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On the Role of Hollow Aluminium Oxide Microballoons during Machining of AZ31 Magnesium Syntactic Foam
No full textThe role played by hollow ceramic thin-walled aluminium oxide microballoons on the shear deformation characteristics of AZ31 Magnesium syntactic foam is studied through high-speed machining. The ceramic microballoons embedded in the AZ31 matrix provides the necessary stiffness for these novel foams. The effect of hollow ceramic microballoon properties, such as the volume fraction, thin wall thickness to diameter ratio, and microballoon diameter, profoundly affects the chip formation. A novel force model has been proposed to explain the causes of variation in cutting forces during chip formation. The results showed an increase in machining forces during cutting AZ31 foams dispersed with higher volume fraction and finer microballoons. At a lower (Davg/h) ratio, the mode of microballoon deformation was a combination of bubble burst and fracture through an effective load transfer mechanism with the plastic AZ31 Mg matrix. The developed force model explained the key role played by AZ31 matrix/alumina microballoon on tool surface friction and showed a better agreement with measured machining forces.American University of Sharja
Spatiotemporal Mapping and Monitoring of Mangrove Forests Changes From 1990 to 2019 in the Northern Emirates, UAE Using Random Forest, Kernel Logistic Regression and Naive Bayes Tree Models
No full textMangrove forests are acting as a green lung for the coastal cities of the United Arab Emirates, providing a habitat for wildlife, storing blue carbon in sediment and protecting shoreline. Thus, the first step toward conservation and a better understanding of the ecological setting of mangroves is mapping and monitoring mangrove extent over multiple spatial scales. This study aims to develop a novel low-cost remote sensing approach for spatiotemporal mapping and monitoring mangrove forest extent in the northern part of the United Arab Emirates. The approach was developed based on random forest (RF), Kernel logistic regression (KLR), and Naive Bayes Tree machine learning algorithms which use multitemporal Landsat images. Our results of accuracy metrics include accuracy, precision, and recall, F1 score revealed that RF outperformed the KLR and NB with an F1 score of more than 0.90. Each pair of produced mangrove maps (1990–2000, 2000–2010, 2010–2019, and 1990–2019) was used to image difference algorithm to monitor mangrove extent by applying a threshold ranges from +1 to −1. Our results are of great importance to the ecological and research community. The new maps presented in this study will be a good reference and a useful source for the coastal management organization.UAE Space Agenc
Supercapacitor Characterization Using Universal Adaptive Stabilization and Optimization
No full textThis paper presents a simplified supercapacitor model and a universal adaptive stabilization, optimization (UAS+O) based parameter identification technique. Analytic solutions for the description of supercapacitors current, voltage, subject to cyclic voltage and current sources of varying amplitudes and frequency, consistent with electric vehicle driving cycles, are developed. Supercapacitor I-V relationships show hysteresis, indicating simultaneous energy storage and dissipation mechanisms. A reduced equivalent circuit model is proposed to accurately represent hysteresis I-V characteristics. The proposed UAS+O based technique for estimating model parameters, is supported by mathematical proofs, simulation, and experimental results
An integrative study of the implications of the rise of coworking spaces in smart cities
No full textCoworking practices have proliferated around the world being embraced not only by remote workers, start-up employees and freelancers but also by larger organizations. coworking spaces in public libraries, business districts and other urban spaces, herald profound changes for the way workspaces are used in cities. The study takes an integrative approach to investigate the economic and socio-cultural implications of coworking trend for smart cities, their ecosystems and the use of urban public spaces. The study examines these issues by studying motivations and challenges of providers and users of coworking spaces. Thirty coworking spaces in urban areas across Australia were studied and thirty-four semi-structured interviews were conducted with both providers and users of the coworking spaces. The findings suggest that coworking spaces play an important role in building communities and developing social and cultural ties. From urban space and environmental perspectives, coworking spaces are likely to contribute to urban mobility and sustainability. From an urban economic perspective, coworking spaces provide a collaborative environment and often a breeding ground for entrepreneurship. Entrepreneurship is one of the most salient themes in the coworking spaces as found in this study. These findings will inform urban policy makers and help them better understand and tap into the source of civic entrepreneurship derived from coworking spaces
Polarimetric SAR Speckle Reduction by Hybrid Iterative Filtering
No full textSpeckle filtering in synthetic aperture radar polarimetry (PolSAR) is essential for the extraction of significant information. In this study, the authors introduced a hybrid iterative filtering scheme. The proposed iterative filter is initialized by a polarimetric filter ensuring a high speckle reduction level. Then, to enhance the spatial details, the iterative filter is applied for few iterations. The key parameter b k which traduced the variability of the pixels has been studied. An expression that takes into account the following important numerical considerations is proposed. 1) The variability of the pixel is measured by coefficient variation (CV) rather than the variance. 2) The statistics are computed using non-local neighborhood instead of local square one. 3) A new normalizing function (i. e. hyperbolic tangent) is implemented. 4) The dynamic of range of b k is increased by multiplying the CVs of the filtered and the originals images. Comparison with various state of the art PolSAR filters demonstrated the effectiveness of the proposed iterative method. Simulated, one-look and multilook real PolSAR data were used for validation.American University of Sharja
Big Data Energy Management, Analytics and Visualization for Residential Areas
No full textWith the rapid development of IoT based home appliances, it has become a possibility that home owners share with Utilities in the management of home appliances energy consumption. Thus, the proposed work empowers home owners to manage their home appliances energy consumption and allow them to compare their consumption with respect to their local community total consumption. This serves as a nudge in consumer's behavior to schedule their home appliances operation according to their local community consumption profile and trend. Utilizing the same common communication infrastructure, it also allows the utilities on different consumption levels (community, state, country) to monitor and visualize the energy consumption in their respective grid segments on daily, monthly, and yearly basis. A high-speed distributed computing cluster based on commodity hardware with efficient big data mathematical algorithm is employed in this work. To achieve this, two big data processing paradigms are evaluated with a set of qualitative and quantitative metrics with subsequent recommendations. One million smart meter data is simulated to access individual homes. With the utilization of distributed storage and computing cluster for handling energy big data, the utilities can perform consumer load analysis and visualization on a scale of one million consumers. This helps the utilities in providing consumers a more accurate representation of how much energy they are consuming with greater granularity and with respect to their local community. Consumer and Utility centric queries are developed to create a web-based real time energy consumption management system presented in terms of dashboard charts, graphs, and reports that can be accessed by the consumer and utility providers remotely.American University of Sharja
A New Data-Based Dust Estimation Unit for PV Panels
No full textSolar photovoltaic (PV) is playing a major role in the United Arab Emirates (UAE) smart grid infrastructure. However, one of the challenges facing PV-based energy systems is the dust accumulation on solar panels. Dust accumulation on solar panels results in a high degradation in the output power. The UAE has low intensity rainfall and wind velocity; therefore solar panels must be cleaned manually or using automated cleaning methods. Estimating dust accumulation on solar panels will increase the output power and reduce maintenance costs by initiating cleaning actions only when required. In this paper, the impact of natural dust accumulation on solar panels is investigated using field measurements and regression modeling. Experimental data were collected under various real weather conditions and controlled levels of dust. Moreover, this paper proposes a data-driven approach based on machine learning to estimate the accumulated dust level on solar panels. In this approach, a dust estimation unit based on a regression tree model has been developed to estimate the dust accumulation. This unit is trained using experimental records of solar irradiance, ambient temperature, and the output power generated from solar panels as well as the amount of dust at these conditions. The proposed unit is evaluated through different case studies with a random amount of dust applied to the solar panels to demonstrate the accurate performance of the proposed unit.American University of Sharja
Dynamic properties of language anxiety
No full textThis article begins by examining previous empirical studies to demonstrate that language anxiety, or the negative emotional reaction learners experience when using a second language (MacIntyre & Gardner, 1999), is a dynamic individual difference learner variable. I show that it forms part of an interconnected, constantly-in-flux system that changes unpredictably over multiple time scales. While at certain times this system might settle into an attractor state that accommodates contradictory conditions, perturbations that arise may lead to development and change with the curious possibility that minor disruptions generate large effects while major alterations go unnoticed. In essence, language anxiety (LA) is part of a continuous complex system in which each state evolves from a previous one. After I establish LA as a dynamic variable using the aforementioned criteria, I outline the implications and challenges for researching LA using a dynamic paradigm, which include focusing on individuals, transforming LA research questions, designing interventions and re-thinking data gathering methodologies. I conclude with implications for language teaching that emphasize: 1) raising awareness of the importance of decoding nonverbal behavior to identify moment-by-moment shifts in learner emotion; 2) remaining vigilant concerning variables that are interacting with LA that make this factor part of a cyclical process; 3) understanding that anxiety co-exists with positive emotions to varying degrees and that language tasks are not unanimously enjoyed or universally anxiety-provoking; and 4) incorporating positive psychology activities that proactively encourage buoyancy and resilience for moment-by-moment daily perturbations as well as debilitating disruptions that result in long-lasting influences
Evaluation of The Factors Affecting Microplastics and Nanoparticles in Plastic Water Supply Pipes
No full textA Master of Science thesis in Civil Engineering by Amina Rayan Hammodat entitled, “Evaluation of The Factors Affecting Microplastics and Nanoparticles in Plastic Water Supply Pipes”, submitted in November 2020. Thesis advisor is Dr. Md. Maruf Mortula. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Water distribution system (WDS) supplies good quality water to individual households. It can affect the water quality, human health, and hence the role of WDS on the water quality must be investigated. Various pipe materials have been used in WDS. However, plastic materials have been commonly used recently in pipe networks because of their low cost, durability, and other advantages. Even though plastic pipes are preferred, the supplied water can be contaminated. Disintegration of plastic particles in the form of microplastics can be a cause of concern. Although their effects on human health are still unclear, it is perceived to have a negative effect on both organisms and ecosystems. The overall aim of this thesis is to identify the presence and source of microplastics and nanoparticles in the drinking water distribution system and to investigate the effect of several parameters (pipe material, pH, chlorine and time) on the leaching of microplastics and nanoparticles. Three standard pipe loop systems were used as the experimental setup, each having a different pipe material (polyvinylchloride (PVC), polyethylene (PE), and polypropylene (PPR)). A total of twenty-seven experiments were conducted at three phases. The pH was fixed for each phase, while varying the chlorine doses, in order to study their effects on leaching microplastics and nanoparticles. Standard analytical methods were used to evaluate relevant water quality parameter. Both the visual and spectroscopic detection methods were used to identify microplastics and nanoparticles. Fourier Transform Infrared Spectroscopy (FTIR), and Scanning Electron Microscopy (SEM) with Energy Dispersive X-Ray Analysis (EDX) tests were conducted to evaluate whether the microplastics and nanoparticles are formed from the plastic pipe materials of the WDS. Results show that microplastics and nanoparticles were significantly present in the samples in different shapes and sizes. It was found that basic pH values resulted in high number of particles. As for free chlorine, no specific conclusion could be drawn. Overall, PE had the highest number of particles, followed by PPR and PVC. It was also noticed that the number of particles decreased with time. FTIR and SEM-EDX analysis was not conclusive.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
Rethinking the future low-carbon city: Carbon neutrality, green design, and sustainability tensions in the making of Masdar City
No full textAs the global trend toward urbanization continues, new models for the design and governance of sustainable cities are being developed. The Abu Dhabi government announced in 2006 its intent to spend $22 billion to build one such city, Masdar City, as a carbon-neutral, zero-waste city that would demonstrate the state-of-the-art in sustainable city design. As initially planned, Masdar City was a bold experiment: an incubator of clean-technologies that was to be powered exclusively by renewable energy while exhibiting the highest levels of energy efficiency. Partly due to the 2008 global financial crisis and partly due to lessons learned from continued assessments of the original concept, planners at Masdar both scaled back initial ambitions for the city's carbon and waste targets and significantly altered both the city's development approach and timeline for completion. This, however, may turn out to be the best outcome for Masdar City if it is truly to become a model for “eco-cities” of the future. Masdar now seeks a more commercial model that nonetheless retains a focus on sustainable urban design. This Perspective reviews the history of Masdar City from its inception to the present day and highlights the major changes that have occurred in its city planning. In consideration of the facts presented, Masdar City may yet emerge as a true eco-city. Regardless, it certainly constitutes an omen with incredibly important empirical lessons for other cities around the world seeking to become more sustainable