Digital Commons Network^™

A Novel Relaxed Hierarchical Equivalent Source Algorithm (Rhesa) For Electromagnetic Scattering Analysis Of Dielectric Objects, Xin Fu, Li (Lijun) Jun Jiang, Hong Tat Ewe

Electrical and Computer Engineering Faculty Research & Creative Works

A novel relaxed hierarchical algorithm based on the surface equivalence principle for the volume integral equations (VIEs) is proposed in this work. The equivalent sources residing on relaxed spherical equivalence surfaces are established by exact integral formulations. The equivalence surfaces are exploited hierarchically to accelerate matrix–vector product in iterative solutions for the VIEs. The computation time and memory cost complexity of the proposed algorithm for dielectric scatters scale as O(N4/3) and O(N) , respectively. Numerical examples validate the accuracy and capability of the proposed algorithm.

Properties Of Self-Compacting Concrete With Recycled Coarse Aggregate, W. C. Tang, P. C. Ryan, H. Z. Cui, W. Liao

Civil, Architectural and Environmental Engineering Faculty Research & Creative Works

The utilization of recycled concrete aggregate (RCA) in Self-Compacting Concrete (SCC) has the potential to reduce both the environmental impact and financial cost associated with this increasingly popular concrete type. However, to date limited research exists exploring the use of coarse RCA in SCC. The work presented in this paper seeks to build on the existing knowledge in this area by examining the workability, strength, and fracture properties of SCCs containing 0%, 25%, 50%, 75%, and 100% coarse RCA. The experimental programme indicated that at RCA utilization levels of 25% to 50% little or no negative impact was observed for …

Geometric Consideration Of Nanostructures For Energy Storage Systems, Jonghyun Park, Jie Li, Wei Lu, Ann Marie Sastry

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Battery performance and its fade are determined by various aspects such as the transport of ions and electrons through heterogeneous internal structures; kinetic reactions at the interfaces; and the corresponding interplay between mechanical, chemical, and thermal responses. The fundamental factor determining this complex multiscale and multiphysical nature of a battery is the geometry of active materials. In this work, we systematically consider the tradeoffs among a selection of limiting geometries of media designed to store ions or other species via a diffusion process. Specifically, we begin the investigation by considering diffusion in spheres, rods, and plates at the particle level, …

Mitigation Emission Strategy Based On Resonances From A Power Inverter System In Electric Vehicles, L. Zhai, Xinyu Zhang, Natalia G. Bondarenko, David Loken, Thomas Van Doren, Daryl G. Beetner

Electrical and Computer Engineering Faculty Research & Creative Works

Large dv/dt and di/dt outputs of power devices in the DC-fed motor power inverter can generate conducted and/or radiated emissions through parasitics that interfere with low voltage electric systems in electric vehicles (EVs) and nearby vehicles. The electromagnetic interference (EMI) filters, ferrite chokes, and shielding added in the product process based on the "black box" approach can reduce the emission levels in a specific frequency range. However, these countermeasures may also introduce an unexpected increase in EMI noises in other frequency ranges due to added capacitances and inductances in filters resonating with elements of the power inverter, and even increase …

Coupled Crystal Orientation-Size Effects On The Strength Of Nano Crystals, Rui Yuan, Irene J. Beyerlein, Caizhi Zhou

Materials Science and Engineering Faculty Research & Creative Works

We study the combined effects of grain size and texture on the strength of nanocrystalline copper (Cu) and nickel (Ni) using a crystal-plasticity based mechanics model. Within the model, slip occurs in discrete slip events exclusively by individual dislocations emitted statistically from the grain boundaries. We show that a Hall-Petch relationship emerges in both initially texture and non-textured materials and our values are in agreement with experimental measurements from numerous studies. We find that the Hall-Petch slope increases with texture strength, indicating that preferred orientations intensify the enhancements in strength that accompany grain size reductions. These findings reveal that texture …

Refractive Index And Thermo-Optic Coefficients Of Ge-As-Se Chalcogenide Glasses, Benn Gleason, Kathleen Richardson, Laura Sisken, Charmayne Smith (Lonergan)

Materials Science and Engineering Faculty Research & Creative Works

Seventeen glasses in the Ge-As-Se ternary glass-forming region have been fabricated and analyzed to provide input for optical design data and to establish composition- and structure-based relationships to aide development of novel chalcogenide glasses with tailored optical functionality. While known that Ge addition to binary As-Se glasses enhances the mean coordination number (MCN) of the network and results in increased Tg and decreased CTE, this work highlights the impact on optical properties, specifically mid-wave (λ = 4.515 μm) index and thermo-optic coefficient (dn/dT). Trends in property changes were correlated with an excess or deficiency of chalcogen content in the glassy …

Effect Of Powder Particle Size On The Fabrication Of Ti-6al-4v Using Laser Metal Deposition From Elemental Powder Mixture, Xueyang Chen, Lei Yan, Wei Li, Frank W. Liou, Joseph William Newkirk

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Direct LMD (laser metal deposition) was used to fabricate thin-wall Ti-6Al-4V using the powder mixture of Ti-6 wt.%Al-4 wt.%V. SEM (scanning electron microscopy), OM (optical microscopy) and EDS (energy dispersive spectroscopy) were employed to examine the chemical composition and microstructure of the as-deposited sections. Vickers hardness tests were then applied to characterize the mechanical properties of the deposit samples which were fabricated using pre-mixed elemental powders. The EDS line scans indicated that the chemical composition of the samples was homogenous across the deposit. After significant analysis, some differences were observed among two sets of deposit samples which varied in the …

Structure And Corrosion Behavior Of Sputter Deposited Ce-Al-O Coating On Al 2024-T3 Alloy Substrates, Yuanyuan Liu, Jiamu Huang, James B. Claypool, Matthew J. O'Keefe

Materials Science and Engineering Faculty Research & Creative Works

Deposition of Ce-Al-O coatings on Al 2024-T3 alloy substrates was conducted by magnetron co-sputtering of CeO₂ and Al targets. The incorporation of Al into the CeO₂ film resulted in an amorphous or nanocrystalline structure with binding energy states different from Al, Al₂O₃, and CeO₂. Electrochemical measurements indicated that the amorphous or nanocrystalline Ce-Al-O coating increased the corrosion resistance of bare Al 2024-T3 substrates by more than three orders of magnitude and exhibited a very different cathodic and anodic protective mechanism compared to Al and CeO₂ coated and as-polished Al 2024-T3 samples. …

Behavior Of Hollow-Core Composite Columns Under Torsion Loading, Sujith Anumolu

Masters Theses

"The effect of torsional loads could be significant along with axial and flexural loads on bridge columns during earthquake excitations. The present study presents the torsional behavior of hollow-core steel-concrete-steel columns (HC-SCS) and hollow-core fiber reinforced polymer-concrete-steel columns (HC-FCS). The HC-SCS comprises of sandwiched concrete shell between two steel tubes whereas in HC-FCS column, the outer steel tube of HC-SCS column was replaced by the FRP tube. Both columns have stay-in place permanent form-work to the concrete shell in the form of outer and inner tubes. The steel tubes serve as longitudinal and shear reinforcement to the column. Finite element …

Using Adaptive Thresholding And Skewness Correction To Detect Gray Areas In Melanoma In Situ Images, Jason R. Hagerty

Masters Theses

"The incidence of melanoma in situ (MIS) is growing significantly. Detection at the MIS stage provides the highest cure rate for melanoma, but reliable detection of MIS with dermoscopy alone is not yet possible. Adjunct dermoscopic instrumentation using digital image analysis may allow more accurate detection of MIS. Gray areas are a critical component of MIS diagnosis, but automatic detection of these areas remains difficult because similar gray areas are also found in benign lesions. This paper proposes a novel adaptive thresholding technique for automatically detecting gray areas specific to MIS. The proposed model uses only MIS dermoscopic images to …

Effect Of Build Parameters On Mechanical Properties Of Ultem 9085 Parts By Fused Deposition Modeling, Krishna Prasanth Motaparti

Masters Theses

"Additive manufacturing is a fabrication technique that is used to build components by depositing material in a layer-by-layer manner. Fused Deposition Modeling (FDM) is one of the additive manufacturing techniques which is widely used for prototyping and production applications of thermoplastic components. In load bearing applications, the flexural and compression forces often coexist. In order to avoid failure under these loads, it is essential to study the mechanical properties of the components fabricated by FDM. The main focus of this research is to study the mechanical properties of the fabricated components and to comprehend their dependence on various build parameters. …

Variable Stress Orientations In The Offshore Nile Delta: The Role Of Salt As A Mechanical Detachment Horizon, Weicheng Zhang

Masters Theses

"The offshore Nile Delta is characterized by variations of the maximum horizontal stress orientation in subsalt and supra-salt sequences. Margin-parallel SH, typical for tertiary deltas, is observed for regions that are below or do not contain evaporites. In sequences underlain by evaporates pre-dominantly margin-normal SH is observed. This observation yielded the first conclusive in situ evidence that salt acts as a mechanical detachment layer. In this study, 3D finite element analysis (FEA) is used to simulate the total stress distribution in the offshore Nile Delta featuring evaporate sequences. Several parameters such as different salt sequence geometries, friction coefficient on faults, …

A Study On Non-Metallic Inclusions In Foundry Steel Process, Marc Leonard Harris

Masters Theses

"The effects of sample area and automated SEM/EDS feature analysis parameters (step size, magnification and threshold) on nonmetallic inclusion characterization results has been investigated and optimized. A post-processing program was developed to automatically determine average inclusion chemistry, total element concentrations within inclusions, and for generating joint ternary diagrams with size visualization for representing nonmetallic inclusion populations. Using these tools the evolution of nonmetallic inclusions was examined for 4320 steel at a participating industrial steel foundry. The steel was sampled throughout electric arc furnace melting through ladle refining to the final casting where an in-mold sampling procedure was developed to procure …

Intensity Control Of Dielectric Barrier Discharge Filaments, Matthew Crawford Paliwoda

Masters Theses

"When operated in a filamentary mode, a volume dielectric barrier discharge (DBD) is known to produce patterned plasma structures. These structures are currently being explored for reconfigurable metamaterial applications. In this work the presence and intensity of a single filament, within an array of filaments, was controlled by adjusting the voltage to that filament's individual needle electrode. The current, voltage, and time-averaged normalized light intensity were measured while varying the voltage of the needle through a self-biasing resistance. For a 7.5 kV, 3.2 kHz DBD in air, the needle-controlled filament intensity varies from that of the surrounding filaments to zero …

De-Embedding Method For Electrical Response Extraction Of Through-Silicon Via (Tsv) In Silicon Interposer Technology And Signal Integrity Performance Comparison With Embedded Multi-Die Interconnect Bridge (Emib) Technology, Qian Wang

Masters Theses

"Traditional two-dimensional system-in-package (2D SiP) can no longer support the scaling of size, power, bandwidth, and cost at the same rate required by Moore's Law. Three-dimensional integrated circuits (3D-ICs), 2.5D silicon interposer technology in which through silicon vias are widely used, are implemented to meet these challenges. Embedded multi-die interconnect bridge (EMIB) technology are proposed as well.

In Section 1, a novel de-embedding method is proposed for TSV characterization by using a set of simple yet efficient test patterns. Full wave models and corresponding equivalent circuits are provided to explain the electrical performance of the test patterns clearly. Furthermore, broadband …

A Statistical Analysis Of A 4.5 Mw Solar Energy Center, Archit Patnaik

Masters Theses

"This project helps a regional utility evaluate the performance of their 4.5 MW photovoltaic plant. The performance evaluation consists of characterizing the peak and average power and energy output of the plant over varying time periods. A characterization of the output power drops, or dips, is done by performing a statistical analysis of the photovoltaic plant output data. Dips are characterized by dip frequency, depth of dip, energy loss by dip, and dip duration. The results of this study will help the utility to select appropriate voltage regulating equipment on the basis of dip characteristics, and thus, optimize the performance …

Sub-Millisecond Response Time In A Photorefractive Composite Operating Under Cw Conditions, Jong-Sik Moon, Tyler E. Stevens, Todd C. Monson, Dale L. Huber, Sung-Ho Jin, Jin-Woo Oh, Jeffrey G. Winiarz

Chemistry Faculty Research & Creative Works

Extensive study of photorefractive polymeric composites photosensitized with semiconductor nanocrystals has yielded data indicating that the inclusion of such nanocrystals enhances the charge-carrier mobility, and subsequently leads to a reduction in the photorefractive response time. Unfortunately, the included nanocrystals may also act as a source of deep traps, resulting in diminished diffraction efficiencies as well as reduced two beam coupling gain coefficients. Nonetheless, previous studies indicate that this problem is mitigated through the inclusion of semiconductor nanocrystals possessing a relatively narrow band-gap. Here, we fully exploit this property by doping PbS nanocrystals into a newly formulated photorefractive composite based on …

The Virtual Atomic And Molecular Data Centre (Vamdc) Consortium, Marie-Lise Dubernet, B. K. Antony, Ernesto Quintas-Sánchez, For Full List Of Authors, See Publisher's Website.

Chemistry Faculty Research & Creative Works

The Virtual Atomic and Molecular Data Centre (VAMDC) Consortium is a worldwide consortium which federates atomic and molecular databases through an e-science infrastructure and an organisation to support this activity. About 90% of the inter-connected databases handle data that are used for the interpretation of astronomical spectra and for modelling in many fields of astrophysics. Recently the VAMDC Consortium has connected databases from the radiation damage and the plasma communities, as well as promoting the publication of data from Indian institutes. This paper describes how the VAMDC Consortium is organised for the optimal distribution of atomic and molecular data for …

Post-Disaster Supply Chain Interdependent Critical Infrastructure System Restoration: A Review Of Data Necessary And Available For Modeling, Varun Ramachandran, Suzanna Long, Tom Shoberg, Steven Corns, Hector J. Carlo

Engineering Management and Systems Engineering Faculty Research & Creative Works

The majority of restoration strategies in the wake of large-scale disasters have focused on short-term emergency response solutions. Few consider medium- to long-term restoration strategies to reconnect urban areas to national supply chain interdependent critical infrastructure systems (SCICI). These SCICI promote the effective flow of goods, services, and information vital to the economic vitality of an urban environment. To re-establish the connectivity that has been broken during a disaster between the different SCICI, relationships between these systems must be identified, formulated, and added to a common framework to form a system-level restoration plan. To accomplish this goal, a considerable collection …

Adaptive Filters For Sparse System Identification, Jianming Liu

Doctoral Dissertations

"Sparse system identification has attracted much attention in the field of adaptive algorithms, and the adaptive filters for sparse system identification are studied. Firstly, a new family of proportionate normalized least mean square (PNLMS) adaptive algorithms that improve the performance of identifying block-sparse systems is proposed. The main proposed algorithm, called block-sparse PNLMS (BS-PNLMS), is based on the optimization of a mixed ℓ_2,1 norm of the adaptive filter's coefficients. A block-sparse improved PNLMS (BS-IPNLMS) is also derived for both sparse and dispersive impulse responses. Meanwhile, the proposed block-sparse proportionate idea has been extended to both the proportionate affine projection …

Geophysical Imaging Of Karst Features In Missouri, Jeremiah Chukwunonso Obi

Doctoral Dissertations

"Automated electrical resistivity tomography (ERT) supported with multichannel analysis of surface waves (MASW) and boring data were used to map karst related features in Missouri in order to understand karst processes better in Missouri. Previous works on karst in Missouri were mostly surficial mapping of bedrock outcrops and joints, which are not enough to define the internal structure of karst system, since most critical processes in karst occur underground. To understand these processes better, the density, placement and pattern of karst related features like solution-widened joints and voids, as well as top of bedrock were mapped. In the course of …

Subterranean Photobioreactors For Commercial-Industrial Scale Algal Culture, Daniel James Vidt

Doctoral Dissertations

"There are many potential benefits to the mining industry accruing from the application of algal biotechnology. The main benefits are in the production of biodiesel and in the remediation of mining brownfields. The research in this study was centered in the original idea that these brownfields represent a tremendous opportunity for use as a hybrid model for redevelopment into sustainable "mines" of biomass. The ability of these underground spaces serving as bioreactors to control all aspects of the growing environment, from lighting, to temperature, to biosecurity, are key advantages that have been identified in the literature. The many benefits inherent …

Proactive Strategies In Personal Dose Monitoring, Prevention And Mitigation, Manish Kumar Sharma

Doctoral Dissertations

"At certain threshold, nuclear radiation (like x-rays and gamma-rays) may adversely impact the health of living tissues. The exposure to these radiations in nuclear facilities is measured by devices called dosimeters. The devices are generally worn on the torso and are monitored by health physics division to report the radiation dose received by the personnel. However, this approach is not proactive--since the dosimeters reflect the dose that has already been absorbed in the body of the wearer.

This work presents a scheme to proactively avoid large dose acquisition at radiation-prone facilities. The work was divided into three major segments: (i) …

Composite Confinement Systems For Rc Column Repair And Construction Under Seismic Loads: Concept, Characterization And Performance, Mostafa Fakharifar

Doctoral Dissertations

"This study aims at developing, characterizing and validating an integrated composite confinement system of conventional jackets for: (1) repair and retrofit of existing bridge columns; and (2) construction of new bridge columns, subjected to earthquake excitations.

A new composite steel confinement jacket was proposed by combining a thin steel sheet and prestressing strands as a hybrid jacket, incorporating active and passive confining pressure on damaged RC columns. Both experimental and analytical studies were conducted to understand the performance and effectiveness of the proposed repair method. The experimental study involved two 1/2-scale lap-spliced deficient RC bridge columns originally tested to failure …

Phase Field Modeling Of Electrodeposition Process In Lithium Metal Batteries, Nihal Acharya

Masters Theses

"One of the main weaknesses in long term performance of conventional lithium batteries is the growth of lithium microstructures on the electrode surface due to an electrochemical process, which can eventually lead to failure of these batteries. Suppressing this microstructure growth is a key in developing new generations of lithium metal batteries (LMBs). In this study, a two-dimensional (2D) phase field model is constructed to understand and determine the parameters controlling formation and evolution of microstructures in LMBs. A Ginzburg-Landau free energy functional, which is a function of concentration of Li⁺ and applied voltage, and a system consisting of …

Mechanics Of Impulse Force Reduction For Mitigating Dump Truck Vibrations Under Hislo Conditions, Danish Ali

Masters Theses

"The deployment of large capacity shovels and dump trucks, for achieving economic bulk production capacities, has resulted in high impact shovel loading operations (HISLO). These large shovels generate high impact forces when loading dump trucks with over 100-ton passes under gravity. The impact forces also generate high frequency shock waves, which cause severe truck vibrations, and thus, expose dump truck operators to high levels of whole body vibrations (WBV). The dynamic impact force generates these vibrations, and thus, there is a need to develop efficient technologies to eliminate or reduce its impact. Existing literature and industry practice show that this …

Effect Of Cooperation On Players' Immersion And Enjoyment, Lakshmi Sushma Daggubati

Masters Theses

"This research examines the effect of cooperative versus non-cooperative game play on immersion and enjoyment in online games. It draws on the self-determination theory to generate the research hypotheses and explain the observed phenomenon. A within-subject experimental design (N=38) was used to evaluate the effects of cooperative versus non-cooperative game play on enjoyment and immersion by having participants play in a manipulated game mode in a controlled gaming environment. The participants' subjective responses were assessed to understand their user experience in cooperative and non-cooperative gaming environments. The results suggest that both immersion and enjoyment were significantly enhanced in cooperative game …

Tracking Silver, Gold, And Titanium Dioxide Nanoparticles Through Drinking Water Systems By Single Particle - Inductively Coupled Plasma - Mass Spectrometry, Ariel Renee Donovan

Masters Theses

"Single particle (SP)-ICP-MS methods were developed to characterize and quantify Ti-containing, titanium dioxide, silver, and gold NP concentration, size, size distribution and dissolved metal element concentration in surface water and treated drinking water. The effectiveness of conventional drinking water treatments (including lime softening, alum coagulation, filtration, and disinfection) to remove NPs from surface water was evaluated using six-gang stirrer jar test simulations. Six-gang stirrers were used to simulate drinking water treatments including lime softening, alum coagulation, powdered activated carbon sorption, filtration, and disinfection by free chlorine. Lime softening effectively removed most nanoparticles added. Source and drinking waters from three large …

The Mantle Transition Zone Beneath South America From Stacking Of P-To-S Receiver Functions, B. A. Goetze

Masters Theses

"The Mantle Transition Zone (MTZ) beneath South America is investigated with stacking of Receiver Functions (RFs) of converted P-to-S phases from the velocity discontinuities at 410 km (d410) and 660 km (d660). A total of 785 seismic stations provided 22,235 high quality RFs, allowing 1,717 MTZ thickness measurements in circular bins of 2⁰ radius. An apparent MTZ structure is derived using the IASP91 reference model, where the d410 mean depth is 409.1 km and the d660 is 661.5 km, and the mean MTZ thickness is 251.8 km. This model presents coherent depressions and uplifts of the discontinuities matching well known …

Measurements And Simulation Of Conductor-Related Loss Of Pcb Transmission Lines, Oleg Kashurkin

Masters Theses

"With continuously increasing data rates Signal Integrity (SI) problems become more and more challenging. One of the main issues in high-speed data transfer is the frequency-dependent loss of transmission lines. This thesis is dedicated to conductor-related loss mechanisms in printed circuit board (PCB) transmission lines.

This thesis provides the experimental investigation of conductor properties used for fabrication of PCBs. Particularly, the resistivity and conductivity along with the temperature coefficients of eleven copper types is measured and reported. A four probe measurement technique is used. Results were verified by two independent measurements and show discrepancy of less than 0.5%.

Another major …