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Partition of Unity Finite Element Method for Solving Phase Change Problems
No full textA Master of Science thesis in Mathematics by Abdulla Hussain Kayyani entitled, “Partition of Unity Finite Element Method for Solving Phase Change Problems”, submitted in November 2023. Thesis advisor is Dr. Youssef Belhamadia. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).This thesis presents a comprehensive study of the Partition of Unity Finite Element Method (PUFEM) and its applications in solving phase change problems. First, it introduces the Finite Element Method (FEM), the classical counterpart to PUFEM, and a pivotal tool in simulating phenomena described by PDES. The limitations of FEM when handling problems with steep gradients are highlights. The thesis is dedicated to the exploration and development of PUFEM, and how it is considered as an advanced variant of FEM that incorporates enrichment functions to enable more accurate numerical solutions. The development of PUFEM is presented for the Poisson Equation, Heat Equation, and Bistable Equation showing its superior accuracy and efficiency compared to the standard FEM. Finally, the application of PUFEM for phase change problems is illustrated with detailed numerical results showing its superiority to the standard FEM offering avenues for future research.College of Arts and SciencesDepartment of Mathematics and StatisticsMaster of Science in Mathematics (MSMTH
Flexural Performance of RC Beams with Hybrid Combination of Conventional FRP and PET Laminates
No full textA Master of Science thesis in Civil Engineering by Ahmed Yousef Al Rashed entitled, “Flexural Performance of RC Beams with Hybrid Combination of Conventional FRP and PET Laminates”, submitted in March 2023. Thesis advisor is Dr. Rami A. Hawileh and thesis co-advisor is Dr. Jamal A. Abdallah. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Externally bonded fiber-reinforced polymer (FRP) composites are widely used to strengthen reinforced concrete (RC) beams. However, due to composites' brittleness, strengthened beams usually fail by premature brittle debonding of the FRP laminates. Delaying this failure mode enhances the beams’ flexural capacity and ductility. This work aims to study the effect of balancing traditional high-strength FRPs with polyethylene terephthalate (PET-FRP) laminates. Unlike conventional FRPs, PET-FRP has a bilinear stress-strain relationship and ruptures at large strains exceeding 7%. However, it has lower elastic modulus and tensile strength than conventional FRPs. To compensate for this drawback, the effect of hybridizing carbon-FRP (CFRP) and glass-FRP (GFRP) with PET-FRP laminates is examined. In addition, to enhance the effectiveness of the strengthening systems and delay FRP debonding, the effect of anchoring using end U-wraps is explored. Twenty-seven RC beams, strengthened with different combinations of layers and stacking sequences of hybrid CFRP, GFRP, and PET-FRP laminates and with and without end U-wrap anchors, were tested to failure. The results of the strengthened anchored beams were compared to the un-anchored strengthened beams and un-strengthened control beams. Results showed that hybrid combinations of PET, CFRP, and GFRP laminates provided enhanced flexural performance over CFRP and GFRP-strengthened specimens. The enhancement depended on the number of strengthening sheets, type of FRPs, stacking sequence, and presence of anchors. The enhancement in the load-carrying capacity and ductility ranged from 23% to 70% and -17% to 92%, respectively. Results proved that side anchors effectively prevented premature failure due to debonding or delamination. The highest load-carrying capacity and ductility enhancement were exhibited by the PGP anchored specimen. The load-carrying capacity of the strengthened beams was predicted using the ACI 440.2R-17 and CEB-FIB design guidelines. It can be concluded that combining PET with CFRP and GFRP laminates could provide a robust strengthening system that enhances both the strength and ductility of RC beams in flexure.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
Recruitment and Selection Practices that Facilitate Workforce Diversity in Public Sector
No full textThe objectives of this chapter paper are to review and summarise the recruitment and selection practices that facilitate workforce diversity in the public sector, and to offer promising directions for future research. First, the main recruitment practices that facilitate workforce diversity in PS include 1) setting quotas, targets, or reserving specific positions, 2) developing and communicating an attractive employee value proposition, 3) eliminating discriminatory selection criteria, and 4) using diversified, proactive, targeted recruitment methods. Second, the main selection practices that facilitate the hiring of a diverse workforce include implementing 1) flexible selection processes, 2) non-discriminatory selection testing and interviewing processes, and 3) inclusive and trained selection committees. To conclude, we propose interesting avenues for future research. This chapter will assist scholars and practitioners to develop a more comprehensive understanding of the specific issues related to diversity management in in the public sector
Flexural Performance of Concrete Beams Strengthened Using CFRP Sheets with Large Spike Anchors
No full textA Master of Science thesis in Civil Engineering by Maha A. Assad entitled, “Flexural Performance of Concrete Beams Strengthened Using CFRP Sheets with Large Spike Anchors”, submitted in March 2023. Thesis advisor is Dr. Rami Haweeleh and thesis co-advisor is Dr. Jamal Abdalla. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Fiber-reinforced polymers (FRP) have a proven strength enhancement capability when attached to reinforced concrete (RC) beams. However, the inherent brittleness of FRP composites largely sacrifices the full load-carrying capacity of externally bonded FRP strengthening systems. The use of carbon fiber-reinforced polymers (CFRP) splay anchors has demonstrated positive outcomes in terms of enhancing the capacity of strengthened members and mitigating debonding. Limited research studies have been carried out to examine the effect of CFRP splay anchor parameters on the flexural behavior of RC beams anchored with small diameter anchors. The aim of this study is to examine the effect of large anchors, specifically, anchors with a diameter of more than 14 mm. Accordingly, a total of seventeen beams were cast and tested under four-point bending test. Fifteen beams were strengthened using CFRP sheets and anchored with different configurations of CFRP spike anchors. The investigated variables in the experimental program are anchor’s dowel diameter, embedment depth, fan length, insertion angle, and number of anchors. Test results of the anchored specimens in terms of load-deflection responses, failure modes, strain in the concrete, steel reinforcement, and CFRP laminates were compared to that of the control unstrengthened and unanchored strengthened specimens. The test results indicate that CFRP anchors enhanced the strength of the CFRP laminates by 12-53% over the unanchored specimens. It was observed that larger diameter anchors provided a considerably improved strength enhancement compared to smaller diameter anchors, on average by 28%. It was also concluded that bonding CFRP laminates by well-designed CFRP anchors highly utilized the strain attained in CFRP laminates. In addition, the flexural strength of the anchored beams is predicted using the ACI440.2R-17, CSA-S806.12(R2017), and fib-14 design guidelines. Based on comparison with the experimental results, the ACI440.2R-17 and fib-14 provisions provided reasonable predictions according to the debonding/delamination equation and assuming no fully bonded action is developed due to anchorage.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
A Low-Cost Process for Fabricating Reinforced 3D Printing Thermoplastic Filaments
No full textLow-cost desktop-sized fused deposition modeling (FDM) printers have been widely embraced by small to large-scale institutions and individuals. To further enhance their utility and increase the range of materials that they can process, this work proposes a low-cost solution that adapts to low-cost desktop-sized extruders and enables them to fabricate filaments comprising a wide range of nonorganic reinforcing particles. This solution will fill a gap in the field, as low-cost fabrication techniques for reinforced filaments have been lacking. In the proposed solution, particles are heated and deposited on thermoplastic pellets to form a coating. Coated pellets are subsequently extruded using a low-cost desktop single-screw extruder. The effectiveness of the process is demonstrated by fabricating polylactic acid (PLA) filaments reinforced with two types of reinforcements, namely, dune sand and silicon carbide. Filaments’ stiffness and strength were measured, and their microstructure along their lateral and longitudinal directions were investigated. Improvements in tensile strength (up to 8%) and stiffness (up to 4.5%) were observed, but at low reinforcement levels (less than 2 wt%). Results showed that the proposed process could be used to fabricate filaments with multiple types of particles. The produced filaments were successfully used to fabricate 3D parts using a commercial desktop FDM printer.American University of Sharja
Neuroprotective Role of Hypothermia in Acute Spinal Cord Injury
No full textEven nowadays, the question of whether hypothermia can genuinely be considered therapeutic care for patients with traumatic spinal cord injury (SCI) remains unanswered. Although the mechanisms of hypothermia action are yet to be fully explored, early hypothermia for patients suffering from acute SCI has already been implemented in clinical settings. This article discusses measures for inducing various forms of hypothermia and summarizes several hypotheses describing the likelihood of hypothermia mechanisms of action. We present our objective neuro-electrophysiological results and demonstrate that early hypothermia manifests neuroprotective effects mainly during the first- and second-month post-SCI, depending on the severity of the injury, time of intervening, duration, degree, and modality of inducing hypothermia. Nevertheless, eventually, its beneficial effects gradually but consistently diminish. In addition, we report potential complications and side effects for the administration of general hypothermia with a unique referment to the local hypothermia. We also provide evidence that instead of considering early hypothermia post-SCI a therapeutic approach, it is more a neuroprotective strategy in acute and sub-acute phases of SCI that mostly delay, but not entirely avoid, the natural history of the pathophysiological events. Indeed, the most crucial rationale for inducing early hypothermia is to halt these devastating inflammatory and apoptotic events as early and as much as possible. This, in turn, creates a larger time-window of opportunity for physicians to formulate and administer a well-designed personalized treatment for patients suffering from acute traumatic SCI.Hong Kong Baptist Universit
Evaluation of the Factors Impacting the Water Pipe Leak Detection Ability of GPR, Infrared Cameras, and Spectrometers under Controlled Conditions
No full textLeakages from water distribution infrastructures are responsible for a considerable amount of water losses. Consequently, innovative, non-destructive techniques (NDT) of leakage detection for early recognition is vital. In this study, the leak detection abilities of Ground Penetration Radar (GPR), spectrometers, and infrared (IR) cameras were investigated, and the factors affecting the leak detection response were assessed. Three experimental setups were constructed to simulate underground pipes in dune sand. Three different pipe materials (PVC, PPR, and PE) were investigated under three levels of moisture content (MC; 2%, 5%, and 10%) and three types of leaks (hole, crack, and faulty joint). The IR camera was the most effective among the different NDTs used in this study. The IR camera detected all types of leaks at 2% and 5% MC but was inconclusive at 10% MC. Similarly, the GPR detected the leaks at 2% and 5% MC successfully but was inconclusive at 10% MC. Lastly, the spectrometer was the least reliable NDT to detect leaks. Results suggest that IR cameras and spectrometers that operate in the mid-IR range (5–25 µm) can detect leaks.American University of SharjahSharjah Research AcademyOpen access program from American University of SharjahProfessional development grant from American University of Sharja
Examining the Deviation in Energy Saving Estimations Due to the Use of the Degree Days Method
No full textEnergy performance contracts are commonly used to retrofit buildings and reduce their energy consumption. The financial agreement in the contracts typically depends on calculating the amount of energy saved every year. This is difficult to calculate as many aspects that impact a building’s energy consumption continuously change, including the weather. The Degree Days method is commonly used to help estimate the energy saving while the weather is changing. The Degree Days can be calculated with a variety of base temperatures resulting in different values. This paper is a first step in examining the significance of the deviation in energy saving calculations when using this method. It also investigates if there is a more appropriate base temperature to use for that purpose. Energy simulation with actual annual weather data is used to make the investigation. Two different building types and three different energy conservation measures are used. The results of this preliminary investigation show that the deviation can be significant in some cases. They also show the possibility that a particular base temperature for calculating the degree days can give more accurate savings estimations. These can be very important results for users of energy performance contracts
Flexural Performance of FRP-Reinforced Concrete Beams Using Ultra High Strength Concrete
No full textA Master of Science thesis in Civil Engineering by Zin Subhi Mahaini entitled, “Flexural Performance of FRP-Reinforced Concrete Beams Using Ultra High Strength Concrete”, submitted in April 2022. Thesis advisor is Dr. Farid Abed. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).This research investigated the flexural performance of beams reinforced with fiber reinforced polymer (FRP) bars and cast using Ultra High Strength Concrete (UHSC) with a nominal compressive strength of 140 MPa. A total of fifteen beams were prepared and tested in a four-point loading setup. Ten specimens were reinforced with Glass FRP (GFRP) bars and two specimens were reinforced with Basalt FRP (BFRP) bars. The other three beams were reinforced with conventional steel as reference specimens. The FRP reinforced beams were designed to have either tension-controlled or compression-controlled modes of failure to examine the different responses between them. All beams had 185 mm width, 250 mm depth, and 2200 mm total span length. The influence of different variables including reinforcement ratio, number of longitudinal bars, and reinforcement type was investigated in terms of strain values, midspan deflections, flexural capacities, and cracking responses. The test results showed that the over-reinforced FRP-UHSC beams displayed acceptable deflections at service loads and had adequate ductility prior to failure. Results also showed that the use of GFRP bars in UHSC beams increased the flexural capacity up to 70.15% compared to steel reinforced beams. The BFRP bars were also found to be valuable alternatives to GFRP bars in flexural members. In addition, the analytical predictions compared well with the experimental values of cracking moments and flexural capacities. However, the ACI 440 and CAN/CSA S806 approaches for calculating midspan deflections underestimated the deflections, especially for over-reinforced FRP-UHSC beams.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE