Digital Commons Network^™

Ultra-Wideband Power Amplifier Design For Large Signal Application, Ragavan Krishnamoorthy

Student Works (2020-2029)

Broadband power amplifier design has become one of the most critical enabling block in today’s wireless communication technology. Numerous research efforts have been carried out throughout the years to establish high efficiency over wideband RF transmitter. This research work presents two approaches in achieving ultra-broadband power amplifier for RF transmitter. Firstly, a new technique for the design of ultra-broadband RF power amplifier is introduced, in which a combination of the reactance compensation and third-harmonic tuning are adopted. The design goal is to achieve 40 dBm (10W) output power across a wide frequency bandwidth operation. Theoretical design equations were developed to …

Investigation On The Mechanical Properties And Microstructure Analysis Of Micro-Resistance Spot Welding Between Stainless Steel 316l And Tl-6al-4v, Mohd Mansor Muhammad Safwan

Student Works (2020-2029)

In this study, ASS 316L and Ti-6Al-4V were welded together by micro-resistance spot welding (μRSW) at different combinations of welding parameters using specifically design electrode geometry in order to acquire the optimal combination of welding parameters. The welded joint were subjected to tensile shear strength test to determine the influence of welding current, welding time, welding force and different design of elctrode tip on the mechanical properties and the strength of the welded joint. The experiment was conducted by using full factorial design of experiment (DoE) with L27 orthogonal array and utilizing the analysis of variance (ANOVA) to obtain the …

Evaluation And Inter-Comparison Of Satellite Precipitation Estimations For Extreme Flood Events In Peninsular Malaysia, Zhen Xiang Eugene Soo

Student Works (2020-2029)

Satellite precipitation products (SPP) have been useful in any hydrological applications as their extensive spatial coverage and finer space and time resolutions. However, these satellite estimations exhibit large systematic and random errors which may cause large uncertainties in any hydrological applications. In this study, three advanced satellite precipitation products, i.e. CMORPH, TRMM 3B42V7, and PERSIANN are utilized in conjunction with the ground observation to investigate their performance in detecting rain, capturing storms and rainfall pattern during extreme flood events. This study evaluates and compares the capability of the SPP by focusing on the 2014-2015 northeast monsoon extreme flood events. Three …

Effect Of Subsurface Microseismicity On The Motion Of Surrounding Dispersed Droplets -- Data, Chao Zeng, Wen Deng

Effect of Subsurface Microseismicity on the Motion of Surrounding Dispersed Droplets – Data

Spreadsheet - Data plotted in Figure 4 and Figure 5

Supporting information

Physical And Biological Factors Affecting Oxygen Transfer In The Activated Sludge Wastewater Treatment Process, Kenneth A. Campbell

Doctoral Dissertations

“The activated sludge (AS) process is widely utilized for wastewater treatment due to its versatility and general resiliency, but is energy intensive, requiring aeration and mixing energy inputs to maintain the biochemical reaction and optimize treatment performance. This study is focused on determining different factors that influence oxygen transfer and consequently its energy demand.

AS morphology, as described by the d₁₀, d₂₀, d₃₂, specific filament length (SFL), 30 min settleability (SV₃₀), etc., does influence the OTE. Filamentous organisms increase the hydrodynamic radius of suspended particles, which dilates mixed liquor apparent viscosity (µ …

Imaging In Karst Terrain Using The Electrical Resistivity Tomography (Ert) And Multi-Channel Analysis Of Surface Waves (Masw) Methods, Hassan Abdullah Alzahrani

Doctoral Dissertations

"Electrical Resistivity Tomography (ERT) and Multi-channel Analysis of Surface Waves (MASW) methods were used to image the subsurface in karst terrain in the southeast of Missouri. A SuperSting R8 system was used to acquire the ERT profiles; a multi-channel engineering seismograph was used to acquire the MASW data. The latter data were used to constrain and verify the ERT interpreted depth to top-of-rock and soil thickness. The ERT data were used to delineate the soil/rock interface and to identify zones of anomalously high moisture content within the bedrock.

The primary objective of the research was to determine the cause of …

Geophysical Assessment Of The Lake Chesterfield Site, Missouri, Diya Ali Ahmad Alfuqara

Doctoral Dissertations

"Since construction of the Lake Chesterfield, Missouri in 1986, significant leaks have occurred causing the lake to lose substantive volumes of water. Mitigation efforts, have not solved the problem. Indeed, in June of 2017, the water level in Lake Chesterfield dropped at an alarmingly rapid rate. Prior to authorizing additional mitigation work, the Lake Chesterfield. Home Owners Association (LCHOA) decided to acquire geophysical data across the drained and dry lake bed. These information would help a geotechnical engineering firm determine the most appropriate mitigation plan.

In the summer of 2018, electrical resistivity tomography, multichannel analysis of surface wave, and spontaneous-potential …

Computational Model For Neural Architecture Search, Ram Deepak Gottapu

Doctoral Dissertations

"A long-standing goal in Deep Learning (DL) research is to design efficient architectures for a given dataset that are both accurate and computationally inexpensive. At present, designing deep learning architectures for a real-world application requires both human expertise and considerable effort as they are either handcrafted by careful experimentation or modified from a handful of existing models. This method is inefficient as the process of architecture design is highly time-consuming and computationally expensive.

The research presents an approach to automate the process of deep learning architecture design through a modeling procedure. In particular, it first introduces a framework that treats …

Experimental And Modeling Studies Using Packed Bed Reactors: Liquid Phase Ethylene Production By Hydrogenation Of Acetylene, Humayun Shariff

Doctoral Dissertations

"Gas-phase catalytic hydrogenation of acetylene to produce ethylene, commonly practiced in industries, has green oil formation, which leads to catalyst deactivation and sometimes reactor runaway risks due to high exothermicity. To overcome these issues as well as to increase the selectivity and conversion, liquid-phase hydrogenation of acetylene was investigated in packed bed reactors (PBR) using a commercial catalyst. The reactor performance of two-phase flow PBRs was assessed experimentally complemented by a validated mathematical model at different scales.

The selective hydrogenation of acetylene in the liquid phase over a commercial 0.5 wt% Pd/Al₂O₃ catalyst was investigated in a …

Characterization And Recyclability Of 304l Stainless Steel Powder For Use In The Selective Laser Melting Process, Austin Taylor Sutton

Doctoral Dissertations

"Powder-bed fusion refers to a subset of additive manufacturing (AM) methods which successively melts and solidifies selected regions within a powder bed on a layer-by-layer basis to construct components directly from computer-aided design files. Laser Powder-Bed Fusion (L-PBF) is a process among the powder-bed fusion techniques that utilizes a laser to consolidate particles into a material with little porosity. During the L-PBF process, the large energy input from the laser causes the production of ejecta in the form of laser spatter and condensate, both of which have the potential to settle in the surrounding powder bed compromising its reusability. In …

Experimental Investigation Of Ionic Liquid Mixtures For Electrospray Propulsion, Mitchell J. Wainwright

Doctoral Dissertations

"In recent years, there has been a dramatic increase in the number of small satellites (namely MicroSats, NanoSats, and CubeSats) in earth orbit; many of these are launched without propulsion systems. Multi-mode propulsion systems, capable of operating in either chemical or electric mode, have been proposed as attractive candidates for use in small satellites. Such systems are mass and volume optimal and flexible in terms of thrust requirements. Most previous work on multi-mode systems has focused on chemical mode performance.The work in this dissertation focuses on the electric mode performance of these propulsion systems.

The work in this research is …

Novel Approaches For Reliable And Efficient Circuit Design, Prashanthi Metku

Doctoral Dissertations

"In this research work, a suite of approaches are presented to improve reliability of 3D heterogeneous processors (3DHP) and to reduce the area overhead of asynchronous designs. This work is primarily divided into two parts. In the first part, we present an approach for improving reliability in 3DHP. Typically, in 3DHP, thermal hotspots introduce spatial and temporal variability that results in wide bit error variation in DRAM dies. To address this issue multi- path BCH decoder is introduced. Based on the thermal gradient data generated by on-chip temperature sensors, the proposed methodology specializes in adaptively estimating the number of errors …

Microgrid Design, Control, And Performance Evaluation For Sustainable Energy Management In Manufacturing, Md. Monirul Islam

Doctoral Dissertations

"This research studies the capacity sizing, control strategies, and performance evaluation of the microgrids with hybrid renewable sources for manufacturing end use customers towards a distributed sustainable energy system paradigm. Microgrid technology has been widely investigated and applied in commercial and residential sector, while for manufacturers, it has been less explored and utilized. To fill the gap, the dissertation first proposes a cost-effective sizing model to identify the capacities as well as control strategies of the components in microgrids considering a commonly used energy tariff, i.e., Time of Use (TOU). Then, the sizing model is extended by integrating control strategies …

Towards Efficacy And Efficiency In Sparse Delay Tolerant Networks, Douglas John Mcgeehan

Doctoral Dissertations

"The ubiquitous adoption of portable smart devices has enabled a new way of communication via Delay Tolerant Networks (DTNs), whereby messages are routed by the personal devices carried by ever-moving people. Although a DTN is a type of Mobile Ad Hoc Network (MANET), traditional MANET solutions are ill-equipped to accommodate message delivery in DTNs due to the dynamic and unpredictable nature of people's movements and their spatio-temporal sparsity. More so, such DTNs are susceptible to catastrophic congestion and are inherently chaotic and arduous. This manuscript proposes approaches to handle message delivery in notably sparse DTNs. First, the ChitChat system [69] …

Strengthening Qc Relaxations Of Optimal Power Flow Problems By Exploiting Various Coordinate Changes, Mohammad Rasoul Narimani

Doctoral Dissertations

"Motivated by the potential for improvements in electric power system economics, this dissertation studies the AC optimal power flow (AC OPF) problem. An AC OPF problem optimizes a specified objective function subject to constraints imposed by both the non-linear power flow equations and engineering limits. The difficulty of an AC OPF problem is strongly connected to its feasible space's characteristics. This dissertation first investigates causes of nonconvexities in AC OPF problems. Understanding typical causes of nonconvexities is helpful for improving AC OPF solution methodologies.

This dissertation next focuses on solution methods for AC OPF problems that are based on convex …

Evaluation Of The Performance Of Different Polymer Gel Systems As An In-Depth Gel Treatment Using Numerical Simulation, Tariq K. Khamees

Doctoral Dissertations

"Oil production from heterogeneous and naturally fractured reservoirs are usually hindered due to the presence of high-permeability streaks and natural fractures networks. Oil production could be more lowered if there is a crossflow from the high- to the low-permeability layers and high mobility ratio. These problems are called conformance problems and the treatment is called conformance improvement technologies (CITs). The aims of CIT is to correct the heterogeneity of the reservoir and to lower the unfavorable mobility ratio. These technologies are leading to the diversion of post-treatment water into the low-permeability layers and to increase the viscosity of the displacing …

Seismological Investigations Of Lithospheric Structure Beneath The East African Rift System And The Kalahari Craton, Tuo Wang

Doctoral Dissertations

"In spite of numerous geophysical studies have been conducted in East African Rift System and Southern Africa, the structure and evolution of the crust and upper mantle are still controversial. In this study, we applied multiple seismological techniques to investigate the structure in the crust and uppermost mantle beneath the East African Rift System and Kalahari Craton in southern Africa. First, the technique of ambient noise tomography was applied to image shear wave velocity model from surface to the depth of 40 km beneath the Malawi and Luangwa rift zones. For the first time, a high-resolution 3-D shear wave velocity …

Observer-Based Event-Triggered And Set-Theoretic Neuro-Adaptive Controls For Constrained Uncertain Systems, Abdul Ghafoor

Doctoral Dissertations

"In this study, several new observer-based event-triggered and set-theoretic control schemes are presented to advance the state of the art in neuro-adaptive controls. In the first part, six new event-triggered neuro-adaptive control (ETNAC) schemes are presented for uncertain linear systems. These comprehensive designs offer flexibility to choose a design depending upon system performance requirements. Stability proofs for each scheme are presented and their performance is analyzed using benchmark examples. In the second part, the scope of the ETNAC is extended to uncertain nonlinear systems. It is applied to a case of precision formation flight of the microsatellites at the Sun-Earth/Moon …

System Si/Pi Modeling And Analysis, Biyao Zhao

Doctoral Dissertations

"A physics-based circuit modeling methodology for 3D IC/packages is proposed here. The method is based on partial element equivalent circuit (PEEC) and layered Green's function (LGF). The LGFs are calculated from discrete complex image method (DCIM) with three terms, direct coupling, complex images, and surface wave, extracted to analyze the wave behavior. The dominate terms for LGFs are analyzed for four stack-ups in 3D IC/packages. Analytical formulas that include the contribution of complex images are proposed for partial capacitance calculation, with the complex image extracted from LGFs. A chip PDN geometry is used to illustrate the use of LGF in …

Minimizing The Detrimental Effects Of Hydro-Peaking On Riverbank Instability: The Lower Osage River Case, Wesam Sameer Mohammed-Ali

Doctoral Dissertations

"The fluctuation of water level downstream from dams due to hydropower flow releases negatively affects the riverbank stability. Therefore, this research aims to examine the feasibility of using an optimization technique to mitigate the riverbank instability resulting from the outflow variation of hydropower plants. The effects of the water releases from the Bagnell Dam were investigated by computing a series of safety factors for 78 cross sections along the 81-mile stretch of the lower Osage River in relation to outflow events by using the integrated BSTEM model incorporated into the HEC-RAS model. The 1-D sediment transport and unsteady flow in …

Frequency Selective Surface-Based Sensing: Theory And Applications, Mahboobeh Mahmoodi

Doctoral Dissertations

"Frequency selective surfaces (FSS) are periodic arrays of resonant elements with a specific (resonant) reflection/transmission response when illuminated by electromagnetic energy. FSSs have been utilized for different applications such as spatial filters, reflectors, lenses, radomes, and more recently, as sensors. FSS-based sensors have shown potential for numerous applications in structural health monitoring such as crack detection, concurrent strain and temperature sensing, normal and shear strain sensing, inspection of layered structures, etc. As FSS-based sensing is largely undeveloped, there are many critical aspects that must be fully understood before this sensing approach can be fully utilized. Therefore, the goal of this …

Polymeric Nanoparticle As A New Platform For High Removal Of Endotoxins From Biopharmaceutical Solutions, Sidharth Razdan

Doctoral Dissertations

"Presently, approximately one-third of all biopharmaceutical drugs are derived from biological sources like gram-negative bacteria. Gram-negative bacteria like E.coli are much cheaper to cultivate and provide higher biotherapeutic yield compared to mammalian cells. On extracting the useful biotherapeutics from the gram-negative bacterial cells (E.coli), endotoxin present in the bacteria is released in the surrounding media thus contaminating the lifesaving biotherapeutics. Application of the endotoxin-contaminated therapeutics to humans or animals can cause serious health issues like septic shock, tissue injury and ultimately death. Hence, thorough purification of biotherapeutics before parenteral application is necessary. Although there are multiple methods for …

Experimental Study On A Novel Eor Method -- Polymeric Nanogel Combined With Surfactant And Low Salinity Water Flooding To Enhance Oil Recovery, Mustafa M. Almahfood

Doctoral Dissertations

“Extracting higher amounts of oil from current reservoirs is a necessity for the oil industry to enhance their profitability and sustainability. The desire to recover more oil from the existing reservoirs has led to a growing interest of nanoparticle application in enhanced oil recovery (EOR). However, most researchers have focused on the evaluation and surface modification of non-deformable nanoparticles. This dissertation evaluates the potential of deformable nanogel particles as an EOR material when they are combined with two other promising technologies - surfactant and low salinity water floodings. The particle size distribution, ζ-potential and interfacial tension were measured for a …

Characterization Of Neutron Irradiated Accident Tolerant Nuclear Fuel Cladding Silicon Carbide & Radiation Detector Deadtime, Bader Almutairi

Doctoral Dissertations

“In part I, the pulse shape characteristics generated by a Geiger Muller (GM) detector and recorded by an oscilloscope manually, were investigated. The objective of part I was (1) to find a correlation between pulse shape and the operating voltage; and (2) to assess if pulse shape properties followed distinct patterns comparable to detector deadtime findings reported by a previous study. It was observed that (1) there is a strong correlation between pulse shape and operating voltage, and (2) pulse shape falls in three distinct regions similar to detector deadtime. Furthermore, parts II and III are companions and share the …

Mesh Networking And Full-Duplex Communication For Wireless Networks, Arul Mathi Maran Chandran

Doctoral Dissertations

“Connectivity with large coverage area; and an increase in spectral efficiency of communications are highly desired features for any wireless network. The presented research work addresses these two feature improvements. First, the work analyzed mesh networks to enhance connectivity for wireless networks. The work analyzed both homogeneous and heterogeneous mesh networks. The work includes the development of an Android application to enable smartphones with multiple interfaces, such as Wi-Fi, Bluetooth, and cellular services, to become convergence devices. These convergence devices are then used to build a heterogeneous mesh network improving connectivity and coverage area. Second, the work explored full-duplex communications, …

Understanding The Deformation Mechanisms In Ni-Based Superalloys With Using Crystal Plasticity Finite Element Method, Tianju Chen

Doctoral Dissertations

“Ni-based superalloy is considered as a good candidate due to its excellent resistance to elevated temperature deformation for long term period application. Understanding the deformation and failure mechanisms of Ni-Based superalloys is very helpful for providing design guidelines for processing Ni-based superalloys. Experimental characterization indicates that the deformation mechanisms of Ni based superalloy is strongly microstructure dependent. Besides, damage transform from the void nucleation to the macro cracks by voids growth leading to the failure of the Ni-based superalloys are also showing strong microstructure sensitivity. Therefore, this work focuses on the prediction and comprehension of the deformation and void growth …

Effect Of Turbulence Model Closure Coefficient Uncertainty On Scramjet Flow Field Analysis, Martin Albert Di Stefano

Doctoral Dissertations

“The numerical modeling of supersonic combustion ramjet (scramjet) engine flow paths plays an important role in the design of hypersonic air-breathing propulsion systems. Due to the complexity of the flow field physics and limited experimental data, numerical models possess uncertainties which should be addressed to improve the prediction accuracy of the simulations. In this study, the effect of turbulence model closure coefficient uncertainty on the Reynolds-averaged Navier-Stokes solution of a scramjet isolator and scramjet strut fuel injector flow field is investigated with an uncertainty quantification and sensitivity analysis study for commonly used turbulence models. Turbulence models considered in this work …

Combustion And Emission Characteristics Of Ic Engines Fueled By Hydrogen And Hydrogen/Diesel Mixtures And Multi-Objective Optimization Of Operating Parameters, Abdulhakim Issa Jabbr

Doctoral Dissertations

“The present study considers combustion of hydrogen in IC engines. In general, the work focuses on simulating the engine performance and emissions at different operation parameters, and using optimization techniques. Task I work deals with the engine performance and emissions of a single cylinder spark-ignition (SI) engine fueled by hydrogen. The engine was simulated at different equivalence ratios, exhaust gas recirculation (EGR) and ignition timing. The results indicate that NOx emissions, engine power, and efficiency are reduced by increasing EGR level, and increased with increasing equivalence ratio and advanced ignition timing. The best operating conditions for hydrogen engines were obtained …

Studies On The Stability Of Plasma Proteins And Their Fragments, Paul Praveen Nakka

Doctoral Dissertations

“The stability of a protein-based biological drug is an important concern during processing, storage or patient administration. There are various forces which contribute to the stabilizing of proteins. Both hydrogen bonds and hydrophobic interactions play an important role in protein stability. Improper folding or misfolding of proteins leads to aggregation, which is a major problem found in the bioprocessing industry. The objectives of this research are: 1) to determine the effect of environmental factors such as pH, temperature, additives or salts, and cosolvents on the stability human serum albumin (HAS), which is the most abundant protein in plasma, 2) to …

Generalization Of Polynomial Chaos For Estimation Of Angular Random Variables, Christine Louise Schmid

Doctoral Dissertations

“The state of a dynamical system will rarely be known perfectly, requiring the variable elements in the state to become random variables. More accurate estimation of the uncertainty in the random variable results in a better understanding of how the random variable will behave at future points in time. Many methods exist for representing a random variable within a system including a polynomial chaos expansion (PCE), which expresses a random variable as a linear combination of basis polynomials.

Polynomial chaos expansions have been studied at length for the joint estimation of states that are purely translational (i.e. described in Cartesian …