Computational Engineering Commons^™

Analysis Of Physicochemical Properties And Terrestrial Dynamics Of Mechanically Formed Micro-Nano Scaled Particles From Agricultural Plastic Mulches, Anton Friedrich Astner

Doctoral Dissertations

Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There exists a need for more representative materials in fundamental studies of …

Direct Calculation Of Configurational Entropy: Pair Correlation Functions And Disorder, Clifton C. Sluss

Doctoral Dissertations

Techniques such as classical molecular dynamics [MD] simulation provide ready access to the thermodynamic data of model material systems. However, the calculation of the Helmholtz and Gibbs free energies remains a difficult task due to the tedious nature of extracting accurate values of the excess entropy from MD simulation data. Thermodynamic integration, a common technique for the calculation of entropy requires numerous simulations across a range of temperatures. Alternative approaches to the direct calculation of entropy based on functionals of pair correlation functions [PCF] have been developed over the years. This work builds upon the functional approach tradition by extending …

Accelerated Catalyst Diffusion In Chemically Amplified Resists, Christopher M. Bottoms

Doctoral Dissertations

Quantitative reaction-diffusion models are critical for the development of high-resolution lithographic processes based on chemically amplified resists (CARs). CARs consist of a glassy polymer resin with a photoacid generator. Patterns are formed through a coupled reaction-diffusion process. It is known that reaction kinetics is controlled by the slow diffusion of acid-anion pairs (catalysts), and catalyst diffusion lengths partly control the pattern resolution and uniformity. However, it is difficult to quantify the diffusivity during reaction, let alone examine the roles of polymer-ion and ion-ion interactions on catalyst mobility, using direct measurements. This work presents a concerted experimental and computational effort to …

X-Means Clustering Implementing The Gap Statistic For Multiple Positron Emission Particle Tracking, Matthew Herald

EURēCA: Exhibition of Undergraduate Research and Creative Achievement

The most efficient and accurate method for clustering Coincidence Lines (CL) for Positron Emission Particle Tracking (PEPT) is undetermined. A number of methods have been created to perform this task. A novel clustering method featuring x-means is presented using an automated k-value estimator for k-means clustering. Gap statistic is used to select the best k-value. Geant4 Application for Tomographic Emission is used to simulate particles of 50 µCi and the detection and electronic chain associated with the Siemens Inveon Pre-Clinical Scanner. The simulation produces an array of coincident lines (CL) in a format consistent with scanner output. The CL are …

Physical Information Incorporated Clustering Techniques And Their Applications In Transportation Information System, Yang Zhang

Doctoral Dissertations

Massive data from different sources are becoming available in transportation field, and spurring new research on utilizing these data to nurture new intelligent transportation information systems. Clustering algorithms are among the methods that are being applied to the domain but facing challenges. Classical clustering algorithms work fine with \point" based data, which are homogeneous and have no extra constraints. Data in transportation are sometimes involved with specific geometric shapes, have underlying constraints, and can be heterogeneous. There has been no clustering algorithm dedicated to these situations.

In this dissertation, we re-examine the mathematical foundation and underlying philosophy of hierarchical, density …

Target Detection With Neural Network Hardware, Hollis Bui, Garrett Massman, Nikolas Spangler, Jalen Tarvin, Luke Bechtel, Kevin Dunn, Shawn Bradford

Chancellor’s Honors Program Projects

No abstract provided.

Improving Predictive Capabilities Of Classical Cascade Theory For Nonproliferation Analysis, David Allen Vermillion

Doctoral Dissertations

Uranium enrichment finds a direct and indispensable function in both peaceful and nonpeaceful nuclear applications. Today, over 99% of enriched uranium is produced by gas centrifuge technology. With the international dissemination of the Zippe archetypal design in 1960 followed by the widespread illicit centrifuge trafficking efforts of the A.Q. Khan network, traditional barriers to enrichment technologies are no longer as effective as they once were. Consequently, gas centrifuge technology is now regarded as a high-priority nuclear proliferation threat, and the international nonproliferation community seeks new avenues to effectively and efficiently respond to this emergent threat.

Effective response first requires an …

Mixed-Mode Dynamic Crack Propagation Using The Discontinuous Galerkin Method, Russell Thomas Hollman

Masters Theses

A recently proposed Discontinuous Galerkin (DG) method for modeling nonlinear fracture mechanics problems in the context of the finite element method is investigated. The DG method provides a framework for fracture mechanics by employing interface elements within the region of interest where cracking is expected. Previous studies have shown that the use of traction-separation laws within the DG method have enhanced stability for dynamic problems by removing the issue of artificial compliance compared to intrinsic cohesive zone elements. The purpose of this thesis is to apply the DG method to a mixed-mode dynamic crack propagation problem, namely the Kalthoff-Winkler experiment. …

Large Scale Brownian Dynamics Simulation Of Dilute And Semidilute Polymeric Solutions, Amir Saadat

Doctoral Dissertations

Excluded Volume (EV) and Hydrodynamic Interactions (HI) play a central role in static and dynamic properties of macromolecules in solution under equilibrium and nonequilibrium settings. The computational cost of incorporating HI in mesoscale Brownian dynamics (BD) simulations, particularly in the semidilute regime has motivated significant research aimed at development of high-fidelity and efficient techniques.

In this study, I have developed several algorithms for the mesoscale bead-spring representation of a macromolecular solution in dilute and semidilute regimes. The Krylov subspace method enables fast calculation of single chain dynamics with simulation time scaling of O(N_b²) [order N …

Lattice Boltzmann Methods For Wind Energy Analysis, Stephen Lloyd Wood

Doctoral Dissertations

An estimate of the United States wind potential conducted in 2011 found that the energy available at an altitude of 80 meters is approximately triple the wind energy available 50 meters above ground. In 2012, 43% of all new electricity generation installed in the U.S. (13.1 GW) came from wind power. The majority of this power, 79%, comes from large utility scale turbines that are being manufactured at unprecedented sizes. Existing wind plants operate with a capacity factor of only approximately 30%. Measurements have shown that the turbulent wake of a turbine persists for many rotor diameters, inducing increased vibration …

Improving Ventricular Catheter Design Through Computational Fluid Dynamics, Sofy Hefets Weisenberg

Masters Theses

Cerebrospinal fluid (CSF) shunts are fully implantable medical devices that are used to treat patients suffering from conditions characterized by elevated intracranial pressure, such as hydrocephalus. In cases of shunt failure or malfunction, patients are often required to endure one or more revision surgeries to replace all or part of the shunt. One of the primary causes of CSF shunt failure is obstruction of the ventricular catheter, a component of the shunt system implanted directly into the brain's ventricular system. This work aims to improve the design of ventricular catheters in order to reduce the incidence of catheter obstruction and …

Data Security And Privacy In Smart Grid, Yue Tong

Doctoral Dissertations

This dissertation explores novel data security and privacy problems in the emerging smart grid.

The need for data security and privacy spans the whole life cycle of the data in the smart grid, across the phases of data acquisition, local processing and archiving, collaborative processing, and finally sharing and archiving. The first two phases happen in the private domains of an individual utility company, where data are collected from the power system and processed at the local facilities. When data are being acquired and processed in the private domain, data security is the most critical concern. The key question is …

From Mpi To Openshmem: Porting Lammps, Chunyan Tang

Masters Theses

This work details the opportunities and challenges of porting a petascale-capable, MPI-based application LAMMPS to OpenSHMEM. We investigate the major programming challenges stemming from the differences in communication semantics, address space organization, and synchronization operations between the two pro- gramming models. This work provides several approaches to solve those challenges for representative communication patterns in LAMMPS, e.g., by utilizing group synchronization, peer’s buffer status tracking, double buffer strategy and unpacked direct transfer of data. The performance of LAMMPS is evaluated on the Titan HPC system at ORNL. The OpenSHMEM implementations are compared with MPI version in terms of both strong …

Using Ab Initio Simulations To Examine The Flexoelectric Effect In Perovskites, Austin B. Plymill

EURēCA: Exhibition of Undergraduate Research and Creative Achievement

Flexoelectricity is a property that dielectric materials exhibit where they produce polarization when subject to an inhomogeneous deformation. In the past, this effect has been largely ignored, as its effect in bulk materials has been much less significant than the related effect of piezoelectricity, the polarization of material due to uniform deformation. Interest in flexoelectricity has been increasing in recent years due to the development of nanotechnologies. Flexoelectricity is proportional to the strain gradient a material is subjected to making the flexoelectric effect immense on the nanoscale. Additionally, the flexoelectric effect scales with the dielectric constant making it have a …

Analytical And Computational Modeling Of Membrane Nanotubes, Sina Mirzaeifard

Masters Theses

This thesis investigates the interplay between cell membranes and the actin cytoskeleton in cellular structures known as membrane nanotubes. Membrane nanotubes are slender membrane structures that physically connect cells over long distances, and experiments suggest that they play a role in transferring material and information between cells. Disrupting the actin cytoskeleton disrupts membrane nanotubes. Although recent studies have revealed insight into the physical properties and functions of membrane-actin systems, further research is needed to understand their behavior in biological contexts. Membrane nanotubes provide a novel system with which to investigate interactions between the cell membrane and actin.

In this thesis, …

Ab Initio Studies Of Proton Transport In Proton Exchange Membranes, Jeffrey Keith Clark

Doctoral Dissertations

A molecular-level understanding of the factors that contribute to transport properties of proton exchange membranes (PEMs) for fuel cell applications is needed to aid in the development of superior membrane materials. Ab initio electronic structure calculations were undertaken on various PEM ionomer fragments to explore the effects of local hydration, side chain connectivity, protogenic group separation, and specific side chain chemistry on proton dissociation and transfer at low hydration. Cooperative interactions between both intra- and inter-molecular acidic groups and hydrogen bond connectivity were found to enhance proton dissociation at very low degrees of hydration. The energetics associated with proton transfer …

Graphics Processing Unit Bloom Filters: Classical And Probabilistic, Joshua Michael Pyle

Masters Theses

Graphics Processing Units (GPUs) have been used to enhance the speed and efficiency of both data structures and algorithms alike. A common data structure used in Computer Science is the Bloom Filter, which is used in many types of applications including databases and security logging. The Bloom Filter is a lossy data structure that uses several hash functions to store keys into a bit array. A novel, new Bloom Filter meant for use in internet traffic detection called the Probabilistic Bloom Filter has recently been developed. In practice, this new Bloom Filter typically makes use of more hash functions than …

Adsorption And Diffusion Of Gases In Nano-Porous Materials, Nethika Sahani Suraweera

Doctoral Dissertations

In this work, a systematic computational study directed toward developing a molecular-level understanding of gas adsorption and diffusion characteristics in nano-porous materials is presented. Two different types of porous adsorbents were studied, one crystalline and the other amorphous. Physisorption and diffusion of hydrogen in ten iso-reticular metal-organic frameworks (IRMOFs) were investigated. A set of nine adsorbents taken from a class of novel, amorphous nano-porous materials composed of spherosilicate building blocks and isolated metal sites was also studied, with attention paid to the adsorptive and diffusive behavior of hydrogen, methane, carbon dioxide and their binary mixtures. Both classes of materials were …

Effects Of Data Resolution And Human Behavior On Large Scale Evacuation Simulations, Wei Lu

Doctoral Dissertations

Traffic Analysis Zones (TAZ) based macroscopic simulation studies are mostly applied in evacuation planning and operation areas. The large size in TAZ and aggregated information of macroscopic simulation underestimate the real evacuation performance. To take advantage of the high resolution demographic data LandScan USA (the zone size is much smaller than TAZ) and agent-based microscopic traffic simulation models, many new problems appeared and novel solutions are needed. A series of studies are conducted using LandScan USA Population Cells (LPC) data for evacuation assignments with different network configurations, travel demand models, and travelers’ compliance behavior.

First, a new Multiple-Source-Nearest-Destination Shortest Path …

Bayesian Dictionary Learning For Single And Coupled Feature Spaces, Li He

Doctoral Dissertations

Over-complete bases offer the flexibility to represent much wider range of signals with more elementary basis atoms than signal dimension. The use of over-complete dictionaries for sparse representation has been a new trend recently and has increasingly become recognized as providing high performance for applications such as denoise, image super-resolution, inpaiting, compression, blind source separation and linear unmixing. This dissertation studies the dictionary learning for single or coupled feature spaces and its application in image restoration tasks. A Bayesian strategy using a beta process prior is applied to solve both problems.

Firstly, we illustrate how to generalize the existing beta …

Essentially Analytical Theory Closure For Space Filtered Thermal-Incompressible Navier-Stokes Partial Differential Equation System On Bounded Domains, Mikhail Alexandrovich Sekachev

Doctoral Dissertations

Numerical simulation of turbulent flows is identified as one of the grand challenges in high-performance computing. The straight forward approach of solving the Navier-Stokes (NS) equations is termed Direct Numerical Simulation (DNS). In DNS the majority of computational effort is spent on resolving the smallest scales of turbulence, which makes this approach impractical for most industrial applications even on present-day supercomputers. A more feasible approach termed Large Eddy Simulation (LES) has evolved over the last five decades to facilitate turbulent flow predictions for reasonable Reynolds (Re) numbers and domain sizes. LES theory uses the concept of convolution with a spatial …

Kernel-Assisted And Topology-Aware Mpi Collective Communication Among Multicore Or Many-Core Clusters, Teng Ma

Doctoral Dissertations

Multicore or many-core clusters have become the most prominent form of High Performance Computing (HPC) systems. Hardware complexity and hierarchies not only exist in the inter-node layer, i.e., hierarchical networks, but also exist in internals of multicore compute nodes, e.g., Non Uniform Memory Accesses (NUMA), network-style interconnect, and memory and shared cache hierarchies.

Message Passing Interface (MPI), the most widely adopted in the HPC communities, suffers from decreased performance and portability due to increased hardware complexity of multiple levels. We identified three critical issues specific to collective communication: The first problem arises from the gap between logical collective topologies and …

A Validation Study Of The Amp Nuclear Fuel Performance Code, Aaron Martin Phillippe

Masters Theses

The Advanced Multi-Physics (AMP) Fuel Performance Code is a fully coupled, 3-dimensional (3D) code currently in development at the Oak Ridge National Laboratory (ORNL) for the purposes of advanced fuel performance evaluation and simulation. The purpose of this study was to investigate and examine the capabilities of AMP, as developed so far, in thermo-mechanical evaluations of experimental benchmark data. The IFA-432 and IFA-597 datasets from the Nuclear Energy Agency’s (NEA) International Fuel Performance Experiments (IFPE) database were examined, and a code-to-code comparison made against FRAPCON-3.4, a one dimensional (1D) code used by the Nuclear Regulatory Commission (NRC) for fuel licensing. …

Development And Verification Of A Navier-Stokes Solver With Vorticity Confinement Using Openfoam, Austin Barrett Kimbrell

Masters Theses

Vorticity Confinement (VC) is a numerical technique which enhances computation of fluid flows by acting as negative diffusion within the limit of vortical regions, preventing the inherent numerical dissipation present with conventional methods. VC shares similarities with large eddy simulation (LES), but its behavior is based on a stable negative dissipation of vortical structures controlled by the automatic balance between two parameters, μ [mu] and ε [epsilon].

In this thesis, three-dimensional, parallel-computing Navier-Stokes solvers with VC are developed using the OpenFOAM computational framework. OpenFOAM is an open-source collection of C++ libraries developed for computational fluid dynamics. Object-oriented programming concepts are …

Micromechanical Studies Of Intergranular Strain And Lattice Misorientation Fields And Comparisons To Advanced Diffraction Measurements, Lili Zheng

Doctoral Dissertations

Inhomogeneous deformation fields arising from the grain-grain interactions in polycrystalline materials have been evaluated using a crystal plasticity finite element method and extensively compared to neutron diffraction measurements under fatigue crack growth conditions. The roles of intergranular deformation anisotropy, grain boundary damage, and non-common deformation mechanisms (such as twinning for hexagonal close packed crystals) are systematically evaluated. The lattice misorientation field can be used to determine the intragranular deformation behavior in polycrystals or to describe the deformation inhomogeneity due to dislocation plasticity in single crystals. The study of indentation-induced lattice misorientation fields in single crystals sheds lights on the understanding …

A Low Communication Condensation-Based Linear System Solver Utilizing Cramer's Rule, Kenneth C Habgood

Doctoral Dissertations

Systems of linear equations are central to many science and engineering application domains. Given the abundance of low-cost parallel processing fabrics, the study of fast and accurate parallel algorithms for solving such systems is receiving attention. Fast linear solvers generally use a form of LU factorization. These methods face challenges with workload distribution and communication overhead that hinder their application in a true broadcast communication environment.

Presented is an efficient framework for solving large-scale linear systems by means of a novel utilization of Cramer's rule. While the latter is often perceived to be impractical when considered for large systems, it …

Pin-Wise Loading Optimization And Lattice–To-Core Coupling For Isotopic Management In Light Water Reactors, Hermilo Hernandez Noyola

Doctoral Dissertations

A generalized software capability has been developed for the pin-wise loading optimization of light water reactor (LWR) fuel lattices with the enhanced flexibility of control variables that characterize heterogeneous or blended target pins loaded with non-standard compositions, such as minor actinides (MAs). Furthermore, this study has developed the software coupling to evaluate the performance of optimized lattices outside their reflective boundary conditions and within the realistic three-dimensional core-wide environment of a LWR.

The illustration of the methodologies and software tools developed helps provide a deeper understanding of the behavior of optimized lattices within a full core environment. The practical applications …

Propagation Of Periodic Waves Using Wave Confinement, Paula Cysneiros Sanematsu

Masters Theses

This thesis studies the behavior of the Eulerian scheme, with "Wave Confinement" (WC), when propagating periodic waves. WC is a recently developed method that was derived from the scheme "vorticity confinement" used in fluid mechanics, and it efficiently solves the linear wave equation. This new method is applicable for numerous simulations such as radio wave propagation, target detection, cell phone and satellite communications.

The WC scheme adds a nonlinear term to the discrete wave equation that adds stability with negative and positive diffusion, conserves integral quantities such as total amplitude and wave speed, and it allows wave propagation over long …

Molecular Simulations Of Adsorption And Diffusion In Metal-Organic Frameworks (Mofs), Ruichang Xiong

Doctoral Dissertations

Metal-organic frameworks (MOFs) are a new class of nanoporous materials that have received great interest since they were first synthesized in the late 1990s. Practical applications of MOFs are continuously being discovered as a better understanding of the properties of materials adsorbed within the nanopores of MOFs emerges. One such potential application is as a component of an explosive-sensing system. Another potential application is for hydrogen storage.

This work is focused on tailoring MOFs to adsorb/desorb the explosive, RDX. Classical grand canonical Monte Carlo (GCMC) and molecular dynamic (MD) simulations have been performed to calculate adsorption isotherms and self-diffusivities of …