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A New Hamiltonian Semi-Analytical Approach to Vibration Analysis of Piezoelectric Multi-Layered Plates
No full textA new Hamiltonian semi-analytical method is established to investigate the free vibration characteristics of piezoelectric multilayered plates. By performing a Legendre Transform, the classical Lagrangian functional is recast into a Hamiltonian one, so that the resulting variational formulation can be expressed in terms of the displacements and electric potential and their transverse stresses and electric displacement dual variables. Within the framework of this Hamiltonian formalism, the in-plane of the piezoelectric multilayered plate is discretized into two-dimensional p-type high-order spectral finite elements while the resulting first-order one dimensional differential system is solved analytically by enforcing the interface continuity constraints. The whole piezoelectric multilayered plate’s dynamic stiffness is then built, from which its circular frequencies are computed with the help of the Wittrick-Williams algorithm. A detailed discussion is provided on the implementation aspects, followed by some numerical examples to assess the robustness, accuracy and effectiveness of the proposed method. The obtained results are verified by comparison with published ones based on conventional approaches
Nanocarriers Responsive to Light—A Review
No full textThe non-specific and minimally selective nature of traditional drug administration methods, along with various other limitations, makes the use of drug delivery systems more favorable. Light-responsive, or light-triggered, drug delivery systems provide more controlled and less invasive treatment approaches, addressing the shortcomings of traditional methods. In this paper, we reviewed studies utilizing light-triggered nanoparticles (NPs) for treating cancer and various other diseases, focusing on photodynamic therapy (PDT) and photothermal therapy (PTT) in both in vivo and in vitro applications. Most of the reviewed studies employed synergistic approaches that combined PDT or PTT with other therapeutic methods to leverage the strengths of both techniques and enhance treatment efficiency or to overcome the individual limitations of each method, which is discussed extensively in this paper.Dana Gas Endowed Chair for Chemical Engineering, American University of Sharjah Faculty Research GrantsSheikh Hamdan Award for Medical SciencesFriends of Cancer Patient
Ultrasonically Triggered Release of Folic Acid-Conjugated Liposomes for Breast Cancer Therapy Within Microfluidic Devices
No full textA Master of Science thesis in Chemical Engineering by Taima Khair Alla AlHazaimeh entitled, “Ultrasonically Triggered Release of Folic Acid-Conjugated Liposomes for Breast Cancer Therapy Within Microfluidic Devices”, submitted in May 2024. Thesis advisor is Dr. Ghaleb Husseini and thesis co-advisor is Dr. Mohamed Abdelgawad. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Cancer, among the deadliest diseases, is characterized by the uncontrolled growth and spread of abnormal cells in the body. Chemotherapy, a widely employed treatment for cancer, specifically targets and eliminates rapidly dividing cells, a key characteristic of cancerous cells. However, this approach also affects numerous healthy cells throughout the body that naturally grow fast, leading to severe side effects due to the lack of precision in chemotherapy. Smart Drug Delivery Systems (SDDSs) comprise the encapsulation of therapeutic drugs inside nanoparticles that can deliver the drug exclusively to the tumor site, resulting in fewer side effects. SDDSs leverage the leaky nature of cancer tumor vasculature, allowing nanoparticles to permeate and accumulate more efficiently at the tumor site. Additionally, SDDSs include functionalizing the surface of the nanocarriers to enhance stealth properties, thereby prolonging the lifespan of nanocarriers within the body. Ligands that are also attached to the nanoparticle surface bind to their corresponding receptors, which are overexpressed on cancer cells, facilitating internalization via the endocytic pathway. Moreover, triggering mechanisms, such as ultrasound in this work, could be incorporated to enhance the release of the encapsulated drug exclusively at the tumor site. However, the translation of smart drug delivery systems to clinical trials is limited by the lack of drug screening systems that can mimic the in vivo environment. To overcome this drawback, microfluidic devices provide a powerful tool that can be introduced for drug screening. In this work, we encapsulate the well-known chemotherapy drug Doxorubicin inside PEGylated liposomes, with folic acid attached to the surface of the liposomes to achieve active targeting. In addition, Low-Frequency Ultrasound (LFUS) is used as a triggering mechanism to induce sonoporation and enhance drug release. The drug's performance is tested on a folic acid receptor-positive cell line (MDA-MB-231) and a folic acid receptor-negative cell line (NIH-3T3) achieved by cell culturing inside microchannels. The in vitro experimental results of this research indicate a significantly increased cellular uptake of the anti-cancer drug encapsulated in targeted liposomes with the receptor-positive cell line and an improved cellular uptake upon exposure to LFUS.College of EngineeringDepartment of Chemical and Biological EngineeringMaster of Science in Chemical Engineering (MSChE
Fuzzy Divergence Weighted Ensemble Clustering With Spectral Learning Based on Random Projections for Big Data
No full textIn many real-world applications, data are described by high-dimensional feature spaces, posing new challenges for current ensemble clustering methods. The goal is to combine sets of base clusters to enhance clustering accuracy, but this makes them susceptible to low quality. However, the reliability of present ensemble clustering in high-dimensional data still needs improvement. In this context, we propose a new fuzzy divergence-weighted ensemble clustering based on random projection and spectral learning. Firstly, random projection (RP) is used to create various dimensional data and find membership matrices via fuzzy c-means (FCM). Secondly, fuzzy partitions of random projections are ranked using entropy-based local weighting along with Kullback-Leibler (KL) divergence to detect any uncertainty. Then it used to evaluate the weight of each cluster. Finally, we create regularized graphs from these membership matrices and use spectral matrices to estimate the affinity matrices of these graphs using fuzzy KL divergence anchor graphs. Subsequently, obtaining the final clustering results is considered as an optimization problem, and the ensemble clustering results are obtained. The experimental results on high-dimensional data demonstrate the efficiency of our method compared to state-of-the-art methods
Microwave-Responsive Metal-Organic Frameworks (MOFs) for Enhanced In Vitro Controlled Release of Doxorubicin
No full textMetal-organic frameworks (MOFs) are excellent candidates for a range of applications because of their numerous advantages, such as high surface area, porosity, and thermal and chemical stability. In this study, microwave (MW) irradiation is used as a novel stimulus in vitro controlled release of Doxorubicin (DOX) from two MOFs, namely Fe-BTC and MIL-53(Al), to enhance drug delivery in cancer therapy. DOX was encapsulated into Fe-BTC and MIL-53(Al) with drug-loading efficiencies of up to 67% for Fe-BTC and 40% for MIL-53(Al). Several characterization tests, including XRD, FTIR, TGA, BET, FE-SEM, and EDX, confirmed both MOF samples’ drug-loading and -release mechanisms. Fe-BTC exhibited a substantial improvement in drug-release efficiency (54%) when exposed to microwave irradiation at pH 7.4 for 50 min, whereas 11% was achieved without the external modality. A similar result was observed at pH 5.3; however, in both cases, the release efficiencies were substantially higher with microwave exposure (40%) than without (6%). In contrast, MIL-53(Al) exhibited greater sensitivity to pH, displaying a higher release rate (66%) after 38 min at pH 5.3 compared to 55% after 50 min at pH 7.4 when subjected to microwave irradiation. These results highlight the potential of both MOFs as highly heat-responsive to thermal stimuli. The results of the MTT assay demonstrated the cell viability across different concentrations of the MOFs after two days of incubation. This suggests that MOFs hold promise as potential candidates for tumor targeting. Additionally, the fact that the cells maintained their viability at different durations of microwave exposure confirms that the latter is a safe modality for triggering drug release from MOFs.American University of SharjahNatural Sciences and Engineering Research Council of Canada (NSERC
Characterization of the dynamic flow response in microfluidic devices
No full textA Master of Science thesis in Mechanical Engineering by Mohammed Elmahdi Elgack entitled, “Characterization of the dynamic flow response in microfluidic devices”, submitted in May 2024. Thesis advisor is Dr. Mohamed Abdelgawad. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Microfluidics, which pertains to liquid manipulation on the microscale, have become an essential tool in many chemical and biological applications during the past two decades. Proper functioning of microfluidic devices requires precise control of the flow inside microchannels which is a challenging task given the unconventional fluid flow phenomena that arise on the microscale. For example, the flow rate-pressure relation in microfluidic devices made of soft material like polydimethylsiloxane (PDMS), is significantly changed by the wall compliance. Moreover, the small volume changes due to liquid compressibility in the case of syringe pump-driven flows can be the same order of magnitude as the liquid volume in narrow sections of the device. This will result in unexpectedly long times to initiate liquid motion, which is known as the “bottleneck effect”. Therefore, the underlying effects of such common situations must be carefully considered. This compressible fluid-structure interaction problem was investigated here with different system parameters that govern the transient times in microchannels. Numerical simulation and experiments were conducted to characterize both compliance and bottlenecking effects in microfluidic devices of different elasticities filled with different liquids. A numerical simulations-based model was created to predict the compliance of thick PDMS microchannels as a direct function of the channel dimensions, and it gave a good fit for data outside of the study range with an error within 4%. This model predicted the dynamic response of microchannels accurately as long as the pressure drop was not high. A less accurate (10% error) pressure-dependent model was created to capture the increase in microchannel compliance due to the non-linear behavior of PDMS dominance under high pressures. Experiments were used to characterize the effect of syringe volume, microchannel resistance, and liquid type on the flow dynamic response caused by the bottleneck effect. When the bottleneck effect was present, the elasticity of the PDMS channels, controlled through the monomer to curing agent mixing ratio, did not have a noticeable influence on the system dynamic response. The models and characterization presented here allow for predicting the dynamic behavior of PDMS microchannels using simple hydraulic-circuit analysis and enable the proper design of transient microfluidic applications.College of EngineeringMultidisciplinary ProgramsMaster of Science in Mechanical Engineering (MSME
Electric Scooter Battery Management and Battery Swapping using Robotic Arm
No full textA Master of Science thesis in Mechatronics Engineering by Abeer Mazen Daoud entitled, “Electric Scooter Battery Management and Battery Swapping using Robotic Arm”, submitted in March 2024. Thesis advisor is Dr. Lotfi Romdhane and thesis co-advisor is Dr. Habib Ur Rehman. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).This thesis is motivated by the current long charging times for electric vehicles powered by lithium-ion batteries. To overcome this issue, battery swapping stations have emerged as an efficient alternative to traditional charging stations. This research focuses specifically on the growing popularity of electric scooters (e-scooters) and their need for frequent battery recharging, which limits their operational range. In response, a proposed solution that employs a robotic arm to execute battery swaps without human intervention, is proposed. This system incorporates a battery management system that constantly monitors the battery’s state of charge (SOC) and temperature, and initiates swaps under predefined conditions. A vision system is utilized to detect the battery compartment, compensating for any tilt in the parked e-scooter to ensure accurate alignment, thereby enabling the robotic arm to efficiently plan and execute the battery swap. This system requires minimal modifications to existing e-scooter designs by incorporating a specifically designed battery compartment, offers significant improvements over manual swapping methods. Furthermore, the automation extends to potential upgrades that include the integration of an Automated Guided Vehicle (AGV), transforming the system into a self-sufficient robot capable of navigating and performing battery swaps autonomously.College of EngineeringMultidisciplinary ProgramsMaster of Science in Mechatronics Engineering (MSMTR
Assessment of bent and straight GFRP reinforcement conditioned in harsh environments
No full textA Doctor of Philosophy Dissertation in Materials Science and Engineering by Ahmed Mohsen Khalil entitled, “Assessment of bent and straight GFRP reinforcement conditioned in harsh environments”, submitted in June 2024. Dissertation advisor is Dr. Rami Hawileh and dissertation co-advisor is Dr. Mousa Attom. Soft copy is available (Dissertation, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).This dissertation investigated the impact of durability on the strength of bent and straight GFRP rebars in harsh environments. The typical tensile strength observed in bent FRP rebars compared to the strength of straight rebars was on average lower by 40%, unlike conventional steel. There was a lack of studies on the durability of bent FRP bars in harsh environments like those in the UAE and Gulf region. To address this gap, two sets of durability tests were conducted, one indoors and another outdoors, with a specific focus on performance in saline environments. A comparative analysis was conducted among the results of control unconditioned samples, those exposed to the outdoor saline environment of the UAE, and those subjected to indoor accelerated durability setups in the laboratory. The aim was to identify any consistent patterns of strength deterioration in straight and bent GFRP rebars across these two testing setups (indoor and outdoor), as compared to control unconditioned specimens. The variables of the experimental program were GFRP rebar diameter, manufacturer, rebar shape, radius of curvature, durability setup, and aging duration. The results covered failure modes, load-deflection responses, strain measurements, tensile strength retention, and microstructure analysis of the GFRP rebars. Test results showed that GFRP rebars, whether straight or bent, demonstrated similar initial stiffness. However, load capacity and deflection variations were observed based on rebar size and exposure conditions. The microstructure analysis through SEM showed that the manufacturing bending process changed the cross-section of GFRP rebars from circular to approximately rectangular, which altered the load distribution and induced differential stresses along the rebar length. Additionally, environmental exposures caused notable fiber and fiber-matrix interface damage in the GFRP rebars. This study concluded that there was moderate retention of tensile strength, with an average of about 80% for the outdoor setup and 75% for the indoor accelerated setup over the exposure periods. Thus, nonmetallic GFRP reinforcement was a viable alternative to steel reinforcement in RC structures exposed to marine and harsh saline environments.College of Arts and SciencesMultidisciplinary ProgramsPhD in Materials Science and Engineering (PhD-MSE
The Impact of Social Media Influencers and Use of Nostalgia on Brand Love in Luxury Brands
No full textA Master of Business Administration (MBA) thesis by Arjun Theajonmaya entitled, “The Impact of Social Media Influencers and Use of Nostalgia on Brand Love in Luxury Brands”, submitted in December 2024. Thesis advisor is Dr. Mohammed Sajid Khan. Soft copy is available (Thesis, Approval Signatures, Completion Certificate, and AUS Archives Consent Form).Luxury brands hold a unique appeal for consumers, often evoking feelings of prestige, exclusivity, and aspiration. However, they face the challenge of capturing the attention of consumers who increasingly value experiences over possessions. Recognizing this shift in consumer behaviour, marketers are turning to nostalgia as a powerful tool to forge emotional connections and drive purchase intentions. By tapping into consumers' longing for the past and evoking feelings of warmth and familiarity, luxury brands can effectively differentiate themselves in a crowded market. Nostalgia can be used as a strategic tool to enhance brand engagement and loyalty among consumers. This study aims to investigate the influence of social media influencers on the brand love of consumers within the luxury brands sector, specifically through the lens of nostalgia. An extensive literature review is performed on topics such as brand love for luxury brands, nostalgia in luxury brands and the role of social media influencers in creating nostalgia. The proposed methodology adopted to test the model is a mixed methods approach which includes eight interviews and five focus groups comprising of five participants each.School of Business AdministrationDepartment of Management, Strategy and EntrepreneurshipMaster of Business Administration (MBA