As a condition of graduation, KAUST requires master's students who complete a thesis to deposit it in the KAUST digital archive. Similarly, doctoral students must submit an electronic copy of their dissertation to the KAUST digital archive.

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  • Free Space Optics for 5G Backhaul Networks and Beyond

    Alheadary, Wael (2018-08)
    The exponential increase of mobile users and the demand for high-speed data services has resulted in signi cant congestions in cellular backhaul capacity. As a solution to satisfy the tra c requirements of the existing 4G network, the 5G net- work has emerged as an enabling technology and a fundamental building block of next-generation communication networks. An essential requirement in 5G backhaul networks is their unparalleled capacity to handle heavy tra c between a large number of devices and the core network. Microwave and optic ber technologies have been considered as feasible solutions for next-generation backhaul networks. However, such technologies are not cost e ective to deploy, especially for the backhaul in high-density urban or rugged areas, such as those surrounded by mountains and solid rocks. Addi- tionally, microwave technology faces alarmingly challenging issues, including limited data rates, scarcity of licensed spectrum, advanced interference management, and rough weather conditions (i.e., rain, which is the main weather condition that a ects microwave signals the most). The focus of this work is to investigate the feasibility of using free-space-optical (FSO) technology in the 5G cellular backhaul network. FSO is a cost-e ective and wide-bandwidth solution as compared to traditional backhaul solutions. However, FSO links are sensitive to atmospheric turbulence-induced fad- ing, path loss, and pointing errors. Increasing the reliability of FSO systems while still exploiting their high data rate communications is a key requirement in the de- ployment of an FSO backhaul network. Overall, the theoretical models proposed in this work will be shown to enhance FSO link performance. In the experimental direction, we begin by designing an integrated mobile FSO system. To the best of our knowledge, no work in the literature has addressed the atmospheric path loss characterization of mobile FSO channels in a coastal envi- ronment. Therefore, we investigate the impact of weather e ects in Thuwal, Saudi Arabia, over FSO links using outdoor and indoor setups. For the indoor experiments, results are reported based on a glass climate chamber in which we could precisely control the temperature and humidity.
  • Paving the Way for Efficient Content Delivery in Mobile Networks

    Lau, Chun Pong (2018-07-10)
    The flexibility of future mobile networks exploiting modern technologies such as cloud-optimized radio access and software-defined networks opens a gateway to deploying dynamic strategies for live and on-demand content delivery. Traditional live broadcasting systems are spectral inefficient. It takes up a lot more radio spectrum than that of mobile networks, to cover the same size of an area. Furthermore, content caching at base stations reduces network traffic in core networks. However, numerous duplicated copies of contents are still transmitted in the unicast fashion in radio access networks. It consumes valuable radio spectrum and unnecessary energy. Finally, due to the present of numerous mobile receivers with a wide diversity of wireless channels in a base station coverage area, it is a challenge to select a proper modulation scheme for video broadcasting to optimize the quality of services for users. In this thesis, the challenges and the problems in the current strategies for content delivery are addressed. A holistic novel solution is proposed that considers user preferences, user mobility, device-to-device communication, physical-layer resource allocation, and video quality prediction. First, a system-level scheduling framework is introduced to increase the spectral efficiency on broadcasting live contents onto mobile networks. It considers the audience preferences for allocating radio resources spatially and temporally. Second, to reduce the redundant transmissions in radio access networks, a content distribution system that exploits user mobility is proposed that utilizes the urban-scale user mobility and broadcasting nature of wireless communication for delay-tolerant large size content. Third, to further reduce the energy consumption in network infrastructure, a content distribution system that relies on both user mobility, and device-to-device communication is proposed. It leverages the mobile users as content carriers to offload the heavy mobile traffic from network-level onto device-level. Fourth, to mitigate the multi-user channel diversity problem, a cross-layer approach is deployed to increase the video quality for users especially for those who have a low signal-to-noise ratio signal. Finally, data mining techniques are employed to predict video qualities of wireless transmissions over mobile networks. The holistic solution has been empirically developed and evaluated. It achieves high spectral and energy efficiency and mitigates the video quality degradation in mobile networks.
  • Experimental Investigation on The Influence of Liquid Fuels Composition on The Operational Characteristics of The Liquid Fueled Resonant Pulse Combustor

    Qatomah, Mohammad (2018-07)
    In this study, the response of a liquid-fueled resonant pulse combustor to changes in liquid fuel composition was investigated. Experiments were performed with gasoline- ethanol, gasoline-diesel, and gasoline-heptane mixtures selected to produce meaningful variations in the ignition delay time. A review of ignition quality tester (IQT) data provided an expected increase in the overall delay for gasoline-ethanol mixtures with increasing ethanol concentrations, and a decrease for gasoline-diesel mixtures with increasing diesel concentrations in the mixture. By taking the phase of the ion signal as an indicator of heat release timing, the experimental results showed an agreement of gasoline-ethanol cases with the IQT data with a near linear increase with increasing ethanol concentrations. However, for gasoline-diesel, there exit no linear relation with the IQT data. For the case of gasoline-heptane mixtures, the results showed a linear decrease in delay with increasing heptane concentrations. Furthermore, it was shown that small changes in the physical properties of the fuel can significantly in sequence the cold-start operation of the combustor and alter the coupling between the unsteady heat release and resonant acoustic pressure wave during resonant operation. Dynamic combustion chamber pressure, stagnation temperature and pressure are recorded after a fixed warm-up time to characterize the performance and operation of the device. Results are interpreted in the context of fuel sensitivity and performance optimization of a resonant pulse combustor for pressure gain turbine applications.
  • Ecology of the Mangrove Microbiome

    Booth, Jenny (2018-07)
    Plants and animals have evolved unique morpho-physiological adaptions to cope with the harsh and steep environmental gradients that characterise the mangrove ecosystem. However, the capacity of these two main components of the system to thrive, and the extraordinary productivity of mangrove forests in extreme conditions, has been overlooked in terms of the role of the microbiome. By combining approaches that included molecular microbial ecology, biogeochemical analyses, microscopy, raman spectroscopy and microsensor measurements, this thesis aimed to investigate the potential role of bacterial symbiosis in the adaptation of mangrove crabs to their environment and subsequently how these different animals modify their environment. Finally, with a field-based approach monitoring microbial communities, sediment metabolism and plant performance, the thesis aimed to investigate the plant/animal/bacterial dynamics in relation to seasonal environmental changes to contribute to understand the mangrove plant productivity paradox of high productivity under conditions of limited nutrents. Crab species were associated with distinct gill-bacteria communities, that produced carotenoids, according with their level of terrestrial adaptation. These carotenoids may be involved in protecting the gills from oxidative stress during air exposure. The main groups of ecosystem engineering crabs in mangroves had significant but diverse effects on the sediment environment and microbiome predominantly related to their ecology (i.e. filter feeder vs herbivore). Burrows increase aerobic microbial activity in the immediate burrow wall with a cascade effect on sediment microbial communities and nutrient distribution observed consistently across mangroves in different locations and with diverse environmental conditions. Microorganisms play an important role in adapting crabs on their evolutionary path to land and could contribute to the success of their colonization. At high population densities, of more than 50 individuals per square meter in some mangroves, these crabs deeply impact the functioning of the mangrove ecosystem, affecting microbial networks and nutrient recycling in the sediment, which may ameliorate conditions for plant growth. The microbiome is an understudied component of mangroves that lies at the basis of the functioning of these systems, influencing the success of the animal inhabitants (ecosystem engineers) that deeply modify the sediment microbiome, therefore influencing ecosystem functioning and resilience and, potentially, the success of the plants themselves (ecosystem architects).
  • Single molecule analysis of the diffusion and conformational dynamics

    Abadi, Maram (2018-07)
    Spatial and temporal dynamics of polymer chains play critical roles in their rheological properties, which have a significant influence on polymer processing and fabrication of polymer-based (nano) materials. Many theoretical and experimental studies have aimed at understanding polymer dynamics at the molecular level that give rise to its bulk phase properties. While much progress has been made in the field over the past ~60 years, many aspects of polymers are still not understood, especially in complicated systems such as entangled fluids and polymers of different topologies. In addition, the physical properties of biological macromolecules, i.e. DNA, are expected to affect the spatial organization of chromosome in a cell, which has the potential impact on a broad epigenetics research. Here, we propose new methods for simultaneous visualization of diffusive motion and conformational dynamics of individual polymer chains, two most important factors that characterize polymer dynamics, based on a new single-molecule tracking technique, cumulative-area (CA) tracking method. We demonstrate the applicability of the CA tracking to the quantitative characterization of the motion and relaxation of individual topological polymer molecules under entangled conditions, which is possible only by using the newly-developed CA tracking, using fluorescently-labeled linear and cyclic dsDNA as model systems. We further extend the technique to multi-color CA tracking that allows for the direct visualization and characterization of motion and conformation of interacting molecules. We also develop a new imaging method based on recently developed 3D super-resolution fluorescence microscopy technique, which allows direct visualization of nanoscale motion and conformation of the single molecules that is not possible by any other methods. Using these techniques, we investigate spatial and temporal dynamics of polymers at the single-molecule level, with special emphasis on the effect of topological forms of the molecules and the confined geometry on their spatiotemporal dynamics. Our results demonstrate that the new methods developed in this thesis provide an experimental platform to address key questions in the entangled topological polymer dynamics. The research will provide a platform for developing new polymer-based materials and open the possibility of studying spatial organization of DNA in a confined geometry from physics point of view.
  • Investigation of the Effect of Operational Parameters on the Fouling Development and Control in an Algal Membrane Photobioreactor for the Treatment of Simulated Secondary Wastewater

    Lamprea Cala, Andres (2018-07)
    The release of water effluents rich in nutrients such as nitrogen and phosphorus without adequate treatment represents environmental and human health concerns. Growing concerns about these impacts have resulted in increasingly stringent water quality regulations that encouraged the adoption of advanced treatment processes. Microalgae-based advanced wastewater treatment has gained momentum owing to its well-known advantages for advanced wastewater treatment, including the recovering of nutrients for the production of fertilizers, biofuels and fine chemical from microalgal biomass. Nevertheless, the progressive membrane fouling and permeate flux declining hamper the large-scale commercialization of membrane photobioreactors (MPBRs) in the wastewater sector. In order to get a further understanding of the fouling mechanisms and antifouling control strategies, this study investigated the effect of the hydraulic retention time on the fouling development, and the effect of different physical fouling control strategies in the fouling mitigation. A synthetic secondary effluent was continuously fed to three MPBRs operated at different HRTs (12, 24 and 36 hours). Different fouling behaviors were found as the HRT changed, which was confirmed by continuously monitoring the transmembrane pressure (TMP) and by measurements in the biomass and its algal organic matter (AOM) properties. Lowering the HRT resulted in higher fouling rates due to changes in the biomass and AOM properties. Higher HRTs led to lower fouling rates and to a lower organic rejection across the membrane. The retention of small-MW organics in SMPBR12h was found to exacerbate the fouling resistance, whereas the accumulation of large-MW biopolymers enhanced the rejection of organics, despite of not imparting significant resistance in SMPBR24h. In order to assess the impact of different physical fouling control strategies, namely relaxation, backwash and air scouring, OCT in-situ monitoring was employed in MPBR12h to provide real-time information of the fouling layer properties (thickness and relative roughness) and its interaction with the membrane surface. Different fouling mechanisms were observed under different fouling control strategies. MPBRRLX and MPBRBW presented similar fouling rates despite of the lower permeate productivities of the latter. The lowest fouling rates were observed in MPBRSC, where stronger interactions between the membrane and small-MW organics and particles was observed.
  • Mechanism Design for Virtual Power Plant with Independent Distributed Generators

    Kulmukhanova, Alfiya (2018-07)
    We discuss a model of a virtual power plant (VPP) that provides market access to privately-owned distributed generations (DGs). The VPP serves passive loads, processes bids from generators, and trades in the wholesale market. The generators can be renewable or thermal, and they act strategically to maximize their own profit. The VPP establishes the rules of the internal market to minimize the cost of energy and the cost of balancing while ensuring generator participation and load balancing. We derive a heuristic mechanism for internal market and propose a dynamic programming approach for minimizing the VPP cost. We present illustrative simulations for both single and multistage market bidding and then compare the resulting performance to the centralized VPP model, where the DGs are assumed to be owned by the VPP. We show that the proposed design incentivizes the DG agents to behave the same as in the centralized case, but the optimal cost paid by VPP is higher due to the payments to the DG owners.
  • Indoor Localization Using Three dimensional Multi-PDs Receiver Based on RSS

    Liu, Yinghao (2018-07)
    In modern life, there are many applications where positioning plays an important role. People have developed the global positioning system (GPS) to locate world wide position with error in decameter scales, which brings people much convenience. However, the accuracy of GPS is too low for indoor localization. The signals will drop down due to the signal attenuation caused by construction materials. With the well-developed GPS being indispensable for outdoor activities, many researchers have been also devoted to seeking an indoor positioning system to realize indoor localization with acceptable error. Indoor localization can be very useful in different situations, like locating, tracking, navigation and identification. For example, in the mall, locating the exact goods for customers can provide much convenience and benefits. Locating and tracking in the airport can greatly help passengers save their time and energy in reaching the destination. In another general scenario of identification, the population of observed targets is usually larger than just one. Hence, only with small error, indoor localization system (ILS) can be able to identify the targets despite the neighbors. Due to the emerging and urging demands of increasing the accuracy of indoor localization, we propose a novel design of three dimensional (3-D). optical receiver for visible light communication (VLC) indoor positioning system. First, we model the optical wireless channel. Then we utilize modified triangulation method to obtain more robust receiver position by using at least two light-emitting diodes (LEDs) and one receiver consisting of nine photodetectors (PDs). Finally, the improved algorithm is implemented and the results are shown under our three dimensional multiple photodetectors (multi-PDs) structure receiver. In the simulation, we take the parameters of Lambertian radiation pattern, LEDs and PDs as those shown in [1] . To be noticed, our design of multi-PDs receiver is fully expanded into three dimensions compared with the pyramid receiver (PR), which allows indoor positioning with our receiver structure to be more robust to the higher or corner positions. The details will be explained in the following sections. Based on Multiple-Photodiodebased Indoor Positioning algorithm [1], the indoor positioning algorithm is improved by redefining the optimization problem of obtaining the direction from receiver to LED and using weighted triangulation method to locate receiver position. We admit the solution under the redefined problem is not optimal to the actual problem. Yet, our given solution is better to that in [1] due to the existence of noise, which is reasonable and has been verified.
  • Diversity, ecology, and biotechnological potential of microorganisms naturally associated with plants in arid lands

    Mosqueira Santillán, María José (2018-07)
    Plants naturally host complex microbial communities in which the plant and the symbiotic partners act as an integrated metaorganism. These communities include beneficial (i.e. plant growth promoting, PGP) microorganisms which provide fundamental ecological services able to enhance host plant fitness and stress tolerance. PGP microorganisms represent a potential bioresource for agricultural applications, especially for desert farming under the harsh environmental conditions occurring in hot/arid regions (i.e. drought and salinity). In this context, understanding the ecological aspects of the associated microorganisms is crucial to take advantage of their ecological services. Here, hot/desert ecosystems were selected and two contrasting plant categories were used as models: (i) wild plants (i.e. speargrasses) growing in hot-desert sand dunes and (ii) the main crop cultivated in desert ecosystems, the date palm. By using highthroughput DNA sequencing and microscopy, the ecology and functionality of the microbial communities associated with these plants were characterized. Additionally, the PGP services of bacteria isolated from date palm were explored. I found that the harsh conditions of the desert strongly affect the selection and assembly of microbial communities associated with three different speargrass species, determining a plant species-independent core microbiome always present among the three plant species and carrying important PGP traits. On the contrary, in agroecosystems where desert farming practices are used, the plant species, i.e. date palm exerts a stronger selective pressure than the environmental and edaphic factors favoring the recruitment of conserved microbial assemblages, independent of the differences in the soil and environmental conditions among the studied oases. Such selective pressure also favors the recruitment of conserved PGP microorganisms (i.e. Pseudomonas sp. bacterial strains) able to protect their host from salinity stress through the induction of root architectural changes regulated by the modification of the root system auxin homeostasis. Overall, we found that deserts are unique ecosystems that challenge the paradigm of microbial community assembly, as it was defined from studies in non-arid ecosystems. The understanding of the ecological features regulating the ecological properties of such unique microbial community assembly will be a key-step to improve the chances of successful application of ‘PGP microorganisms’ in arid agroecosystems.
  • Scalable Discovery and Analytics on Web Linked Data

    Abdelaziz, Ibrahim (2018-07)
    Resource Description Framework (RDF) provides a simple way for expressing facts across the web, leading to Web linked data. Several distributed and federated RDF systems have emerged to handle the massive amounts of RDF data available nowadays. Distributed systems are optimized to query massive datasets that appear as a single graph, while federated systems are designed to query hundreds of decentralized and interlinked graphs. This thesis starts with a comprehensive experimental study of the state-of-the-art RDF systems. It identifies a set of research problems for improving the state-of-the-art, including: supporting the emerging RDF analytics required by many modern applications, querying linked data at scale, and enabling discovery on linked data. Addressing these problems is the focus of this thesis. First, we propose Spartex; a versatile framework for complex RDF analytics. Spartex extends SPARQL to seamlessly combine generic graph algorithms with SPARQL queries. Spartex implements a generic SPARQL operator as a vertex-centric program that interprets SPARQL queries and executes them efficiently using a built-in optimizer. We demonstrate that Spartex scales to datasets with billions of edges, and is at least as fast as the state-of-the-art specialized RDF engines. For analytical tasks, Spartex is an order of magnitude faster than existing alternatives. To address the scalability limitation of federated RDF engines, we propose Lusail; a scalable system for querying geo-distributed RDF graphs. Lusail follows a two-tier strategy: (i) locality-aware decomposition of the query into subqueries to maximize the computations at the endpoints and minimize intermediary results, and (ii) selectivity-aware execution to reduce network latency and increase parallelism. Our experiments on billions of triples show that Lusail outperforms existing systems by orders of magnitude in scalability and response time. Finally, enabling discovery on linked data is challenging due to the prior knowledge required to formulate SPARQL queries. To address these challenges; we develop novel techniques to (i) predict semantically equivalent SPARQL queries from a set of keywords by leveraging word embeddings, and (ii) generate fine-grained and non-blocking query plans to get fast and early results.
  • Entropy Stability of Finite Difference Schemes for the Compressible Navier-Stokes Equations

    AlSayyari, Mohammed (2018-07)
    In this thesis, we study the entropy stability of the compressible Navier-Stokes model along with a modification of the model. We use the discretization of the inviscid terms with the Ismail-Roe entropy conservative flux. Then, we study entropy stability of the augmentation of viscous, heat and mass diffusion finite difference approximations to the entropy conservative flux. Additionally, we look at different choices of the diffusion coefficient that arise from combining the viscous, heat and mass diffusion terms. Lastly, we present numerical results of the discretizations comparing the effects of the viscous terms on the oscillations near the shock and show that they preserve entropy stability.
  • Potential of Bacterial Volatile Organic Compounds for Biocontrol of Fungal Phytopathogens and Plant Growth Promotion Under Abiotic Stress

    Soussi, Asma (2018-07)
    Bacterial volatile organic compounds (VOCs) are signal molecules that may have beneficial roles in the soil-plant-microbiome ecosystem. In this Ph.D. thesis, I aimed to assess and characterize the role of bacterial VOCs in plant tolerance to drought and in the biocontrol of fungal pathogens. I started by studying two root endophytic bacteria isolated from pepper plants cultivated under desert farming conditions. They showed an enhancement of pepper tolerance to drought stress and an amelioration of its physiological status. Moreover, they induced the expression of a vacuolar pyrophosphatase proton pump (V-PPase), implicated in the regulation of the vacuolar osmotic pressure, facilitating water uptake. Besides, the exposure of Arabidopsis thaliana plants, grown under salinity stress, to the volatile 2,3-butanediol, described for its plant growth promotion (PGP) potential, enhanced the plants tolerance to salinity, proving the potential involvement of this volatile in the osmotic stress resistance mechanism. Then, I studied VOCs released by three bacteria associated to healthy rice plants. Their released VOCs mixtures modified the color pattern of Magnaporthe oryzae, the agent of the rice blast disease, and protected rice from the pathogen infection. A significant reduction of melanin production, sporulation and appressoria formation was measured in presence of the bacterial VOCs, without major effects on mycelial proliferation. 1-butanol-3-methyl, one of the nine VOCs co-produced by the studied bacteria, proved its potential of reducing M. oryzae melanin in vitro. In vivo tests confirmed the infection inhibition effects mediated by the rice-bacterial VOCs, with a reduction of 94% of the disease incidence. Lastly, I compared the genomes of the five bacteria considered in the previous experimental studies. The PGP traits and the VOCs pathways identified from the genome analyses confirmed the effects observed with the in vitro and in vivo assays, revealing a complex mode of promotion and protection offered by the studied plant-associated bacteria. In conclusion, plant-associated bacterial VOCs can play potentially important roles in modulating plant drought tolerance and reducing fungal virulence. Such biological resources represent novel tools to counteract the deleterious effects of abiotic and biotic stresses and have the potential to be exploited for sustainable approaches in agriculture.
  • Towards macroscopic modeling of electro-thermo-mechanical couplings in PEDOT/PSS: Modeling of moisture absorption kinetics

    Zhanshayeva, Lyazzat (2018-07)
    Organic conducting polymer, poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDOT:PSS), is widely recognized for its electro-actuation mechanism and is used in flexible electronics. Its high potential as actuator is based on a strong coupling between chemical, mechanical and electrical properties which directly depends on external stimuli. There is no model today to describe the interplay between moisture absorption, mechanical expansion and electrical stimulus. Elucidating the role of each component in the effective actuation properties is needed to further optimize and tailor such materials. The objective of this thesis is to develop a macroscopic model to describe water sorption kinetics of the PEDOT:PSS film. We used gravimetric analysis of pure PEDOT:PSS film of three different thicknesses to investigate absorption kinetics over a broad range of temperatures and relative humidity. Our results revealed that the moisture uptake of PEDOT:PSS film does not follow Fickian diffusion law due to the retained amount of water after desorption process. We used an existing diffusionreaction model to describe this behavior, and COMSOL Multiphysics and MATLAB software programs to implement it. We observed that the generic model we used in our work could predict polymer behavior with 95% accuracy. However, our model was not able to properly represent the data at very high relative humidity at low temperature, which was attributed to the excessive swelling of the film. Also, we examined a relation between the moisture content of PEDOT:PSS and its mechanical strain and electrical conductivity. The results presented here are the first step towards a general multiphysics electro-thermo-mechanical description of PEDOT:PSS based actuators.
  • Molecular Fingerprinting to Understand Diazotrophic Microbe Distribution in Oligotrophic Oceans

    MOHAMED, ROSLINDA (2018-07)
    In oligotrophic systems, where primary production is low and nitrogen is in short supply, nitrogen fixation process is intense. Although a few diazotrophs (eg. Trichodesmium) have been widely-studied, the rest of the diazotrophic community is still poorly understood. Furthermore, the global distribution of diazotrophs are yet to be clearly resolved. This dissertation assessed the distribution of diazotrophs in oligotrophic systems, particularly in the tropical and subtropical oceans, using genomics tools including next-generation sequencing. We first tested out a pair of nifH-specific primer that previously performed well in silico, but found that its application on seawater samples was biased towards paralogous, non-functional nitrogenase nifH genes. Instead, we found that the use of a nested PCR method using different primers sets to be more effective in amplifying functional nifH genes. Trichodesmium sp., UCYN-A and Pseudomonas sp. forms the core of the diazotrophic communities in oligotrophic oceans. Temperature is the primary driver of the abundances and distributions of these organisms in the Pacific, Atlantic and Indian Oceans, as well as in the oligotrophic Red Sea. Trichodesmium tends to dominate warm, surface waters, while UCYN-A prefers cooler environments and dwell in sub-surface waters in the Red Sea. Due to the dominance of Pseudomonas in the large-sized fraction samples, they are believed to be part of the Trichodesmium-associated consortia, although this requires further investigations. We also found non-cyanobacterial species of diazotrophs to be dominant previously-described hotspots of nitrogen fixation, and found evidence for the widespread of alternative nitrogenases (Cluster II). Using the Red Sea as an exemplar for future warming ocean, we found patterns of niche partitioning in the Red Sea diazotrophs, based on their distribution along seasons, latitude and depth. Our one-year observation of Red Sea Trichodesmium population witnessed the collapse of the population at temperatures above 32°C. This dissertation not only improve our understanding of the effects of future rising temperature on the natural populations of diazotrophs, but it also helps to establish a baseline understanding of the structure, spatial and temporal dynamics of Red Sea diazotrophs, which has not been discussed elsewhere.
  • Real-Time and Ultra-High De finition Video Transmission in Underwater Wireless Optical Networks

    Al-Halafi, Abdullah (2018-07)
    Oceans form about three quarters of our planet Earth, and house immense resources that are critical for future generations. Exploring and monitoring such resources is becoming essential to protect the effected ones by the irresponsible human behavior, and to discover new ones. The limitations of depths mandate the search for alternatives and where human divers become endangered. Using remotely operated vehicles is commonly used for marine explorations, while tethered to ships. To be fully autonomous and to avoid damaging the fragile marine environment, they must be equipped with wireless communication solutions that enable real-time control and feedback on their maneuvering and mobility. Also, the ultimate tool to monitor, inspect and repair underwater structures is to use video streaming to mimic the reality of those unseen parts of the world. Existing underwater communications do not provide the necessary features to transmit video from the deep. Acoustic waves as well as the radio frequency waves are either limited in bandwidths or strongly attenuated by the water medium. On the other hand, wireless optical communication is an emerging technology that provides high transmission speeds and can enable video streaming underwater. This motivates bringing wireless optical technologies for real-time video streaming underwater to a practical implementation by undertaking theoretical and experimental studies of systems and techniques that can provide optimized solutions within our proposed framework. We present our video transmission architecture that facilitates programmable system configurations. Software defined platforms provide us with the means of configuring several setups to test our approach. In order to fully utilize the available optical spectrum, we have additionally implemented several modulation techniques in various laboratory scenarios. Real-time and ultra-high definition video has been successfully demonstrated. The overall system performance and throughput analysis have been provided. A thorough investigation of the system performance under various underwater channel conditions was undertaken. Also, as the delay resulting from queuing, when video packets are waiting for service, is key in time critical applications, we derive the mathematical model and investigate the delay effects and the packet dropping probability on the overall system performance when our setup is extended to a multi-channel configuration.
  • Design of a Hydraulic Variable Compression Ratio Piston for a Heavy Duty Internal Combustion Engine

    Al Mudraa, Sultan (2018-07)
    A High percentage of fuel consumption worldwide is in internal combustion engines which has led environmental organizations and authorities to put further pressure on the engine industries to reduce CO2 emissions and enhance engine efficiency. However, historically, the effect of the compression ratio on increasing thermal efficiency of the engine is well known, hence; numerous technical solutions have been proposed to implement a variable compression ratio concept. A new first-class engineering solution to use a hydraulic piston was initially patented by BICERA (British Internal Combustion Engine Research Association) , then improved by Continental and Daimler Benz. A Hydraulic variable compression ratio piston is a hydraulically actuated piston that provides a practical method of obtaining a variable compression ratio piston. In this literature, a hydraulic variable compression ratio piston for a Volvo D13 diesel engine was designed, analyzed, modeled and discussed. This analysis was accomplished by first performing kinematic and dynamic analyses for the piston motion and acceleration based on the crank-slider mechanism. Following this the oil flow characteristics were defined in every mechanical element transferring the oil in its journey from the engine pump to the piston. Moreover, two different designs were proposed in an attempt to predict the compression ratio by modeling the hydraulic, dynamic and engine execution simultaneously. Additionally, stress on the piston was analyzed using Finite Element Analysis (FEA) to assure piston sustainment and rigidity against the harsh combustion chamber environment. In conclusion, the best design was successfully selected and finalized to reach a wide compression ratio range under a boosted inlet pressure based on the selected design, dimensions, check valves and relief valves.
  • First principles based fuel design: investigating fuel properties and combustion chemistry

    Ahmed, Ahfaz (2018-07)
    Advanced combustion engine concepts require fuels which are meticulously designed to harness full potential of novel engine technologies. To develop such fuels, better understanding of fuel properties and their effect on combustion parameters is needed. The investigations reported in this work establishes relationships between several fuel properties and combustion parameters at engine relevant conditions. Further, these findings along with conclusions from other studies are utilized to synthesize fuels and surrogate fuels with tailored combustion properties. This approach of designing fuels relies on constrained non-linear optimization of several combustion properties simultaneously to design surrogate fuels for transportation fuels to enable combustion simulations. This scheme of fuel design has been devised and presented as Fuel Design Tool in Ahmed et al. Fuel 2015. Detailed investigations have been made to understand the effect of fuel properties on the ignition of fuels in Rapid compression machines utilizing a custom built multi-zone model. The study was further extended to explore fuel effects on engine combustion utilizing experiments and modelling to gather understanding of instances of engine knocking and pollutant formation. Bio-blended fuels allow mitigation of harmful pollutants and also enables engines to operate at higher efficiency. Ignition characteristics of two high octane bio-blended gasolines were studied experimentally in rapid compression machine and shock tube and detailed chemical kinetic analysis was conducted to understand how the presence of biofuels (i.e., ethanol) in gasoline influences the evolution of important radicals controlling ignition. Another set of biofuels namely methyl acetate and ethyl acetate were studied employing fundamental experimental and computational methods. The investigation involved development and analysis of combustion chemistry models, speciation studies in jet stirred reactors, ignition delay measurements and determination of laminar burning velocities. These fuels are found suited for high performance advanced spark ignition engines and the developed model and analysis will lead to optimization of combustion performance. The developed fuel design tool along with enhanced understanding of combustion chemistry and fuel properties enables a complete toolkit ready to be utilized to develop fuels with better suited properties for the advanced combustion modes.
  • On the role of thermal fluctuations in fluid mixing

    Narayanan, Kiran (2018-07)
    Fluid mixing that is induced by hydrodynamic instability is ubiquitous in nature; the material interface between two fluids when perturbed even slightly, changes shape under the influence of hydrodynamic forces, and an additional zone called the mixing layer where the two fluids mix, develops and grows in size. This dissertation reports a study on the role of thermal fluctuations in fluid mixing at the interface separating two perfectly miscible fluids of different densities. Mixing under the influence of two types of instabilities is studied; the Rayleigh-Taylor (RTI) and Richtmyer-Meshkov (RMI) instabilities. The study was conducted using numerical simulations after verification of the simulation methodology. Specifically, fluctuating hydrodynamic simulations were used; the fluctuating compressible Navier-Stokes equations were the physical model of the system, and they were solved using numerical methods that were developed and implemented in-house. Our results indicate that thermal fluctuations can trigger the onset of RTI at an initially unperturbed fluid-fluid interface, which subsequently leads to mixing of multi-mode character. In addition we find that for both RMI and RTI, whether or not thermal fluctuations quantitatively affect the mixing behavior, depends on the magnitude of the dimensionless Boltzmann number of the hydrodynamic system in question, and not solely on its size. When the Boltzmann number is much smaller than unity, the quantitative effect of thermal fluctuations on the mixing behavior is negligible. Under this circumstance, we show that mixing behavior is the average of the outcome from several stochastic instances, with the ensemble of stochastic instances providing the bounds on mixing-related metrics such as the mixing width. Most macroscopic hydrodynamic systems fall in this category. However, when the system is such that the Boltzmann number is of order unity, we show that thermal fluctuations can significantly affect the mixing behavior; the ensemble-averaged solution shows a departure from the deterministic solution. We conclude that for such systems, it is important to account for thermal fluctuations in order to correctly capture their physical behavior.
  • Exploration of Low-Cost, Natural Biocidal Strategies to Inactivate New Delhi Metallo-beta-lactamase (NDM)-Positive Escherichia coli PI-7, an Emerging Wastewater-Contaminant

    Aljassim, Nada I. (2018-07)
    Conventional wastewater treatment plants are able to reduce contaminant loads within regulations but do not take into account emerging contaminants. Antibiotic resistance genes and antibiotic resistant bacteria have been shown to survive wastewater treatment and remain detectable in effluents. The safety of treated wastewaters is crucial, otherwise unregulated and unmitigated emerging contaminants pose risks to public health and impede wastewater reuse. This dissertation aimed to further understanding of emerging microbial threats, and tested two natural and low-cost tools for their mitigation: sunlight, and bacteriophages. A wastewater bacterial isolate, named E. coli PI-7, which is highly antibiotic resistant, carries the novel antibiotic resistance gene New Delhi metallo-beta-lactamase NDM-1 gene, and displays pathogenic traits, was chosen to model responses to the treatments. Results found that solar irradiation was able to achieve a 5-log reduction in E. coli PI-7 numbers within 12 hours of exposure. However, the results also emphasized the risks from emerging microbial contaminants since E. coli PI-7, when compared with a non-pathogenic strain E. coli DSM1103 that has less antibiotic resistance, showed longer survival under solar irradiation. In certain instances, E. coli PI-7 persisted for over 6 hours before starting to inactivate, exhibited complex stress resistance gene responses, and activated many of its concerning pathogenicity and antibiotic resistance traits. However, upon solar irradiation, gene expression results obtained from both E. coli strains also showed increased susceptibility to bacteriophages. Hence, bacteriophages were coupled with solar irradiation as an additional mitigation strategy. Results using the coupled treatment found reduced cell-wall and extracellular matrix production in E. coli PI-7. DNA repair and other cellular defense functions like oxidative stress responses were also impeded, rendering E. coli PI-7 more susceptible to both stressors and successfully hastening the onset of its inactivation. Overall, the dissertation is built upon the need to develop strategies to further mitigate risks associated with emerging microbial contaminants. Solar irradiation and bacteriophages demonstrate potential as natural and low-cost mitigation strategies. Sunlight was able to achieve significant log-reductions in tested E. coli numbers within a day’s exposure. Bacteriophages were able to overwhelm E. coli PI-7’s capacity to resist solar inactivation while not affecting the indigenous microbiota.
  • Synthesis and Application of PN3P Cobalt Pincer Complex for Selective Hydrogenation of Nitriles to Secondary Imines and α -Alkylation of Nitriles with Alcohols

    Al Dakhil, Abdullah (2018-07)
    Pincer complexes moieties have attracted much attention in the past years. They have been proved that they are highly active catalysts in many different known transition metal-catalyzed organic reaction and some unpredictable organic transformation. In this thesis, we will use PN3P Cobalt pincer complex in two different applications. The first application is the unpresented Cobalt-catalyzed hydrogenation of nitriles to secondary imines. The selective hydrogenation of nitriles into secondary imines is a very challenging task and the catalysts play a very important role in the reaction and the selectivity. Herein in the thesis, we report the first selective hydrogenation of nitriles to secondary imines catalyzed by a well-defined and accessible PN3P cobalt pincer complex. Our results show different selectivity compared with the known PNP cobalt catalytic system during the nitriles hydrogenation. A set of aliphatic and aromatic nitriles are hydrogenated to the secondary imine under relatively mild conditions. The second application is the alkylation of nitriles with alcohols using PN3P cobalt pincer complex. The alcohol is being used here as alkylating agent in state of using toxic alkyl halides or excess amount of base to avoid any salt waste. The cobalt pincer complex work as catalyst for transformation that undergoes alkylation via hydrogen transfer pathways. The beauty of this reaction that it is delver water as the only byproduct. A different nitriles and alcohol are tolerated in this reaction.

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