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Poly(lactic acid) (PLA) and polyhydroxyalkanoates (PHAs), green alternatives to petroleum-based plastics: a review
No full textIn spite of the fact that petroleum-based plastics are convenient in terms of fulfilling the performance requirements of many applications, they contribute significantly to a number of ecological and environmental problems. Recently, the public awareness of the negative effects of petroleum-based plastics on the environment has increased. The present utilization of natural resources cannot be sustained forever. Furthermore, oil is often subjected to price fluctuations and will eventually be depleted. The increase in the level of carbon dioxide due to the combustion of fossil fuel is causing global warming. Concerns about preservation of natural resources and climate change are considered worldwide motivations for academic and industrial researchers to reduce the consumption and dependence on fossil fuel. Therefore, bio-based polymers are moving towards becoming the favorable option to be utilized in polymer manufacturing, food packaging, and medical applications. This paper represents an overview of the feasibility of both Poly Lactic Acid (PLA) and polyhydroxyalkanoates (PHAs) as alternative materials that can replace petroleum-based polymers in a wide range of industrial applications. Physical, thermal, rheological, and mechanical properties of both polymers as well as their permeability and migration properties have been reviewed. Moreover, PLA's recyclability, sustainability, and environmental assessment have been also discussed. Finally, applications in which both polymers can replace petroleum-based plastics have been explored and provided
A multi-objective planning approach for optimal DG allocation for droop based microgrids
No full textThis paper proposes a multi-objective planning approach to determine the optimal DG locations for droop-based microgrids. A secondary control operating region is mathematically formulated and incor-porated in the multi-objective optimization problem to constrain the optimal droop characteristic within the acceptable frequency and voltage thresholds. The proposed planning problem is formulated as a Mixed Integer Non-Linear Programming (MINLP) problem and is tested on a modified version of the IEEE 38 bus system operated as an islanded microgrid. The proposed approach is applied to the three most common microgrid control strategies: P-f/Q-V droop, the P-V/Q-f droop and master/slave. The proposed formulation is compared to existing planning algorithms for droop-based microgrids. The re-sults show that including the secondary control region in the optimization problem achieves lower volt-age deviations and no frequency deviations at all demand levels. The optimal DG allocation solution may vary from the cases where the droop gains or references are fixed.American University of Sharja
Rethinking the Bottom Bun: Assessing Topic Closers
No full textA Master of Arts thesis in Teaching English to Speakers of Other Languages (TESOL) by Anuja Mariyam Thomas entitled, “Rethinking the Bottom Bun: Assessing Topic Closers”, submitted in May 2021. Thesis advisor is Dr. Philip McCarthy. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).This study focusses on the learnability of a model for topic closers. Topic closers are the various approaches through which a paragraph can be ended. The model comprises a total of 10 topic closers, each of which is termed a Label. The current study explores students’ ability to recognize the various Labels of the model. To assess the learnability of the model, I used a pretest-intervention-posttest experimental design. For the pretest, I presented participants with 50 topic closer sentences and asked them to rate each sentence on a scale of 1-6 for effectiveness. Following the pretest, I presented participants with an explanation document that details all relevant information. The posttest assessment repeated the method used in the pretest with a different set of 50 sentences. The results were analyzed using two sets of criteria: Average scores and variance scores. Average is the mean of the scores for each Label and is used to assess whether overall scores for each Label rise or fall. Variance is the distance from the mean for each Label and is used to calculate how consistently students recognize each label. The results were conducted using R statistical software to assess both between and within ANOVA analyses. Averages of the Labels deemed more effective saw a rise in posttest values, while averages of the Labels deemed less effective saw a fall. The results for average scoring suggest that students can distinguish more effective examples of topic closers from less effective examples of the same. Additionally, there was a significant fall in variance scores across all data. The results for variance scoring suggest that students gained confidence in their evaluations. As such, we can conclude that the intervention resulted in a significant level of learning. Qualitative analysis was also conducted with the analyses supporting the quantitative results. The results of this study have implications for both classroom learning as well as for intelligent tutoring systems.College of Arts and SciencesDepartment of EnglishMaster of Arts in Teaching English to Speakers of Other Languages (MA TESOL
Implementation of a Smart Storage System for Fruit Quality Preservation
No full textA Master of Science thesis in Engineering Systems Management by Raed Okba AlZuabi entitled, “Implementation of a Smart Storage System for Fruit Quality Preservation”, submitted in February 2021. Thesis advisor is Dr. Noha Mohamed Hassan Hussein and thesis co-advisor is Dr. Zied Bahroun. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Food packaging has evolved throughout the decades from being a simple container to hold food, to being an active agent in the role of preserving the product’s shelf life. However, according to the Food and Agriculture Organization, almost 1.3 billion tons of food is wasted annually due to either overbuying, overproduction, or even spoilage if left untouched. In addition, due to the increasing population growth and the continuing reduction of the world’s arable lands, the need for advanced packaging systems has never been more crucial. Therefore, this research implements a cost-effective and sustainable smart fruit storage system in which active and intelligent packaging techniques are combined in order to enhance the quality of the fruits. To this end, a literature review on the negative issues affecting the quality of fruits as well as the different types of smart packaging techniques is conducted. Based on the findings from the literature, a smart fruit packaging system was designed and manufactured using thin aluminum sheets due to its conductivity and cost-effectiveness. An experimental analysis is then executed using bananas and avocadoes inside and outside the packaging system while regulating the air composition and relative humidity within the compartment using Argon and Carbon gas, as well as Potassium Chloride powder. The data collected was used to study and analyze the differences in air quality measurements using Minitab through response surface regression analysis and factorial plots, as well as the color quality of the fruits (RGB Values) through correlation. The results of both analyses indicate a reduction in fruit respiration and an increase in shelf life between the fruits inside and outside the compartment. The fruits placed inside the packaging system had their shelf life extended by at least 2 times the normal duration respectively. Finally, an economic analysis is conducted to estimate the public price of the packaging system if sold to families of 4 – 5 members, while also estimating the benefits in terms of savings over the course of 4 years. The economic analysis generated a positive Internal Rate of Return (IRR) equal to roughly 22%.College of EngineeringMultidisciplinary ProgramsMaster of Science in Engineering Systems Management (MSESM
Adapting to transnational education: students’ experiences at an American university in the UAE
No full textPurpose – Despite the increasing number of transnational universities around the world, little attention has been paid to students who attend foreign universities in their own countries and their adjustment to the new learning environment. This study aims to examine some of the adaptations freshmen students have to undergo while studying at an American university in the United Arab Emirates (UAE). Design/methodology/approach – This study is conducted at an American university in the UAE and involved 152 freshmen students, investigating their challenges to adapting to the university academically and socially. The target respondents were first-year students, typically 18–19 years old men and women of various majors and nationalities who completed high school in the country. Questionnaires were emailed to students; a total of 184 surveys were completed (with prior permission), but only 152 of those fitted the criteria and were used in the study. Findings – Findings indicate that although these students study at home, by attending a foreign university many of them rely heavily on the support of peers, especially co-nationals. They require similar academic and emotional support from teachers as many first-year students at university do. Research limitations/implications – The findings have limitations as data were collected at a single point in time through surveys. Being a single researcher, the study did not opt for breadth to answer the research questions but aimed to find out freshmen students’ challenges in adapting to the university. Despite the limitations of the study, several issues were raised that can be investigated in future studies. Originality/value – The study provided insights into the challenges first-year students face at a transnational university in the UAE. It identifies the support that could be provided by the university to facilitate students’ successful adjustment process to the educational and socio-cultural environment of the university. Although this was small-scale research and cannot be generalized to a larger population, the findings could be transferable to other, similar settings in transnational universities in the region. Findings might be compared and contrasted to other, related cases, as the structural aspects could be noticed in similar cases or situations
Flexural Behavior of Concrete Beams Reinforced with FRP Bars Under Long Exposure to UAE Environment
No full textA Master of Science thesis in Civil Engineering by Hakem Mohammad Alkhraisha entitled, “Flexural Behavior of Concrete Beams Reinforced with FRP Bars Under Long Exposure to UAE Environment”, submitted in March 2021. Thesis advisor is Dr. Farid Abed. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Due to the large research pool of Fiber-reinforced Polymers (FRP) reinforcements, their utilization as main reinforcement in concrete structures has gained the trust of the engineering community. In fact, design codes such as the ACI 440.1R and the CSA S806 have been written due to the extensive research conducted in the realm of FRP reinforcement. The previously stated guidelines, however, do not include provisions for Basalt FRP reinforcements. In addition, research about the impact of harsh environments on the behavior of FRP reinforcement is scarce. In this study the flexural behavior and serviceability performance of Glass and Basalt FRP reinforcement exposed to a combination of ultraviolet rays, humidity, and rain for a period of 28 months were investigated. Specifically, the effects of the UAE climate on the flexural capacity of FRP Reinforced Concrete (RC) beams were examined. Additionally, bond-dependent coefficient (kb) values were evaluated. The study also aims to evaluate the effects of reinforcement ratio, reinforcement surface texture, beam detailing, and reinforcement type on the flexural behavior and serviceability of FRP RC beams. In total, six sand coated GFRP RC beams, six ribbed GFRP RC beams, and nine sand coated BFRP beams were tested. In addition, one Carbon FRP RC beam and one steel RC beam were used as reference beams. It was concluded that exposure had a larger impact on the serviceability performance than it had on the flexural behavior of the beams. The kb factor for all beams in this study was averaged to be 0.82 which is less than the 1.4 kb factor recommended by the ACI 440.1R code. The average kb factor for beams reinforced with exposed ribbed GFRP bars was 7% higher than that of beams reinforced with the unexposed ribbed GFRP bars. However, the kb factor was not affected by exposure variation in the BFRP RC beams. The study concluded that even with harsh exposure to the UAE climate, FRP bars are still resilient enough to be used in construction. Although FRP bars subjected to exposure showed inferior performance to their unexposed counterparts, they still showed superior performance when compared with steel reinforcement.College of EngineeringDepartment of Civil EngineeringMaster of Science in Civil Engineering (MSCE
Tracking the Commitment to Sustainable Development Decisions
No full textA Doctor of Philosophy Dissertation in Engineering Systems Management by Mustafa Sahban Al Tekreetii entitled, “Tracking the Commitment to Sustainable Development Decisions”, submitted in April 2021. Dissertation advisor is Dr. Salwa M. Beheiry and dissertation co-advisor is Dr. Vian Ahmed. Soft copy is available (Thesis, Completion Certificate, and AUS Archives Consent Form).College of EngineeringMultidisciplinary ProgramsPhD in Engineering - Engineering Systems Management (PhD-ESM
Neural network based predistortion of radio frequency power amplifiers
No full textA Master of Science thesis in Electrical Engineering by Anfal Alsayed Ali entitled, “Neural network based predistortion of radio frequency power amplifiers”, submitted in April 2021. Thesis advisors are Dr. Oualid Hammi and Dr. Usman Tariq. Soft copy is available (Thesis, Completion Certificate, Approval Signatures, and AUS Archives Consent Form).Over the last few decades, researchers have been able to successfully use neural networks for behavioral modeling and predistortion of power amplifiers. When used as predistorters, neural networks offer favorable results due to their ability to perform complicated tasks and model nonlinear systems. The main downside of neural network predisorters is their large number of coefficients which increases their complexity. This research proposes four hybrid neural network predistorter models that combine a real-valued focused time-delay neural network (RVFTDNN) with a memory polynomial, or a generalized memory polynomial. The aim of the proposed models is to reduce the complexity of the predistorter while maintaining its performance. The proposed models have been validated for linearizing three power amplifiers: a Doherty PA driven by a 1-carrier LTE signal with a 5MHz bandwidth, a Doherty PA driven by a 4-carrier (1001) LTE signal with a 20MHz bandwidth, and the PA provided by RF WebLab, at Chalmers University, Sweden. This latter device under test was driven by a 1-carrier LTE signal with a 20MHz bandwidth. Each power amplifier was linearized by the four proposed models. For every power amplifier, the models’ performance was evaluated by calculating the adjacent channel leakage ratio (ACLR) and the normalized mean square error (NMSE). The proposed models were successful in linearizing the power amplifiers and showed a significant improvement in performance when compared to a RVFTDNN predistorter of the same size. All in all, the proposed models successfully reduced the number of coefficients of the predistorter while maintaining the performance.College of EngineeringDepartment of Electrical EngineeringMaster of Science in Electrical Engineering (MSEE
Efficient Dynamic Cost Scheduling Algorithm for Financial Data Supply Chain
No full textThe financial data supply chain is vital to the economy, especially for banks. It affects their customer service level, therefore, it is crucial to manage the scheduling of the financial data supply chain to elevate the efficiency of banking sectors’ performance. The primary tool used in the data supply chain is data batch processing which requires efficient scheduling. This work investigates the problem of scheduling the processing of tasks with non-identical sizes and different priorities on a set of parallel processors. An iterative dynamic scheduling algorithm (DCSDBP) was developed to address the data batching process. The objective is to minimize different cost types while satisfying constraints such as resources availability, customer service level, and tasks dependency relation. The algorithm proved its effectiveness by allocating tasks with higher priority and weight while taking into consideration customers’ Service Level Agreement, time, and different types of costs, which led to a lower total cost of the batching process. The developed algorithm proved effective by testing it on an illustrative network. Also, a sensitivity analysis is conducted by varying the model parameters for networks with different sizes and complexities to study their impact on the total cost and the problem under study