highest removal efficiency (RE% \u3e98%) and adsorption capacity (qₘₐₓ ≈ 24.8 mg/g), which can be attributed to its optimal silica–alkali balance, fine particle size, and highly porous network. Notably, geopolymers incorporating industrial waste activators such as carbide lime (GEOPOL2) and waste glass (GEOPOL3) also demonstrated strong performance (qₘₐₓ = 17.03 and 13.32 mg/g, respectively), validating the concept of waste valorization in the context of a circular economy. Silt-based geopolymer (GEOPOL5) provided moderate capacity (qₘₐₓ = 10.67 mg/g), further broadening the scope for by-product utilization. Optimization experiments revealed that particle size and the use of room temperature NaOH solution significantly enhance dye removal, while ambient curing yielded robust performance with reduced energy input. Batch adsorption studies established rapid MB removal with equilibrium reached within 24 hours. Isotherm analysis indicated Langmuir-type monolayer adsorption for GEOPOL1 and GEOPOL2, while Freundlich-type heterogeneous adsorption described GEOPOL3 and GEOPOL5, reflecting the surface properties imparted by waste-derived geopolymers. Kinetic modeling fits best with the pseudo-second-order model for all geopolymers, confirming chemisorption as the dominant mechanism. Post-synthesis washing experiments confirmed the environmental safety and stability of the adsorbents, as indicated by reduced pH and TDS values. Economic and environmental analysis confirmed that substituting conventional activators reduced the carbon footprint by up to 68% and production costs by up to 37%. Collectively, these results demonstrate that waste-derived geopolymers are effective, stable, and sustainable adsorbents for dye removal, contributing to waste valorization and circular economy strategies. This research provides a foundation for the development of cost-effective, scalable, and environmentally responsible solutions for water treatment and industrial waste management
NUTRITIONAL STATUS AND ENDOMYCORRHIZAL ROOT COLONIZATION OF VARIOUS FRUIT TREE SPECIES GROWN IN THE OPEN FIELD IN AL AIN, UAE
No full textDomestic cultivation of fruits can greatly contribute to food security and supply of residents with healthy but highly perishable products. However, in the area of Al Ain, the cultivation of dicotyledonous fruit trees at the commercial scale is relatively uncommon, due to risks associated with the impact of the harsh environmental conditions on plant performance. The present study aimed at investigating to which extent mineral nutrient deficiency is responsible for the poor performance of fruit trees during the warm summer season. A five year old fruit tree plantation at the UAEU Research Farm in Al Foah served as study site. The plantation involved sixteen dicotyledonous and commercially relevant fruit tree species. The youngest fully developed leaves of these plants were sampled and analyzed for concentrations of mineral nutritional elements. In addition, root and soil samples were taken from the plant rooting zone to assess the extent of arbuscular mycorrhiza (AM) fungal root colonization and the number of AM fungal spores in the soil. Results revealed a sufficient supply status with cations and P for most plants, and a moderate to low N nutritional status. Plants of all species were severely Zn deficient, and all sampled citrus species and pomegranate showed deficiency of Mn. Plant species that were best able to maintain adequate nutritional status during the hot summer months were mulberry, sidr, and table grapes, and lime. Micronutrient deficiency was identified as a likely reason for poor performance of fruit trees at the Al Foah site. Evaluation of the plant fertilization and irrigation practices revealed a rather low N, P, and K input via the applied manure, and it is recommended to provide plants with additional mineral or organic fertilizer to improve nutrient supply, especially with N. Further recommended is regular foliar application of chelated Zn, Mn and Ni. The irrigation water supply to plantations of fig, almond, citrus species, pomegranate, grapes, and plums was found to be excessive, potentially leading to nutrient leaching from the irrigation basins, and high carbon footprints. It is recommended to base the irrigation water supply on estimation of the potential evapotranspiration in the future. The analysis of AM fungal root colonization of the fruit trees revealed high AM colonization of mango, mulberry, and citrus species. Other mycotrophic species, such as fig, sidr, and pomegranate, however, were not colonized at all. The previous use of the site for ghaf tree plantation did not encourage AM fungal root colonization in fruit trees grown at the same site. It is possible that AM fungi were introduced to the site with the root bales of the fruit trees at the time of planting. Since AM fungi can greatly enhance plant performance in stressful environments and facilitate acquisition of P and micronutrients, it was recommended to inoculate the nonmycorrhizal fruit trees in Al Foah with a biofertililzer containing AM fungal propagules
VIRTUAL REALITY IN ESL TEACHING AND LEARNING IN A HYBRID LEARNING ENVIRONMENT IN THE UNITED ARAB EMIRATES
No full textThis study examines the impact of Virtual Reality (VR) on the oral proficiency of EFL learners in the UAE context, with exploring the instructors and students’ perspectives on using VR as a language learning tool. The study involved 44 Emirati higher education students enrolled in an English Communications Program divided into a control group using traditional methods, and an experimental group using VR tools for communicative activities. Data collection employed mixed-methods research through questionnaire surveys involving college students and interviews with EFL instructors over a ten-week period. According to the findings, the experimental group demonstrated higher oral proficiency than the control group. To be beneficial for the VR assignment, fewer professionals require more help from learners. Because VR is more motivating, appealing, and less stressful than in-person interactions, university students stated that they have a more favorable opinion of it. He underlined the value of assisting students with speaking practice, confidence building, and teamwork. However, the instructor also needed further training to deal with technical problems, such as connectivity and audio quality. The instructor acknowledged VR\u27s ability for immersive learning but noted that institutional and practical boundaries made its integration challenging. The study indicates that scaffolding, arbitration, and internalization extend Sociocultural Theory (SCT) not only in face-to-face settings but also digitally in immersive environments. It also makes the Situated Learning Theory (SLT), in showing that VR can create an authentic, culturally relevant reference to learning the language, allowing learners to attach to the simulated real-world scenarios. From an academic perspective, the study emphasizes the need to align VR activities with course objectives, provide scaffolding for learners with low efficiency levels, and ensure institutional support for long-term implementation. This study is the first to investigate the use of VR to enhance oral competency among EFL students in the Gulf region, specifically in the UAE higher education. It also offers insights into incorporating immersive technology into EFL courses and fills a knowledge gap on the effect of VR on EFL oral competency in the Gulf higher education settings
DOMESTIC INTER-SECTORIAL NETWORK TOPOLOGICAL EVOLUTION AND INDUSTRIAL POLICY: A COMPREHENSIVE NETWORK ANALYSIS
No full textWhile controversial, industrial policy propose a compelling argument for the government role in stimulating economic growth. The “new industrial policy” approach proposes a shift from a “Why” to “How” should industrial policy be implemented. Building upon this, in line with the increased utilization of network theory in economic research, this research examines network analysis as an econometric diagnostic tool asking, “How network analysis could be utilized in understanding the domestic economy and designing industrial policy?”. The study utilizes country input-output tables to calculate centrality measures corresponding to different connectivity concepts, and explore the dependency between domestic industries. The research demonstrated a three steps method of utilizing network analysis in industrial policy design. First, the study examined domestic industries’ positions and identified misalignments and underutilized industries that could be the focus of industrial policy makers. Then moved toward enriching policy makers’ understanding of the expected evolutionary behavior of each sector within each developmental stage by conducting an independent-samples Kruskal Wallis test. Finally, the research focused on examining the impact of some broad policy economic outcomes on industries’ centrality measures utilizing panel data models. The study contributes to a world-wide ongoing debate, paying special attention to exploring the effect of Economic Openness, in terms of both international trade and Foreign Direct Investment, on the domestic inter-sectorial structure. The initial descriptive analysis of a sample of eight countries has shown that industries have inherited attributes corresponding to their role in the economy. The disposition of an industry centrality value provides a key insight to policy makers in identifying the underutilization of some industries or the over-dependency on others in the domestic economy. While absolute connectivity didn’t show significance across development stages in the Kruskal-Wallis Test, supply and demand connectivity and dependency measures show that that domestic inter-sectorial linkages become more specialized as economies develop. This transition involves early volatility in primary industries and reach a climax in the tertiary sector of developed economies. The panel analysis has shown that the effects of openness and other economic policy outcomes vary across industries and developmental stages. Overall, connectivity is found to be positively associated with net FDI, while industries’ demand-side dependency is negatively associated with trade openness. However, in developing economies, trade openness seems to be associated with greater industries’ demand-side dependency
ENHANCING CLOUD-BASED THREAT DETECTION THROUGH EXPLAINABLE AI: A COMPARATIVE STUDY OF MACHINE LEARNING AND XAI-INTEGRATED MODELS
No full textThe rapid adoption of cloud computing brought about serious security concerns, as cloud infrastructures are constantly exposed to cybersecurity threats such as malware and Distributed Denial of Service attacks. Also, on the other hand, current security methodologies have limitations in identifying new threats accurately. Apart from the fact that ML models are highly efficient in detecting attacks, as ‘black boxes,’ they lack interpretability, impacting trust and adoption within vital cloud environments. This research aims to solve this issue by integrating Explainable Artificial Intelligence practices to help enhance both the accuracy and interpretability of AI systems intended to detect threats in cloud environments. Therefore, the central goal is to develop and test models that can identify threats and explain their decision-making process so that insights are understandable by security analysts. Given the CICIDS2017 dataset where the benchmark dataset for cloud network traffic is publicly available, five ML models, including Linear SVM, XGBoost, Logistic Regression, Neural Network, and Random Forest, were trained and tested. Two XAI practices, SHAP and LIME, were utilized to help interpret model predictions, pointing to the most influential features in detecting threats. The experimental results indicate that the investigated models, when enhanced with XAI, were highly accurate while providing transparent explanations to the feature level for their decisions. More specifically, among the studied models, XGBoost and SHAP demonstrated the best tradeoff between accuracy and interpretability. Therefore, the findings imply that the integration of XAI and conventional ML approaches in cloud threat detection models could help address interpretability and reliability concerns. The methodology, therefore, may aid in building more robust and responsible AI-based cybersecurity solutions intended for modern cloud environments
EXPLORING FAMILY-FRIENDLY POLICIES IN THE UAE
No full textThe Family constitutes the fundamental pillar of societies, fostering stability and driving progress. However, contemporary families in the United Arab Emirates (UAE) face increasing challenges due to the growing participation of women in the labor market. While this shift reflects significant social and economic progress, it simultaneously intensifies the pressures on parents to reconcile professional and family responsibilities. Moreover, the scarcity of family-friendly policies (FFPs) exacerbates these challenges even further. This study explores the lived experiences of working parents with young children in the UAE, examining how existing workplace arrangements facilitate or hinder family engagement. A qualitative research design was employed, using in-depth interviews with parents working in public, semi-governmental, and private entities. Additionally, a review of existing UAE laws and policies was conducted to examine the policies that support work-life balance (WLB) for working parents and identify areas for reform. The analysis reveals that current policies and work arrangements significantly influence parents’ ability to maintain WLB. Findings highlight the need for flexible work structures and consistency in implementing FFPs across sectors. By identifying the policies most valued by parents and highlighting the gaps that persist, this research contributes to a growing body of knowledge on FFPs in the UAE. It emphasizes the importance of developing supportive frameworks that promote both parental well-being and family cohesion, ultimately advancing social stability and sustainable development. The study addresses a critical gap in the literature and provides evidence-based recommendations for enhancing family-friendly workplace practices across sectors
EXPLORING THE IMPACT OF FACULTY–STUDENT INTERACTIONS OUTSIDE THE CLASSROOM ON THE SENSE OF BELONGING, ENGAGEMENT, SELF-CONFIDENCE, AND RETENTION AMONG UNDERGRADUATES IN UAE FEDERAL UNIVERSITIES
No full textThe purpose of this study was to examine the ability of faculty-student interaction (FSI) in influencing students\u27 social and academic outcomes and success. In particular, this study sought to investigate the impact of the informal interactions between faculty members and their students outside the classroom on four student outcomes: sense of belonging (SB), engagement (EG), self-confidence (SC), and retention (RT). The participants were 570 undergraduate students who were at their first- and second-year of study from three different UAE federal higher education institutions. The study employed quantitative research design while utilizing an online survey as the main data collection instrument. For data analysis, both PLS-SEM and multiple machine learning algorithms were used to examine the correlation between the research variables. The findings supported all proposed research hypotheses and demonstrated that FSI has significant positive effects on SB (β = 0.599, p \u3c 0.001), EG (β = 0.666, p \u3c 0.001), SC (β = 0.585, p \u3c 0.001), and RT (β = 0.604, p \u3c 0.001), confirming its central role in influencing student success in UAE higher education. The findings of this study offer valuable insights for federal universities in the UAE, where faculty–student formal and informal engagement play a critical role in students’ success. It also suggests that academic institutions should implement formal policies and effective strategies to support faculty-student interaction outside the classroom and invest in faculty development and student-centered services tailored to the local context of the UAE
تقديم المساعدة أو الإغاثة وحالة الضرورة في القانون الجنائي الإماراتي والمقارن
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This study focuses on the full coverage of all aspects of the act of providing assistance or relief in the UAE Penal Code, as a permissible and new reason, and identifying the adaptation of providing assistance or relief in the comparative law. We cannot understand this reason unless we make some kind of comparison between it and the state of necessity in the UAE and comparative law, whether in terms of the required conditions, or in terms of the reasons for their establishment, or in terms of the scope of their application and the effects resulting from them if they are available. Therefore, this research was divided into two sections: the first relates to the similarities between providing relief and a state of necessity, and the second is devoted to studying the differences between them.
ملخص البحث
تركّز هذه الدراسة على الإحاطة الكاملة بجميع جوانب فعل تقديم المساعدة أو الإغاثة في قانون الجرائم والعقوبات الإماراتي، كسبب مبيح ومستحدث، والتعرف أيضاً على تكييف تقديم المساعدة أو الإغاثة في القانون المقارن. ولا يمكن لنا أن نفهم هذا السبب ما لم نقم بإجراء نوع من المقارنة بينه وبين حالة الضرورة في القانون الإماراتي والمقارن، سواء على صعيد الشروط المطلوبة، أو على صعيد أسباب تكريسهما، أو على صعيد نطاق تطبيقهما والآثار الناجمة عنهما في حال توافرهما. ولذلك تم تقسيم هذا البحث إلى مبحثين: الأول يتعلق بأوجه الشبه بين تقديم الإغاثة وحالة الضرورة، والثاني تمّ تكريسه لدراسة أوجه الاختلاف بينهما