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A Simple Model for the Fields of a Chirped Laser Pulse With Application to Electron Laser Acceleration
No full textA simple model is introduced for the fields of a chirped laser pulse. As an application, dynamics of laser-acceleration of a single electron by the fields of a pulse, with a sin4 envelope, is investigated. Multi-GeV energy gains from interaction with pulses of peak intensity I0 ∼ 1020 W/cm2, are reported
Design and Characterization of Flexible and Implantable Electrodes
No full textA Master of Science thesis in Biomedical Engineering by Aseel Dirar Alatoom entitled, “Design and Characterization of Flexible and Implantable Electrodes”, submitted in April 2019. Thesis advisor is Dr. Amani Al-Othman and thesis co-advisors are Dr. Hasan Awad Moh'd Al-Nashash and Dr. Mohammad Hussein Al-Sayah. Soft and hard copy available.Implantable bioelectrodes have the potential to advance neural sensing and muscle stimulation, especially in cases of peripheral nerve injuries. In such cases, the application of electrical stimulation to the muscles prevents muscular atrophy and helps to bridge the gap between the injured nerve and the corresponding muscle. Conventional materials for these implantable electrodes are usually metals, but they suffer from several limitations ranging from mechanical mismatch to immunological responses. Another problem is damage to tissues due to mechanical forces exerted on soft tissues by the stiff mechanical electrodes. Therefore, there is a need for the development of flexible, durable implantable electrodes with low interfacial impedance characteristics. This thesis discusses the fabrication and characterization of novel, low-cost, flexible bioelectrodes based on silicone polymer (polysiloxane) and other electrode materials, including titanium dioxide and stainless steel powder as well as their combinations. For this purpose, this work synthesized and characterized three types of implantable electrodes based on their electrochemical and mechanical properties; where titanium dioxide, stainless steel, and a mixture of the two were used as the main conducting components for fabrication. The titanium dioxide-based samples exhibited a bulk impedance of 353±13.5 Ω with an impedance of 198±183 kΩ at frequency of 1 kHz; in addition, they had a modulus of elasticity of 4.52±1.15 MPa. The stainless steel-based electrodes had a bulk impedance of 1.69±1.16 kΩ and an impedance of 1.21±1.13 MΩ at frequency of 1 kHz, and they had a modulus of elasticity of 0.722±0.393 MPa. The third type, which was a mixture of both titanium dioxide and stainless steel-based samples, had a bulk impedance of 1.71±0.849 kΩ and an impedance of 191 ± 160 kΩ at frequency of 1 kHz; along with a modulus of elasticity of 0.453±0.32 MPa. The results for the silicone with metal powders showed promising electrochemical and mechanical characteristics with flexible and ductile properties, with the titanium dioxide-based material performing the best. Compared with the values reported in the literature, the results show superior performance. Thus, supporting the composite material’s potential for being used in implantable electrode applications.College of EngineeringMultidisciplinary ProgramsMaster of Science in Biomedical Engineering (MSBME
The flexural behavior of bolting and bonding Aluminum Alloy plates to RC beams
No full textThe aim of this experimental investigation is to study the effect of using externally bonded and bolted Aluminum Alloy (AA) plates on the strength, stiffness, ductility and failure modes of Reinforced Concrete (RC) beams. The test matrix of this study consisted of three RC beams including one unstrengthened control beam and the other two beams were externally strengthened with AA plates using two types of strengthening techniques – bonding only and bolting as anchorage in addition to bonding. The specimens were tested under monotonic loading until failure. The results indicated that the beam with bonded AA plates showed a 32% increase in load capacity and 45% increase in deflection compared to the control beam, whereas the beam with bolted and bonded AA plates showed a 24% increase in load capacity and 84% increase in deflection compared to the control beam. It was concluded that the combination of bolting and bonding, as an alternative anchorage technique, greatly enhanced the ductility in the strengthened specimen and reduced the debonded length of the AA plate while scarified a relatively small reduction in the beam’s capacity as a trading off
Modeling and simulation of hypothermia effects on cardiac electrical dynamics
No full textPrevious experimental evidence has shown the effect of temperature on the action potential duration (APD). It has also been demonstrated that regional cooling of the heart can prolong the APD and promote the termination of ventricular tachycardia. The aim of this study is to demonstrate the effect of hypothermia in suppressing cardiac arrhythmias using numerical modeling. For this purpose, we developed a mathematical model that couples Pennes’ bioheat equation and the bidomain model to simulate the effect of heat on the cardiac action potential. The simplification of the proposed heat–bidomain model to the heat–monodomain model is provided. A suitable numerical scheme for this coupling, based on a time adaptive mesh finite element method, is also presented. First, we performed two-dimensional numerical simulations to study the effect of heat on a regular electrophysiological wave, with the comparison of the calculated and experimental values of Q10. Then, we demonstrated the effect of global hypothermia in suppressing single and multiple spiral waves
Estimating Dust Accumulation on Photovoltaic Modules in the UAE
No full textA Master of Science thesis in Electrical Engineering by Amal AbdulAziz AlArif entitled, “Estimating Dust Accumulation on Photovoltaic Modules in the UAE”, submitted in May 2019. Thesis advisor is Dr. Mostafa Shaaban. Soft and hard copy available.Among the challenges facing solar photovoltaic (PV) systems in the United Arab Emirates (UAE), dust is considered the most severe problem that faces the growth of solar power plants. Dust accumulation on solar PV panels results in a degradation in the output power. The UAE has a low intensity of rainfalls and wind velocity; thus, solar PV panels must be cleaned manually or using automated cleaning methods which are costly. Estimating dust accumulation on solar PV panels will increase the output power of solar PV power plants and reduce maintenance costs by initiating cleaning actions only when required. In this thesis, the effect of natural dust accumulation on solar PV panels is investigated using field measurements and regression modeling. Experimental data were collected under various weather conditions and controlled levels of dust. Solar PV output power, ambient temperature, solar irradiance, and dust were monitored in a period of two months to collect sufficient data for constructing a dust estimation model. Regression models were trained and tested to develop an accurate model for estimating the dust accumulated on solar PV panels in the UAE. The developed fine tree regression model provided accurate dust accumulation prediction with Root Mean Square Error (RMSE) of\ 0.0255 g/m2. The model was tested on different case studies with a random amount of dust applied the solar PV panels to confirm the accuracy of the developed model.College of EngineeringDepartment of Electrical EngineeringMaster of Science in Electrical Engineering (MSEE
3D Printing Technology Utilizing Available Construction Materials in the UAE
No full textA Master of Science thesis in Civil Engineering by Sara Khaled Ahmed entitled, “3D Printing Technology Utilizing Available Construction Materials in the UAE”, submitted in November 2019. Thesis advisor is Dr. Sherif Yehia. Soft copy is available (Thesis, Approval Signatures, Completion Certificate, and AUS Archives Consent Form).Over the past decade, rapid developments in 3D printing technology was observed within the construction industry. 3D printing is an innovative construction technique which may be referred to as automated construction, digital or additive manufacturing. This technology has the ability to build complex structures with no formworks, reduces construction costs and material usage, which will allow for the adoption of a sustainable built environment. However, there are still many challenges that limit the capabilities of 3D printing. To develop concrete which is pumpable, extrudable, and buildable, the workability of the fresh printing concrete is the key factor that has to be evaluated and monitored over time. This study aims to develop a 3D printing concrete using locally available materials and to asses it in terms of its fresh properties. The experimental program involved two phases. In phase 1 evaluation two groups of mixes were developed mainly to examine the effect of supplementary cementitious materials (Ground-granulated blast-furnace slag and Silica fume) on the extrudability and compressive strength. The optimal mix of phase one was found to be the mix containing both crushed and dune sand, and GGBS and SF combined. In phase 2 evaluation, the optimal mix was selected from phase 1, and was developed with three different aggregate to binder (a/b) ratios of 1.2, 1.5, and 1.8. The evaluation criteria included the extrudability, setting-time, open-time, workability, and buildability of the mixes. The workability was assessed in terms of the penetration, slump, and flow. The results of phase two suggest that the extrudability was best monitored with the flow test as compared to the slump and penetration tests. The optimal slump and flow percentage ranges that maintain acceptable extrudability were 85-0 mm and 90-45%, whereas, the buildability was performed at a slump and flow of 45-50 mm and 66%. The increase in a/b ratio led to mixes with higher buildability. Finally, the compressive strength of printed specimens of phase 2 mixes was also evaluated and the results demonstrated that the strength of the specimens decreased with the increase in a/b ratio.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
Experimental Investigation of FRP-Reinforced Concrete Columns Under Concentric and Eccentric Loading
No full textA Master of Science thesis in Civil Engineering by Nouran Zinelabdin Ahmed Elmesalami entitled, “Experimental Investigation of FRP-Reinforced Concrete Columns under Concentric and Eccentric Loading”, submitted in June 2019. Thesis advisor is Dr. Farid Abed and thesis co-advisor is Dr. Ahmed Elrefai. Soft and hard copy available.The problem of corrosion of steel in reinforced concrete (RC) structures has urged the need for alternative reinforcement materials. One possible alternative is fiber-reinforced polymer (FRP) bars, which are non-corrosive, non-magnetic, and have higher tensile strengths and higher strength-to-weight ratios than steel bars. Nevertheless, owing to the low compressive strength of FRP bars, the currently available FRP RC design codes, such as ACI440.1R-15 and CSA S806-12, neglect the contribution of FRP bars to the columns’ ultimate capacities. In this study, the behavior of concrete columns reinforced with a relatively new type of FRP bars, basalt fiber-reinforced polymer (BFRP) bars, as well as glass fiber-reinforced polymer (GFRP) bars, is investigated. The study starts with a critical literature review on FRP-reinforced concrete columns, followed by analysis of experimental tests conducted on a total of 22 reinforced concrete square columns. The overall response of FRP RC columns is investigated considering several key parameters such as longitudinal reinforcement type (steel, GFRP and BFRP), BFRP longitudinal reinforcement ratio, transverse reinforcement type (steel and BFRP ties), BFRP transverse reinforcement spacing, and loading eccentricity (concentric and eccentric). The results showed that FRP RC columns demonstrated overall compression behavior similar to steel RC columns. Even though FRP RC columns had lower ultimate capacities than steel RC columns, the difference in the ultimate capacities decreased as load eccentricity increased. Moreover, FRP RC columns showed higher ductility than steel RC columns, at all load eccentricities. However, the contribution of FRP bars to the ultimate capacities of the columns was around 11% as compared to 31% for steel bars. Despite this, neglecting the strength contributions of FRP bars, as recommended by current FRP RC design codes, results in conservative predictions of the columns’ ultimate capacities. BFRP ties are found to be efficient in confining the concrete core and in increasing the columns’ deformation capacities. Reducing BFRP ties spacing would have more pronounced effect on confinement efficiency and ductility than on strength capacity of FRP RC columns.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
An Innovative Approach for a Better Tsunami Warning System
No full textA poster submitted in ENG 207 taught by Dr. Philip McCarthy for the Spring 2019 semester.Tsunamis are among the most destructive natural disasters, however most tsunamis can be detected before hitting the shore. Therefore, we dedicated our project to develop an innovative system with a better tsunami detection, improved communication methods and enhanced evacuation protocols
Intelligent Speed Adaptation
No full textA poster submitted in ENG 207 taught by Dr. Philip McCarthy for the Spring 2019 semester.Conforming to laws and regulations is vital to road safety. As the European Commission stated in 2012, "The main causes of fatal accidents are speeding, driving under the influence of alcohol, and non-use of a seat belt." Now, in the age of Artificial Intelligence (AI), integrating AI into speed control systems would make vehicles capable of reacting to speeding without the intervention of the driver
The Use of Transferrin and Ultrasound in Cancer Treatment
No full textA Master of Science thesis in Biomedical Engineering by Nour Majdi AlSawaftah entitled, “The Use of Transferrin and Ultrasound in Cancer Treatment”, submitted in May 2019. Thesis advisor is Dr. Ghaleb Husseini. Soft and hard copy available.Site-specific drug delivery represents an attractive approach in cancer treatment to reduce the undesirable side-effects of anticancer therapeutics and increase the accumulation of drugs at tumor sites. Surface modification of nanoparticles such as liposomes with targeting moieties specific to the receptors on the surface of tumor cells further improves the selectivity of liposomes, while external triggers such as ultrasound can be used to enhance the release of liposomal contents. In this study, the anticancer activity of PEGylated calcein-loaded liposomes targeted with transferrin (Tf) was evaluated. The sizes of liposomes were measured using dynamic light scattering; control liposomes were found to have an average diameter of 82.70±2.88 nm while transferrin liposomes had an average diameter of 87.54±4.81 nm. The presence of transferrin was established using the bicinchoninic acid (BCA) assay, and the total lipid content was quantified using the Stewart assay. Next, low-frequency ultrasound (LFUS) of 20 kHz at three power densities (7.46, 9.85, and 17.31 mW/cm2) and high-frequency ultrasound (HFUS) at two frequencies (1.07MHz and 3MHz) were used to release the contents of 3 batches of control and transferrin liposomes. For LFUS, the release profiles showed an increase in calcein release with increased power density and that transferrin-conjugated liposomes have a significantly higher release when compared to non-targeted liposomes at all three power densities. In addition, nine drug release kinetics’ models were utilized to model the LFUS release profiles. For both types of liposomes, the best fitting models were Korsmeyer-Peppas, Hixson-Crowell, Weibull and Hopfenberg. With regard to HFUS release; both types of liposomes showed a clear increase in release after each insonation; however, the release at 1.07 MHz was higher than that of 3 MHz even though the power density was higher at 3 MHz. Moreover, the release profile for transferrin liposomes showed a more linear increase with time, and the fraction release values tended to be higher than those obtained for control liposomes for both frequencies. Finally, the results of the in-vitro cell work indicated that Tf-modified liposomes coupled with US were able to enhance the intracellular uptake and cytotoxicity of the entrapped calcein by HeLa cells by around 80.09±30.08% compared to control liposomes.College of EngineeringMultidisciplinary ProgramsMaster of Science in Biomedical Engineering (MSBME