Recent Submissions

  • Toward Improving the Internet of Things: Quality of Service and Fault Tolerance Perspectives

    Alaslani, Maha S. (2021-04-13) [Dissertation]
    Advisor: Shihada, Basem
    Committee members: Alouini, Mohamed-Slim; Zhang, Xiangliang; Bessani, Alysson
    The Internet of Things (IoT) is a technology aimed at developing a global network of machines and devices that can interact and communicate with each other. Supporting IoT, therefore, requires revisiting the Internet's best e ort service model and reviewing its complex communication patterns. In this dissertation, we explore the unique characteristics of IoT tra c and examine IoT systems. Our work is motivated by the new capabilities o ered by modern Software De ned Networks (SDN) and blockchain technology. We evaluate IoT Quality of Service (QoS) in traditional networking. We obtain mathematical expressions to calculate end-to-end delay, and dropping. Our results provide insight into the advantages of an intelligent edge serving as a detection mechanism. Subsequently, we propose SADIQ, SDN-based Application-aware Dynamic Internet of things QoS. SADIQ provides context-driven QoS for IoT applications by allowing applications to express their requirements using a high-level SQL-like policy language. Our results show that SADIQ improves the percentage of regions with an error in their reported temperature for the Weather Signal application up to 45 times; and it improves the percentage of incorrect parking statuses for regions with high occupancy for the Smart Parking application up to 30 times under the same network conditions and drop rates. Despite centralization and the control of data, IoT systems are not safe from cyber-crime, privacy issues, and security breaches. Therefore, we explore blockchain technology. In the context of IoT, Byzantine fault tolerance-based consensus protocols are used. However, the blockchain consensus layer contributes to the most remarkable performance overhead especially for IoT applications subject to maximum delay constraints. In order to capture the unique requirements of the IoT, consensus mechanisms and block formation need to be redesigned. To this end, we propose Synopsis, a novel hierarchical blockchain system. Synopsis introduces a wireless-optimized Byzantine chain replication protocol and a new probabilistic data structure. The results show that Synopsis successfully reduces the memory footprint from Megabytes to a few Kilobytes with an improvement of 1000 times. Synopsis also enables reductions in message complexity and commitment delay of 85% and 99.4%, respectively.
  • Programmable materials for sensors, actuators and manipulators for soft robotics applications

    Chellattoan, Ragesh (2021-04) [Dissertation]
    Advisor: Lubineau, Gilles
    Committee members: Lacoste, Deanna; Blilou, Ikram; Leng, Jinsong
    This thesis describes the concept of programmable materials with tunable physical properties applicable to soft robots. We present these materials for three major applications in soft robotics: sensing, actuation, and robotic manipulation. The strain sensors recognize the internal stimuli in a soft robot, whereas the conductors collect the sensors’ signals to the control part. In the first part, we want to develop both stretchable strain sensors and conductors from a single material by programming a nanowire network’s electrical property, which we achieve through Electrical Welding (e-welding). We demonstrate the transformation of a Silver Nanowire (AgNW)-polymer sponge from a strain sensor to a stretchable conductor through e-welding. Using this method, we produced a soft hybrid e-skin having both a sensor and conductor from a single material. In the second part, we propose new active actuation solutions by obtaining quick, tunable pressure inside a soft material that we achieve through a liquid-gas phase transition of a stored liquid using an efficient electrode. We discuss the significant design variables to improve the performance and propose a new design for the electrodes, for enhancing actuation speed. We propose using low voltage equipment to trigger the phase transition to produce compact actuation technology for portable applications. Using this method, we produced a portable soft gripper. In the third and last part, we want to develop a simple robotic manipulation technology using a single-chambered soft body instead of a multi-chambered system. We propose using on-demand stiffness change in soft material to control the shape change of a single-chambered soft body. For this, we introduce a new concept of a stiffness tunable hybrid fiber: a fiber with stiff and soft parts connected in a series. We demonstrate a substantial change in membrane stiffness in the fiber through locking/unlocking of the soft part of the fiber. We integrated these fibers into a pneumatically operated single-chambered soft body to control its stiffness for on-demand shape change. If applied together, these three concepts could result in a fully printable, cheap, light, and easily controllable new generation soft robots with augmented functionalities.
  • Generation of Orbital Angular Momentum (OAM) Modes with a Spiral Phase Plate Integrated Laser Source

    Stegenburgs, Edgars (2021-04) [Dissertation]
    Advisor: Ooi, Boon S.
    Committee members: Alouini, Mohamed-Slim; Liberale, Carlo; Forbes, Andrew
    The objective of this work is to develop a near-infrared laser device capable of emitting orbital angular momentum (OAM) light. The prototyped device must be suitable for compact, energy-saving optical communication applications. Integrated OAM lasers will revolutionize high-capacity data transmission over any telecommuni- cation network environment, as OAM light can be guided and transmitted through kilometers of optical fibers and propagated in free space and underwater. Several methods for generating OAM light employing various complex monolithic and hybrid integration methods have been demonstrated. In this work, microscale integrated spiral phase plates (SPPs) are chosen to convert the laser beam output into an OAM mode. The concept and design fundamentals of SPPs are discussed, followed by the SPP fabrication process and their implementation in a high-speed communication setup and then integration with a semiconductor laser. SPPs are fabricated by a novel direct laser writing that provides the possibility to rapidly prototype 3D photonic structures via a two-photon polymerization pro- cess. After fabrication, SPPs are used in a fine-tuned free-space optical experimental setup that requires high-precision intercomponent alignment to test the high-speed OAM communication system and analyze the quality of OAM modes, resulting in high-purity OAM signals at data rates up to 1.8 Gbit/s – limited by the avalanche photodetector (APD) frequency response. The fabricated 20-μm-diameter SPPs were the smallest reported in the literature to date for optical characterization. A proof-of-concept monolithic light-emitting array, as a highly integrated OAM laser source, is further proposed for telecommunications and other applications. SPP-integrated 940-nm vertical-cavity surface-emitting laser (VCSEL) array chips that are relatively low-cost, have a small footprint, and are manufacturable in high volumes are developed. SPPs with topological charge modulus values from 1 to 3 are fabricated on the VCSEL arrays, demonstrating OAM modal purities up to ∼65%. The experimentally evaluated data rates in the OAM setup showed consistently sta- ble links up to 2.0 Gbit/s with a bit error ratio of ∼ 1.6 × 10−8 (APD-limited). The challenges of SPP-laser integration are summarized, with the conclusion that the widespread adoption of OAM is limited by the availability of practical integrated solutions for OAM generation and detection.
  • Experimental and theoretical study of PAH and incipient soot formation in laminar flames

    Li, Zepeng (2021-04) [Dissertation]
    Advisor: Roberts, William L.
    Committee members: Lacoste, Deanna; Chung, Suk Ho; Knio, Omar; Thomson, Murray J.
    Emissions of soot and polycyclic aromatic hydrocarbons (PAHs) from incomplete burning of hydrocarbon fuels pose a great threat to the environment and human health. To reduce such emissions, a comprehensive understanding of their evolution process is essential. In this work, a series of research studies were conducted to evaluate sooting tendencies and to experimentally and theoretically develop PAH mechanisms. The sooting tendencies of oxygenated fuels were quantitively investigated in counterflow diffusion flames. Sooting limits are described by critical fuel and oxygen mole fractions, measured with a laser scattering technique. The addition of dimethyl ether displays non-monotonic behavior on sooting tendencies at elevated pressures, which is attributed to the chemical effect from kinetic simulations. The tendency of incipient soot formation of other oxygenated fuels (e.g., alcohol, acid, ether, ketone, and carbonate ester) was also assessed, using a similar approach. As the precursor of soot, PAH measurement using laser induced fluoresecnce was implemented to track the evolution processes from PAHs to incipient soot. Developing a PAH mechanism is essential to the understanding of soot formation; however, PAH formation and its growth process are not well understood. Based on previous research, PAHs with 5-membered rings are abundant in flames. Therefore, the growth of PAHs with 5-membered rings was investigated, using acenaphthylene (A2R5) as the example. The density functional theory (DFT) and the transition state theory (TST) were adopted to calculate potential energy surfaces and reaction rate coefficients. The existence of 5-membered rings appreciably impacts PAH production by facilitating the formation of planar PAHs with C2H substitution, thereby improving existing PAH mechanisms. In PAH mechanisms, the thermochemistry properties are not all calculated, but are hypothesized to be equal to those of a similar structure. The simulation accuracy of the hypothesis is explored here by discussing the sensitivity of the thermochemistry parameters in flame simulations. The group additivity method utilizing THERM codes is used to calculate thermochemistry properties. PAH loading affects the sensitivity of thermochemistry properties to both flame temperature and product yields. These results show that either accurate thermochemistry properties, or reverse reaction rates should be provided in the mechanism to improve simulation accuracy.
  • Broadband Elastic Wave Propagation in Intact Rocks (Quasi-static to MegaHertz)

    Perbawa, Andika (2021-04) [Dissertation]
    Advisor: Santamarina, Carlos
    Committee members: Hoteit, Ibrahim; Santamarina, Carlos; Finkbeiner, Thomas; Lubineau, Gilles; Cascante, Giovanni
    Elastic wave propagation in saturated porous rocks reflects the fluid and mineral stiffness and their frequency-dependent interaction. Seismic imaging and borehole measurements in the field use low-frequency, long-wavelength signals (Hz-to-kHz), while standard laboratory-measurements operate in the MHz range. This thesis advances broadband elastic wave propagation methods (quasi-static, cyclic loading, first-mode resonance, and ultrasonic) to characterize intact rocks in order to gather laboratory data relevant to field conditions. Results show the critical effect of surface roughness at the specimen-endcap interfaces on stiffness measured under quasi-static conditions; local strain measurements using specimen-bonded strain gauges avoid seating effects. Multi-mode low-frequency resonant column testing provides the most reliable assessment of attenuation; attenuation increases and resonant frequency decreases with vibration amplitude for all vibration modes (longitudinal, torsional, and flexural). Ultrasonic P and S-wave velocities increase as a function of conf fining pressure and during early stages of deviatoric loading; trends follow a Hertzian power law. The corresponding -factors and -exponents exhibit a strong correlation with specimen type. The combination of ultrasonic measurement and coda wave analysis allows us to detect minute velocity changes during fluid invasion and damage evolution. Differences in P-wave velocity in specimens saturated with brine and supercritical CO2 are higher at seismic frequencies than in ultrasonic frequencies. 5 The new experimental methods implemented in this research and the comprehensive characterization studies provide new tools into intact rock characterization and contribute new insights on the physical properties of intact rocks and fluid-matrix interaction. Results highlight critical differences between field values and standard laboratory measurements
  • High-Dimensional Analysis of Regularized Convex Optimization Problems with Application to Massive MIMO Wireless Communication Systems

    Alrashdi, Ayed (2021-03) [Dissertation]
    Advisor: Al-Naffouri, Tareq Y.
    Committee members: Alouini, Mohamed-Slim; Shihada, Basem; Kammoun, Abla; Al-Dhahir, Naofal; Davidson, Tim
    In the past couple of decades, the amount of data available has dramatically in- creased. Thus, in modern large-scale inference problems, the dimension of the signal to be estimated is comparable or even larger than the number of available observa- tions. Yet the desired properties of the signal typically lie in some low-dimensional structure, such as sparsity, low-rankness, finite alphabet, etc. Recently, non-smooth regularized convex optimization has risen as a powerful tool for the recovery of such structured signals from noisy linear measurements in an assortment of applications in signal processing, wireless communications, machine learning, computer vision, etc. With the advent of Compressed Sensing (CS), there has been a huge number of theoretical results that consider the estimation performance of non-smooth convex optimization in such a high-dimensional setting. In this thesis, we focus on precisely analyzing the high dimensional error perfor- mance of such regularized convex optimization problems under the presence of im- pairments (such as uncertainties) in the measurement matrix, which has independent Gaussian entries. The precise nature of our analysis allows performance compari- son between different types of these estimators and enables us to optimally tune the involved hyper-parameters. In particular, we study the performance of some of the most popular cases in linear inverse problems, such as the LASSO, Elastic Net, Least Squares (LS), Regularized Least Squares (RLS) and their box-constrained variants. In each context, we define appropriate performance measures, and we sharply an- alyze them in the High-Dimensional Statistical Regime. We use our results for a concrete application of designing efficient decoders for modern massive multi-input multi-output (MIMO) wireless communication systems and optimally allocate their power. The framework used for the analysis is based on Gaussian process methods, in particular, on a recently developed strong and tight version of the classical Gor- don Comparison Inequality which is called the Convex Gaussian Min-max Theorem (CGMT). We use some results from Random Matrix Theory (RMT) in our analysis as well.
  • Synthesis of novel bridged-pentanidiums and their performance in asymmetric phase-transfer catalysis

    Aresu, Emanuele (2021-03) [Dissertation]
    Advisor: Huang, Kuo-Wei
    Committee members: Rueping, Magnus; Bakr, Osman; Tan, Choon-Hong
    Abstract: Chiral phase-transfer catalysis (CPTC) is an efficient industrial process used to produce enantiomerically pure chemicals, such as agrochemicals, active pharmaceuticals ingredients (API), and monomers.1 CPTC has been applied successfully in various organic reactions with many advantages,2–6 such as mild reaction conditions, high product yields, elimination of hazardous or expensive reagents and solvents, and large- scale asymmetric productions.7 In the last decade, a chiral sp2-quaternary ammonium salt, pentanidium, reported by Tan et al. in 2011, has represented a breakthrough in this field.8 Since pentanidium catalysts have a high impact on asymmetric synthesis and are highly amenable to modification, a new class of bridged-pentanidium catalysts is discussed in this dissertation. The first part focuses on the retrosynthesis of chiral bridged-pentanidium catalysts and how they might be differently functionalized, starting the synthesis from commercial chiral diamines. As a proof-of-concept, a non-chiral bridged-pentanidium was synthesized and fully characterized. The reaction conditions were optimized for each step, particularly the critical seven-membered ring closure reaction, which proved that the retrosynthetic pathway was reliable. Next more sophisticated structures of chiral bridged-pentanidium catalysts were developed. These synthetic pathways involved the discovery of new compounds, such as chiral tertiary bisthioureas, chiral tetraamides, and chiral bisureas. Thus, various chiral bridged-pentanidium catalysts bearing various functional groups and counterions to tune their reactivity were produced. In the second part, the reactivity of chiral bridged-pentanidium catalysts was assessed in various asymmetric reactions. In particular, direct alkylation and Michael addition reactions were applied to synthesize natural and unnatural amino acids. Then, an asymmetric organocascade Michael-Michael reaction for the synthesis of chiral trisubstituted indanes was investigated. Lastly, additional control experiments involving various substrates and reagents were performed. The third part of this work investigated enantioselective induction through computational studies, including density functional theory (DFT), topographic steric maps, and topographic electrostatic maps.9 These studies characterized the properties of the previously synthesized chiral bridged-pentanidium catalysts and revealed how their enantioselectivity is affected by the structure of the catalyst. Finally, the structures and asymmetric induction of the novel chiral bridged-pentanidium catalysts were compared with those of open-pentanidium catalysts reported in the literature.
  • Nickel Complexes Incorporating the Triazine-Based PN3P Pincer and the Nonsymmetrical PONNP Pincer Ligands

    Huang, Mei-Hui (2021-03) [Dissertation]
    Advisor: Huang, Kuo-Wei
    Committee members: Mohammed, Omar F.; Tung, Vincent; Guan, Hairong
    As an extension of the previous work on the post-modification strategy of pyridine-based PN3P group 10 metal complexes, the triazine-based PN3P pincer ligands incorporating nickel complexes, Me-Et-PN3PNiCl, and Me-Et-PN3PNiI, were synthesized and characterized. The solid state structures suggest that the N-donor atom of triazine-based PN3P ligands have more electron donating than the pyridine-based PNP pincer ligands. A new non-symmetric PONNP pincer ligand system was developed to: (1) give more parameters for electronic and steric properties (2) to block the influence of acidic proton. However, the unstable metal-hydride complexes indicate the degradable O–P bond or N–P bond of the PONNP ligand. Treating the three ligands, including tert-butyl, phenyl, and cyclopentyl substituents with NiCl2(DME) individually all resulted in the production of [(PtBuONNPtBu)NiCl]+Cl-. It suggests that both O‒P and N‒P can cleave and rearrange during the complexation. The solvent effect and time tracing experiments demonstrated that the O‒P and N‒P bond rearrangement occurs after forming the nickel complex. The finding of [(ONNPtBu)NiCl]22+(Cl-)2 indicates the weakness of the O‒P bond, suggesting the degradation of an oxygen-phosphorus bond may be the initial step of substituents rearrangement. To ensure the ligand-centered reactivity of (PtBuONNPtBu)*NiCl, a nickel-silver bimetallic complex, [(PtBuONNPtBu)*NiCl]2[AgOTf]2, was produced. In contrast to pyridine-based PN3P*NiH, there are two active sites of [(PtBuONNPtBu)*NiCl]2[AgOTf]2, the N atoms on the imine arm and pyrimidine ring. The solid-structure of the acid-base adduct compound, {[(PtBuONNPtBu)*NiCl][B(C6F5)3], demonstrates that the nitrogen atom on the pyrimidine ring is a better active site than the imine arm because of the steric effect. The molecular structures of [(PtBuONNPtBu)*NiCl]2[AgOTf]2 and {[(PtBuONNPtBu)*NiCl][B(C6F5)3] exhibit that the pyrimidine ring of [(PtBuONNPtBu)*NiCl]2[AgOTf]2 tends to be an aromatic zwitterionic form. The ligand backbone of {[(PtBuONNPtBu)*NiCl][B(C6F5)3] favors the dearomatized form.
  • Monitoring Agricultural Water Use Using High-Resolution Remote Sensing Technologies

    Aragon Solorio, Bruno Jose Luis (2021-02) [Dissertation]
    Advisor: McCabe, Matthew
    Committee members: Hong, Pei-Ying; Jones, Burton; Miralles, Diego G.
    Over the coming decades, both food consumption and agricultural water use are expected to increase in response to growing populations. In light of these concerns, there has been a growing awareness and appreciation of the objectives of agricultural sustainability, which has the broad aim of securing food and water resources, without adversely affecting the environment or disenfranchising future generations. To ensure that irrigated fields optimize their water use towards a more sustainable application while remaining compliant with any imposed restrictions on access to water supplies (i.e. through water licensing), it is necessary to understand and quantify the water consumption of crops at appropriate spatial and temporal scales. Evaporation (E), also commonly referred to as evapotranspiration (ET), is the physical process of water vapor transport from the surface into the atmosphere. Evaporation can be estimated via interpretive modeling approaches that combine meteorological, radiative, vegetation, and other related properties to estimate land surface fluxes at any given time. The research presented herein aims to investigate the evaporative response of agricultural croplands across a range of spatial and temporal scales, with a focus on high-resolution and field-scale estimation. In particular, we explore the utility of novel CubeSat imagery to produce the highest spatial resolution (3 m) crop water use estimates ever retrieved from space. These high-resolution results are expanded through time by retrieving a daily evaporation product, offering an enhanced capacity to provide new insights into precision agriculture. The effects and implications of higher spatiotemporal resolutions are explored and contrasted against governmental satellite missions that operate at lower resolutions. An exploratory study on the use of unmanned aerial vehicles (UAVs) is also performed, specifically in the context of their capacity to mount miniaturized thermal sensors: with the accuracy and limitations of these sensors for deriving evaporation-type products examined. The overarching goal of this research is to advance the utility of space-based estimates of evaporation for precision agricultural applications, and to provide new high-spatial and temporal agricultural insights that can be directed towards improving water management and address food security concerns in a more sustainable manner.
  • Exploring the Reactivity of Well-defined Oxide-supported Metal­Alkyl and Alkylidyne Complexes via Surface Organometallic Chemistry

    Saidi, Aya (2021-02) [Dissertation]
    Advisor: Basset, Jean-Marie
    Committee members: Huang, Kuo-Wei; Saikaly, Pascal; Astruc, Didier
    Surface Organometallic Chemistry (SOMC) is an excellent approach to erase the gap between homogeneous and heterogeneous catalysis by grafting the molecular organometallic complex on various oxide surfaces, forming well-defined and single-site catalysts. This strategy allows for better characterization as well as the improvement and development of existing and new catalysts. These surface species could promote a wide range of catalytic applications (i.e., metathesis of hydrocarbons, hydrogenolysis of alkanes, and olefin polymerization reactions) depending on the metal center and its coordination sphere. In particular, the grafting of alkylated organometallic complexes of groups 4, 5, and 6 metals on the surface oxide is a thermodynamically favored reaction generally leading to strongly bonded well-defined surface species, which are highly reactive catalysts. This thesis has focused on the preparation, characterization, and catalytic investigation of different supported complexes that contain methyl, alkyl, and alkylidyne ligands. The first part compares the catalytic activity of [(≡Si−O−)W(-CH3)5] and [(≡Si-O-)Mo(≡CtBu)(-CH2tBu)2] surface species experimentally and by DFT calculations in the metathesis reactions of linear classical and functionalized olefins. Both pre-catalysts perform almost equally in the α-olefin metathesis reaction. However, in the functionalized olefin metathesis reaction, W pre-catalyst provides selective metathesis products and performs much better than Mo that gives a range of isomerization products. The second part deals with the synthesis and characterization of [(THF)2Zr(-CH3)4] and its grafting on silica support for the first time. The generated surface species [(≡Si−O−)Zr(CH3)3(THF)2] and [(≡Si−O−)2Zr(CH3)2(THF)2] are used for the conversion of CO2 and propylene oxide to cyclic propylene carbonates achieving a TON of 4227. The third part describes the first synthesis and characterization of the highly unstable homoleptic [Ti(-CH3)4] without any coordinating solvent. This complex was stabilized by grafting on SiO2-700, yielding two fully characterized surface species [(≡Si-O-)TiMe3] and [(≡Si-O-Si≡)(≡Si-O-)TiMe3], which were used in the hydrogenolysis reaction of propane and n-butane, with TONs of 419 and 578, respectively. Finally, the fourth part reports the immobilization and characterization of [TiMe2Cl2], an intermediate in the synthesis of [Ti(-CH3)4], on SiO2-700 resulting in [(≡Si-O-)TiMeCl2] and [(≡Si-O-)TiMe2Cl] surface species. These complexes reacted with a demethylating Lewis acid agent (BARF), forming the corresponding cationic Ti species [(≡Si-O-)TiMeCl]+ and [(≡Si-O-)TiCl2]+. Both neutral and cationic complexes were tested in the ethylene polymerization reaction affording linear HDPE with high molecular weights of 500,367 and 486,612 g/mol.
  • Autoignition and reactivity studies of renewable fuels and their blends with conventional fuels

    Issayev, Gani (2021-02) [Dissertation]
    Advisor: Farooq, Aamir
    Committee members: Sarathy, Mani; Fariborzi, Hossein; Curran, Henry J.
    Population growth and increasing standards of living have resulted in a rapid demand for energy. Our primary energy production is still dominated by fossil fuels. This extensive usage of fossil fuels has led to global warming, environmental pollution, as well as the depletion of hydrocarbon resources. The prevailing difficult situation offers not only a challenge but also an opportunity to search for alternatives to fossil fuels. Hence, there is an urgent need to explore environmentally friendly and cost-effective renewable energy sources. Oxygenates (alcohols, ethers) and ammonia are among the potential renewable alternative fuels of the future. This thesis investigates the combustion characteristics of promising alternative fuels and their blends using a combination of experimental and modelling methodologies. The studied fuels include ethanol, diethyl ether, dimethyl ether, dimethoxy methane, γ-valerolactone, cyclopentanone, and ammonia. For the results presented in this thesis, the studies may be classified into three main categories: 1. Ignition delay time measurements of ethanol and its blends by using a rapid compression machine and a shock tube. The blends studied include binary mixtures of ethanol/diethyl ether and ternary mixtures of ethanol/diethyl ether/ethyl levulinate. A chemical kinetic model has been constructed and validated over a wide range of experimental conditions. The results showed that a high-reactivity fuel, diethyl ether, may be blended with a low-reactivity fuel, ethanol, in varying concentrations to achieve the desired combustion characteristics. A ternary blend of ethanol/diethyl ether/ethyl levulinate may be formulated from a single production stream, and this blend is shown to behave similarly to a conventional gasoline. 2. Ignition delay time and flame speed measurements of ammonia blended with combustion promoters by utilizing a rapid compression machine and a constant volume spherical reactor. The extremely low reactivity of ammonia makes it unsuitable for direct use in many combustion systems. One of the potential strategies to utilize ammonia is to blend it with a combustion promoter. In this work, dimethyl ether, diethyl ether, and dimethoxy methane are explored as potential promoters of ammonia combustion. Chemical kinetic models were developed and validated in the high temperature regime by using flame speed data and in the low-to-intermediate temperature regime by using ignition delay time data. The results showed that even a small addition (~ 5 – 10%) of combustion promoters can significantly alter ammonia combustion, and diethyl ether was found to have the highest propensity to enhance ammonia ignition and flame propagation. Blends of combustion promoters with ammonia can thus be utilized in modern downsized turbo-charged engines. 3. Octane boosting and emissions minimization effects of next generation oxygenated biofuels. These studies were carried out using a cooperative fuel research engine operating in a homogenous charge compression ignition (HCCI) mode. The oxygenated fuels considered here include γ-valerolactone and cyclopentanone. The results showed that γ-valerolactone and cyclopentanone can be effective additives for octane boosting and emission reduction of conventional fuels. Overall, the results and outcomes of this thesis will be highly useful in choosing and optimizing alternative fuels for future transportation systems.
  • A versatile approach for combined algae removal and biofouling control in seawater reverse osmosis (SWRO) desalination systems

    Alshahri, Abdullah (2021-02) [Dissertation]
    Advisor: Ghaffour, NorEddine
    Committee members: Saikaly, Pascal; Pinnau, Ingo; Missimer, Thomas
    The goal of this study was to evaluate the feasibility of using advanced coagulation with Fe(VI) in coagulation-flocculation-sedimentation/ flotation systems for the pretreatment of SWRO desalination plants during algal bloom events. Algal organic matter (AOM) material extracted from marine diatom species (Chaetoceros affinis) was added to Red Sea water to mimic algal bloom conditions. Low dosage of Fe(VI) (<1 mg Fe/L) was very effective at improving feed water quality containing AOM (algal bloom conditions). Based on results from both a bench-scale DAF unit and Jar testing unit, 0.75 mg Fe/L of Fe (VI) proved to be effective at improving the raw water quality which is comparable to the performance of 1 and 3 mg Fe/L of Fe (III). The removal efficiency for both testing units with the use of Fe(VI) was up to 100% for algae , 99.99% for ATP, 99% for biopolymers and 70 % for DOC. The improvement in Fe(VI) performance is related to the simultaneous action of Fe(VI) as oxidant, disinfectant and coagulant. The performance of Fe(VI) coagulant was also evaluated with the use of coagulant aids (clays). The overall turbidity, DOC, biopolymers and algal cells removal was improved via using Fe(VI) and clays at very low dose. Generally, it was found that for the same pretreatment performance achieved, a much lower Fe(VI) dose was required compared to Fe (III), which make it important to study of cost effectiveness for using Fe(VI) instead of Fe(III) and estimate cost savings during algal bloom conditions. A detailed cost comparative study was conducted for Fe(III) vs. Fe(VI) coagulation process based on the removal efficiency. The use of Fe(VI) reduced the total pretreatment cost by 77% and sludge disposal cost by > 88% compared to the use of Fe(III) in the pretreatment process. The use of Fe(VI) reduces the operational and maintenance cost in SWRO desalination plant by 7% and the production cost by 4%. This study proved that the use of Fe(VI) during high turgidity and algal bloom conditions helped providing high raw water quality to the RO process with lower chemicals and operations cost as well as low chlorine and iron residuals.
  • A 6M Digital Twin for Reservoirs

    Zhang, Tao (2021-02) [Dissertation]
    Advisor: Sun, Shuyu
    Committee members: Stenchikov, Georgiy L.; Hoteit, Ibrahim; Yao, Jun; Yu, Bo
    Modeling and simulation of ow, transport and geo-mechanics in the subsurface porous media is an e ective approach to help make decisions associated with the management of subsurface oil and gas reservoirs, as well as in other wide application areas including groundwater contamination and carbon sequestration. Accurate modeling and e cient, robust simulation have always been the main purposes of reservoir researches, and a 6M digital twin (multi-scale, multi-domain, multi-physics and multi-numerics numerical modeling and simulation of multi-component and multiphase uid ow in porous media) is designed in this dissertation, using certain advanced models and algorithms equipped with pronounced features, to better digitally model and simulate the engineering processes and procedures in the physical reality of reservoirs and further control and optimize such processes and procedures. A comprehensive mathematical tool package is generated in the digital space, equipped with advanced models and algorithms regarding various numerical schemes including Navier-Stokes equations, LBM formulations and Darcy equation. Deep learning algorithms are incorporated in the digital space to accelerate certain time-consuming computations, for example, ash calculation and geological feature detection. A number of engineering processes are successfully re ected in the digital twin, in multiple simulation scales including in a single pore, in a porous media and in a pipeline/separator, to provide plenty of feedback to the physical entity of the industry. Finally, a complete digital twin with the 6M properties is concluded and certain promising extensions from our digital twin is organized. 5 ACKNOWLEDGEMENTS The last ve years of my student life will come to a conclusion, and I believe it is a successful one. When my dissertation is about to be completed, and when I am about to graduate, I want to express my gratitude to all the families, friends and mentors I met in the half decade. My deepest gratitude goes rst and foremost to Professor Shuyu Sun, my supervisor, who has walked me through all the stages in the learning and researches in PhD period with his careful guidance, continuing support and respectful example. Focusing on bene ting practical applications in petroleum industry, my work aims to build a bridge between the numerical methods in digital space and the engineering demand in physical world. Such a gap cannot be bridged successfully without the nurturing and leadership by an experienced and all-rounded scholar just like Prof. Sun. I would also like to acknowledge my friends and colleagues outside KAUST. Prof. Bo Yu, my main adviser in Master degree, and his team in BIPT have always been my good partners. Thanks should also go to Prof. Jianchao Cai, our closest collaborator outside KAUST. I also wish to recognize the assistance that I received from industries, including Manager Chenguang Li from CNPC and Mr. Hua Bai from PipeChina. They helped a lot in establishing the engineering scenarios for our numerical studies, and they are also my closest friends. Many thanks to Mr. Jihong Shi for your assistance and company when I was injured, and Dr. Yuze Zhang and Mr. Shuai Pang for your friendship and assistance in many ways. Finally, all my respect and love to my Mom, who has been always there supporting me with her profound belief on my abilities and relentless support to me to chase for my dreams. The world is going forward and will never stop, so as the life of us everyone's life. I wish I can always be humble and curious to touch the world and learn to live.
  • Orientation and Dimensionality Control of Two-dimensional Transition Metal Dichalcogenides

    Aljarb, Areej (2021-01-17) [Dissertation]
    Advisor: Tung, Vincent
    Committee members: Anthopoulos, Thomas D.; Han, Yu; Li, Lain-Jong; Kim, Jeehwan
    Two-dimensional (2D) transition metal dichalcogenides (TMDs) have attracted significant attention owing to their unique electrical, optical, mechanical, and thermal properties not found in their 3D counterparts. They can be obtained by mechanical, chemical, or electrochemical exfoliation. However, these strategies lack uniformity and produce defect-rich samples, making it impossible for large-scale device fabrication. Chemical vapor deposition (CVD) method emerges as the viable candidate to create atomically thin specimens at the technologically relevant scale. However, the large-scale growth of monolayer TMD films with spatial homogeneity and high electrical performance remains an unsolved challenge. The spatial inhomogeneity and the associated grain boundaries between randomly oriented domains culminate to the deleterious quality of TMDs, breaking of the long-range crystalline periodicity and introduction of insidious strain. Recent research efforts have therefore dedicated to obtaining the single crystallinity of 2D materials by controlling the orientation and dimensionality to obtain a large-scale and grain boundary-free monolayer films for Si-comparable electron mobility and overcoming the scaling limitation of traditional Si-based microelectronics,. In the first part of this thesis, orientation and dimensionality controlling of TMDs are discussed. To this end, we systematically study the growth of stereotypical molybdenum disulfide (MoS2) monolayer on a c-plane sapphire with CVD to elucidate the factors controlling their orientation. We have arrived at the conclusion that the concentration of precursors- that is, the ratio between sulfur and molybdenum oxide, plays a key role in the size and orientation of seeds, subsequently controlling the orientation of MoS2 monolayers. Later, we demonstrate a ledge-directed epitaxy (LDE) of dense arrays of continuous, self-aligned, monolayer, and single-crystalline MoS2 nanoribbons on β-gallium (iii) oxide (β-Ga2O3) (100) substrates. LDE MoS2 nanoribbons have spatial uniformity over a long-range and transport characteristics on par with those seen in exfoliated benchmarks. In the second part, we theoretically reveal and experimentally determine the origin of resonant modulation of contrast as a result of the residual 3-fold astigmatism in modern scanning transmission electron microscopy (STEM) and its unintended impact on violating the power-law dependence of contrast on coordination modes between the transition metal and chalcogenide atoms.
  • Implications of irradiance for the Red Sea Tridacna giant clam holobiont

    Rossbach, Susann (2021-01) [Dissertation]
    Advisor: Duarte, Carlos M.
    Committee members: Voolstra, Christian R.; Daffonchio, Daniele; Benzoni, Francesca; Todd, Peter A.
    Giant clams (Tridacninae subfamily) are prominent members of Indo-Pacific corals reefs, including the Red Sea, where they play multiple roles and are of distinct ecological significance for these communities. Tridacninae stand out among other bivalves as one of the few molluscan groups that live in a symbiosis with dinoflagellate Symbiodiniaceae. This relationship is comparable to the symbiosis of corals and their associated algae, where the symbionts provide a substantial amount of the respiratory carbon demand of the host through their photosynthetic activity. Their photosymbiosis restricts the distribution of the Tridacninae holobiont (i.e. giant clam host, symbiotic algae and associated bacteria) to the sunlit, shallow waters of the euphotic zone, where organisms receive sufficient incident light to maintain their high rates of primary production and calcification. However, giant clams in these shallow reefs are simultaneously exposed to potentially high and damaging levels of solar (UV) radiation. This thesis includes research on the Red Sea Tridacna spp. holobiont from an ecosystem to microscale level. It assess the abundance and distribution of Red Sea giant clams, including their associated symbiotic microalgae and bacterial microbiome. Further, it describes the strong light-dependency of calcification and primary production of Red Sea Tridacna maxima clams and reports on the effective photo-protective mechanisms that have been evolved by these clams to thrive in shallow reefs, despite levels of high solar irradiance. Tridacninae developed effective behavioral mechanisms for photo-protection, by which the clam is able to flexibly adjust its shell gaping behavior to incident light levels within a narrow time frame. On a microscale, Tridacninae use advanced photonic structures (iridocytes) within their tissues to mitigate the potential negative effects of high solar UV radiation, and to promote the photosynthesis of their symbiotic algae. Understanding the role of the Tridacna spp. holobiont for Red Sea coral reefs, its contributions to overall productivity, and its abundances in the region may serve as a baseline for further studies on this charismatic invertebrate. It may also contribute to the conservation efforts from local to regional scales, and eventually aid the protection of Tridacninae in the Red Sea and elsewhere.
  • Zaxinone, a Natural Apocarotenoid, Regulates Growth and Strigolactone Biosynthesis in Rice

    Wang, Jian You (2021-01) [Dissertation]
    Advisor: Al-Babili, Salim
    Committee members: Gojobori, Takashi; Blilou, Ikram; Bouwmeester, Harro J.
    Carotenoids are the precursor of several metabolites with regulatory functions, which include the plant hormones abscisic acid (ABA) and strigolactones (SLs), and signaling molecules, such as β-cyclocitral. These carotenoid-derivatives originate from oxidative breakdown of the double bond resulting in carbonyl cleavage-products designated as apocarotenoids. The cleavage reaction causing apocarotenoid formation is catalyzed frequently by Carotenoid Cleavage Dioxygenases (CCDs). Several lines of evidence indicate the presence of yet unidentified apocarotenoids with regulatory or signaling function. Here, we first characterized the biological functions of the apocarotenoid zaxinone formed by ZAXINONE SYNTHASE (ZAS), a member of an overlooked, widely distributed plant CCD clade. The loss-of-function rice zas mutant contains less zaxinone, exhibiting retarded growth with elevated levels of SLs that determines plant architecture, mediates mycorrhization, and facilitates the germination of root parasitic seeds, such as Striga spp. The zaxinone treatment rescued zas phenotypes, down-regulated SL biosynthesis and release, and enhanced root growth in the wild-type rice seedlings. Next, we performed multi-omics analysis demonstrating zaxinone increased sugar metabolism and induced photosynthesis in a manner that led to phenotypical changes in rice roots. Besides, transcriptome analysis showed that zaxinone upregulated CYTOKININ GLUCOSYLTRANSFERASES expression in roots, which might explain the increase in the apex and meristem length, and in the number of cellular layers. Finally, the investigation of zaxinone biology and the utilization of its application is constrained by its laborious organic synthesis and low abundance in natural sources. Therefore, we developed easy-to-synthesize and highly efficient Mimic of Zaxinone (MiZax), based on the structure-activity-relationship study using a series of apocarotenoids. Activity-based experiments unraveled MiZax3 and MiZax5 were at least as active as zaxinone in rescuing root phenotypes of the zas mutant, promoting root growth in wild-type seedlings, and reducing SL biosynthesis and release. Taken together, zaxinone is a key regulator of rice growth and development, which regulates sugar metabolism, suppresses SL biosynthesis, fine-tunes cytokinins level, and modulates biotic interactions with arbuscular mycorrhizal (AM) fungi. Our work also provides easy-to-synthesize mimics for illuminating zaxinone biology and as a tool to improve crop growth and reduce the infestation by Striga hermonthica, a severe threat to food security worldwide.
  • Sustainability Evaluation of Hybrid Desalination Systems: Multi Effect Distillation – Adsorption (MED-AD) and Forward Osmosis – Membrane Distillation (FO-MD)

    Son, Hyuk Soo (2020-12) [Dissertation]
    Advisor: Ghaffour, NorEddine
    Committee members: Vrouwenvelder, Johannes S.; Pinnau, Ingo; Orfi, Jamel
    Water is life for all living organisms on earth, and all human beings need water for every socio-economic activity in their daily lives. However, constant challenges are faced in securing quality water resources due to environmental pollution, a growing demand, and climate changes. To overcome imminent worldwide challenges on water resources, desalination of seawater and saline wastewater became inevitable, and significant efforts have been deployed by the desalination research community to advance the technology. However, there is still a gap to take it to a higher sustainability and compatibility compared to conventional water treatment technologies. Among all efforts, the hybridization of two or more processes stands among the promising solutions for sustainable desalination, which synergizes benefits of multiple technologies. To evaluate the sustainability of hybrid desalination technologies, two different systems, namely; (i) multi-effect distillation – adsorption (MED-AD) and (ii) forward osmosis – membrane distillation (FO-MD), are investigated in this study. The method developed for the analysis of primary energy consumption in complex desalination systems is used to evaluate the performance of the MED-AD pilot facility at King Abdullah University of Science and Technology (KAUST). Results of the MED-AD pilot operation showed an improvement in water production with a higher energy efficiency under the same operating conditions (near the ambient temperature with the solar thermal system). For the FO-MD hybrid system, an investigation is carried out on a novel in-house integrated module and a comparative analysis with the conventional module is provided. An isolation barrier carefully placed in the novel design enhanced the hybrid performance by reducing both concentration and temperature polarization. In addition, the FO-MD hybrid process is evaluated for brine reclamation application in a SWRO-MD-FO system. The sustainability of the proposed system and the potential of a flexible sustainable operation are presented with the experimental study with real seawater and brine from the full-scale desalination plant.
  • Shales: Comprehensive Laboratory Characterization

    Gramajo, Eduardo (2020-12) [Dissertation]
    Advisor: Santamarina, Carlos
    Committee members: Vahrenkamp, Volker C.; Mai, Paul Martin; Frost, David; Finkbeiner, Thomas
    Unconventional formations have become an increasingly important source of energy resources. Proper rock mechanic characterization is needed not only to identify the most promising areas for stimulation, but to increase our understanding of the sealing capabilities of cap-rock formations for carbon geological storage. However, shale assessment is challenging with current standard techniques. This research explores the index and rock mechanic properties of different shale specimens considered as source rocks for oil and gas (Eagle Ford, Wolfcamp, Jordanian, Mancos, Bakken, and Kimmeridge), and presents an in-depth analysis of tools and protocols to identify inherent biases. New test protocols proposed in this thesis provide robust and cost-effective measurement techniques to characterize shale formations in general; these include: 1) new energy methods computed from the area under the stress-strain curve or proposed boundary asymptotes (strength and stiffness) to assess brittle/ductile conditions in the field, 2) tensile strength analyses to determine anisotropy in shale formations, 3) Coda wave analysis to monitor pre-failure damage evolution during compression, and 4) a combination of index tests to anticipate the complicated geology or layered characteristics, which include high-resolution imaging, hardness, and scratch tests. Experimental results combined with extensive databases provide unprecedented information related to the mechanical behavior of shale formations needed for the enhanced design and analysis of geo-engineering applications. Calcareous shales display strong interlayer bonding and lower compressive strength anisotropy than siliceous shales. Tensile strength anisotropy is more pronounced than in compressive strength and reflects bedding orientation and loading conditions that affect fracture propagation and ensuing failure surface topography.
  • Exploring Entity Relationship in Pairwise Ranking: Adaptive Sampler and Beyond

    Yu, Lu (2020-12) [Dissertation]
    Advisor: Zhang, Xiangliang
    Committee members: Moshkov, Mikhail; Hoehndorf, Robert; Karypis, George
    Living in the booming age of information, we have to rely on powerful information retrieval tools to seek the unique piece of desired knowledge from such a big data world, like using personalized search engine and recommendation systems. As one of the core components, ranking model can appear in almost everywhere as long as we need a relative order of desired/relevant entities. Based on the most general and intuitive assumption that entities without user actions (e.g., clicks, purchase, comments) are of less interest than those with user actions, the objective function of pairwise ranking models is formulated by measuring the contrast between positive (with actions) and negative (without actions) entities. This contrastive relationship is the core of pairwise ranking models. The construction of these positive-negative pairs has great influence on the model inference accuracy. Especially, it is challenging to explore the entity relationships in heterogeneous information network. In this thesis, we aim at advancing the development of the methodologies and principles of mining heterogeneous information network through learning entity relations from a pairwise learning to rank optimization perspective. More specifically we first show the connections of different relation learning objectives modified from different ranking metrics including both pairwise and list-wise objectives. We prove that most of popular ranking metrics can be optimized in the same lower bound. Secondly, we propose the class-imbalance problem imposed by entity relation comparison in ranking objectives, and prove that class-imbalance problem can lead to frequency 5 clustering and gradient vanishment problems. As a response, we indicate out that developing a fast adaptive sampling method is very essential to boost the pairwise ranking model. To model the entity dynamic dependency, we propose to unify the individual-level interaction and union-level interactions, and result in a multi-order attentive ranking model to improve the preference inference from multiple views.
  • Mesoscale Eddy Dynamics and Scale in the Red Sea

    Campbell, Michael F (2020-12) [Dissertation]
    Advisor: Jones, Burton
    Committee members: Ellis, Joanne; Berumen, Michael L.; Hoteit, Ibrahim; Rainville, Luc
    Recent efforts in understanding the variability inherent in coastal and offshore waters have highlighted the need for higher resolution sampling at finer spatial and temporal resolutions. Gliders are increasingly used in these transitional waters due to their ability to provide these finer resolution data sets in areas where satellite coverage may be poor, ship-based surveys may be impractical, and important processes may occur below the surface. Since no single instrument platform provides coverage across all needed spatial and temporal scales, Ocean Observation systems are using multiple types of instrument platforms for data collection. However, this results in increasingly large volumes of data that need to be processed and analyzed and there is no current “best practice” methodology for combining these instrument platforms. In this study, high resolution glider data, High Frequency Radar (HFR), and satellite-derived data products (MERRA_2 and ARMOR3D NRT Eddy Tracking) were used to quantify: 1) dominant scales of variability of the central Red Sea, 2) determine the minimum sampling frequency required to adequately characterize the central Red Sea, 3) discriminate whether the fine scale persistency of oceanographic variables determined from the glider data are comparable to those identified using HFR and satellite-derived data products, and 4) determine additional descriptive information regarding eddy occurrence and strength in the Red Sea from 2018-2019. Both Integral Time Scale and Characteristic Length Scale analysis show that the persistence time frame from glider data for temperature, salinity, chlorophyll-α, and dissolved oxygen is 2-4 weeks and that these temporal scales match for HFR and MERRA_2 data, matching a similar description of a ”weather-band” level of temporal variability. Additionally, the description of eddy activity in the Red Sea also supports this 2-4-week time frame, with the average duration of cyclonic and anticyclonic eddies from 2018-2019 being 22 and 27 days, respectively. Adoption of scale-based methods across multiple ocean observation areas can help define “best practice” methodologies for combining glider, HFR, and satellite-derived data to better understand the naturally occurring variability and improve resource allocation.

View more