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Microstructures-Based Constitutive Modelling for Dynamic Strain Aging in Metal Alloys
No full textA Doctor of Philosophy Dissertation in Materials Science and Engineering by Arhum Hassan entitled, “Microstructures-Based Constitutive Modelling for Dynamic Strain Aging in Metal Alloys”, submitted in September 2024. Dissertation advisor is Dr. Farid Abed. Soft copy is available (Dissertation, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Dynamic Strain Aging (DSA) is encountered in some metals at certain combinations of temperatures and strain rates. DSA phenomenon arises due to interactions between mobile dislocations and solute atoms that diffuse around them. This dissertation aims to deepen the understanding of dynamic strain aging in different metals and alloys through a comprehensive approach that incorporates microstructure-based constitutive modeling and finite element (FE) analysis. The constitutive model developed in this study incorporates the effect of increased waiting time that activates DSA. This is achieved by introducing diffusion parameters into the model to formulate an expression that predicts the temperature ranges for the activation of DSA at different strain rates. The framework is based on material-specific activation energy for diffusion and the diffusion constants of impurity/solute atoms, with the increase in strength associated with the concentration of these atoms. The model is validated through comparison with experimental results over a broad temperature range for pure metals and alloys such Niobium, Vanadium and Titanium, C45 steel alloy and MMFX high strength steel at different strain rates (0.0015/s – 0.15/s) and over a wide range of temperatures (298K – 923K). The constitutive model was implemented in the commercially available FE software ABAQUS using a user-defined material subroutine coded as VUMAT. The simulation results were validated using available experimental results, both in the presence and absence of DSA, over a broad range of temperatures (200K – 900K) and strain rates (0.001/s – 2200/s) for all the metals and alloys discussed. Moreover, the FE simulations presented in this dissertation indicate that necking initiates earlier in the presence of DSA. The underlying reason is the increased viscosity due to the increased waiting time, which reduces the material’s ability to deform plastically, leading to early failure. Overall, the developed models contribute to a comprehensive understanding of the metallic response under thermo-mechanical loading scenarios, providing valuable insights into the behaviour of metals and alloys subject to DSA.College of Arts and SciencesMultidisciplinary ProgramsPhD in Materials Science and Engineering (PhD-MSE
INScription: Department of International Studies (INS) Issue #26 (November 28, 2024, Issue 4)
No full textCollege of Arts and SciencesDepartment of International Studie
A comparative life cycle assessment of sewage sludge management alternative
No full textA Master of Science thesis in Civil Engineering by Nisrina Ibrahim Younes entitled, “A comparative life cycle assessment of sewage sludge management alternative”, submitted in May 2024. Thesis advisor is Dr. Md. Maruf Mortula and thesis co-advisor is Dr. Kazi Fattah. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
The Use of Modified Composite Zeolite as A Novel Approach to Dental Hygiene Formulation
No full textA Master of Science thesis in Chemical Engineering by Sumaita Rahman entitled, “The Use of Modified Composite Zeolite as A Novel Approach to Dental Hygiene Formulation”, submitted in May 2024. Thesis advisor is Dr. Taleb Ibrahim and thesis co-advisor is Dr. Sarah Dalibalta. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).The modern era and its advanced technologies have led to a significant change in the way we live and what we eat. This has increased global expenditure in dental procedures and the 4th most expensive disease to treat. Bacillus cereus, Serratia marcescens, Escherichia coli, and Streptococcus pneumoniae have been strongly associated with the causes of oral diseases. Research even shows the adverse effects of the discussed strains outside the oral cavity. Hence, it is urgent to find a solution that is both economically viable and medicinally valuable. The complexation of cationic surfactants and smectite clays has been explored and one example of such a combination is that of Cetylpyridinium chloride (CPC) with montmorillonite. This study focuses on formulating a novel composite of CPC and zeolite, assessing its surface morphology, chemical composition, stability, and investigating the anti-bacterial properties of the composite along with viability with HBEC-5i cells. CPC-Zt-Alg beads have shown 100% bactericidal activity against all the strains tested and 5.9% toxic to HBEC-5i cells making it a promising material to be used in the medical industry with its high anti-bacterial activity and low cytotoxicity.College of EngineeringDepartment of Chemical and Biological EngineeringMaster of Science in Chemical Engineering (MSChE
Sodium Alginate Coated Metal Organic Framework For Near Infrared Triggered Release
No full textA Master of Science thesis in Chemical Engineering by Jubaydah Nasrin entitled, “Sodium Alginate Coated Metal Organic Framework For Near Infrared Triggered Release”, submitted in December 2024. Thesis advisor is Dr. Rana Sabouni. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Researchers are actively exploring novel approaches to administer chemotherapy medications more effectively with fewer adverse side effects. Therein, the use of polymer coated metal-organic frameworks, MOFs, are a viable option for pH and light-responsive nanocarriers in controlled drug delivery due to their distinctive physicochemical characteristics. The polymer coated MOF maximizes the synergistic antitumor impact by combining the benefits of physiological stability, tumor microenvironment pH responsiveness, and high drug encapsulation efficiency while simultaneously transporting drugs to the cancerous cells. In this study, commercially synthesized NH₂-MIL-125(Ti), a titanium-based MOF with a BET surface area of 847 m²/g, was coated with sodium alginate (SA) polymer on the crystal lattice of the nanocomposite after the encapsulation of doxorubicin (DOX). The drug release efficiency of SA/DOX@NH₂-MIL-125(Ti) nanocomposite at two different pH levels of 5.3 and 7.4 was investigated with irradiation of Near-infrared Light (NIR) as an external stimulus. Remarkably, the NH₂-MIL-125(Ti) nanocarrier achieved a high encapsulation efficiency of 94% where the drug release of DOX increased in pH level of 5.3 from 7.7% (control) to 51% (NIR-light), whereas at pH 7.4, 9% released in control and only 39% under NIR-light. Reactive Oxygen Species (ROS) test confirmed that the NH₂-MIL-125(Ti) produces good amount of OH radicals under the NIR radiation which is confirmed by the visible blue colour of the solution mixture and a high absorbance peak at 650 nm. Various characterization tests were also conducted to analyze the material such as FTIR where the stretching vibration of C=O bond of DOX at 1650 cm⁻¹ indicated the successful loading of DOX onto the nanocarrier. SEM results showed that the nanocarrier had coarse granular particle with size around 300 nm. XRD results showed that the NH₂-MIL-125(Ti) has stable and crystalline structure. TGA showed the nanocarrier was stable up to 520°C. Overall, the use of polymer coated MOFs, especially NH₂-MIL-125 (Ti), presents a promising candidate for advancing controlled and effective drug delivery in cancer treatment, offering potential benefits in terms of both efficiency and reduced adverse effects.College of EngineeringDepartment of Chemical and Biological EngineeringMaster of Science in Chemical Engineering (MSChE
Advancements and Modification of 3rd Generation Solar Cells for Hydrogen Production
No full textA Doctor of Philosophy Dissertation in Materials Science and Engineering by Adnan Alashkar entitled, “Advancements and Modification of 3rd Generation Solar Cells for Hydrogen Production”, submitted in September 2024. Dissertation advisor is Dr. Taleb Ibrahim and dissertation co-advisor is Dr. Abdul Hai Alalami. Soft copy is available (Dissertation, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Hydrogen is a clean and versatile energy carrier that can be used as a fuel in a variety of applications. Solar-driven hydrogen production via water electrolysis, utilizing third-generation solar cells, represents a sustainable and carbon-neutral approach to generate hydrogen. These advanced solar cells, namely dye-sensitized solar cells (DSSC) and perovskite solar cells (PSC), are prized for their high efficiency, cost-effectiveness, and potential to support sustainable energy initiatives. In addition, central to water electrolysis technologies are the electrodes catalysing the hydrogen evolution reaction (HER), with platinum (Pt) traditionally regarded for its superior catalytic activity. However, Pt limited availability and high cost hinder widespread deployment in commercial electrolysis systems. In this project, two approaches are examined on the path of enhancing the performance, stability, and cost of solar-driven hydrogen production. In the first approach, third generation solar cells are modified through enhancing the performance and figure of merit of DSSCs via utilizing transparent and conductive electrodes made of copper mesh and replacing metal-based sensitizers with natural dye. Ionic liquids (ILs) are employed as additives for bulk passivation of perovskite films which enhanced the stability and performance of PSCs by increasing the power conversion efficiency of the PSC by 2%. The modified third generation solar cells show great enhancement in the cost and performance of solar-driven hydrogen, where DSSCs and passivated PSCs showed an improved figure of merit by 0.05%/AED and 0.14%/AED, respectively when compared to silicon solar cells. In the second approach, Cu and Ni foams are augmented via adding a graphene layer to enhance the electrochemical kinetics of the HER. Graphene is synthesized and deposited employing the facile ball milling technique, thus reducing the time and cost involved in conventional graphene deposition methods. These modifications showcase promising performance of Cu and Ni foams that is comparable to Pt electrodes but at a reduced cost, highlighting their potential for advancing solar-driven hydrogen production technologies.College of Arts and SciencesMultidisciplinary ProgramsPhD in Materials Science and Engineering (PhD-MSE
INScription: Department of International Studies (INS) Issue #23 (August 29, 2024, Issue 1)
No full textCollege of Arts and SciencesDepartment of International Studie
Incorporating Chatgpt In The Academic Research Process: Avoiding Student Stigmatization
No full textChatGPT, a potent and readily accessible technological tool, has recently raised concerns regarding its potential for fostering plagiarism within educational contexts. With its emergence, academic institutions have begun disseminating cautionary advisories to educators, urging them to incorporate notifications in their syllabi to apprise students that the utilization of this application could impinge upon their academic integrity, potentially resulting in a failing grade for their submitted work. While these apprehensions possess a certain degree of validity, university professors had anticipated that their institutions would furnish them with comprehensive training sessions on the utilization of ChatGPT and its pertinent functionalities for pedagogical purposes. The primary objective of this research is to introduce ChatGPT and elucidate how it can be harnessed to encourage tertiary-level students in the composition and refinement of their academic research papers, thereby aiding them in attaining the prescribed learning outcomes delineated in their respective syllabi and the guidelines governing academic writing courses. Furthermore, rather than resorting to punitive measures and undue stress imposition, educational institutions should endeavor to evince genuine concern for their students' well-being. The author posits that the extent of plagiarism facilitated by ChatGPT is contingent upon the nature of the course in which it is employed. Consequently, course instructors should consider implementing tailored instructional and assessment strategies, which will be expounded upon in this study. The research culminates by offering recommendations for the preservation of students' well-being and the mitigation of distrust.American University of Sharja
The n-Total Graph of a Commutative Ring
No full textA Master of Science thesis in Mathematics by Djamila Ait Elhadi entitled, “The n-Total Graph of a Commutative Ring”, submitted in November 2024. Thesis advisor is Dr. Ayman Badawi. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Let n ≥ 1. This thesis introduces the n-total graph of a commutative ring R. The n-total graph of a commutative ring R, denoted by n ─ T(R), is an undirected simple graph with vertex set R, such that two vertices x; y in R are connected by an edge if xⁿ + yⁿ in Z(R). Note that if n = 1, then the 1-total graph of R is the total graph of R as in [7]. In this thesis, we study some graph properties, for example, connectedness, diameter, and girth, for the graph that we defined.College of Arts and SciencesDepartment of Mathematics and StatisticsMaster of Science in Mathematics (MSMTH
Encapsulation and release of calcein from herceptin-conjugated eLiposomes
No full textAchieving an optimal therapeutic level is crucial in effectively eradicating cancer cells during treatment. However, conventional chemotherapy-associated systemic administration of anticancer agents leads to many side effects. To achieve the desired control over the target site, active targeting of HER2-positive breast cancer cells can be achieved by conjugating liposomal vesicles with Human Epidermal growth factor Receptor 2 (HER2) and inducing release of the encapsulated drug using ultrasound. To further enhance the delivery efficiency, nanoemulsion droplets exhibiting responsiveness to low-frequency ultrasound are encapsulated within these lipid vesicles. In this study, we prepared four different liposomal formulations, namely pegylated liposomes, emulsion liposomes (eLiposomes), HER-conjugated liposomes, and HER-conjugated eLiposomes, each loaded with calcein and subjected to a thorough characterization process. Their sizes, phospholipid concentration, and amount of antibody conjugation were compared and analyzed. Cryogenic transmission electron microscopy was used to confirm the encapsulation of nanoemulsion droplets within the liposomes. The drug-releasing performance of Herceptinconjugated eLiposomes was found to surpass that of other liposomal formulations with a notably higher calcein release and established it as a highly effective nanocarrier. The study showcases the efficacy of calcein-loaded and Herceptin-conjugated eLiposomes, which demonstrate rapid and efficient drug release among other liposomal formulations when subjected to ultrasound. This discovery paves the way for a more targeted, efficient, and humane approach to cancer therapy.Dana Gas Endowed Chair for Chemical EngineeringAmerican University of SharjahSheikh Hamdan Award for Medical SciencesFriends of Cancer Patients (FoCP