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Articles 1  30 of 402
FullText Articles in Physics
A Study On Homogeneous Sheared Stably Stratified Turbulence, Gavin Portwood
A Study On Homogeneous Sheared Stably Stratified Turbulence, Gavin Portwood
Doctoral Dissertations
Homogeneous sheared and stably stratified turbulence is considered as a fundamental flow relevant to the study of geophysical turbulence and, generally, anisotropic turbulence. Numerical experiments are performed via high resolution direct numerical simulation (DNS) in a geophysicallyrelevant parameter space previously inaccessible to simulation. Turbulent dynamics relevant to the modeling of geophysical hydrodynamics are investigated as a function of mean flow and fluid parameters.
An active tuning scheme is implemented to induce temporally stationary turbulent kinetic energy in order to evaluate turbulence that is statistically independent of initial conditions and spatiotemporally homogeneous. Subject to this constraint, the parametric dependence of the ...
Investigating Blast Fume Propagation, Concentration And Clearance In Underground Mines Using Computational Fluid Dynamics (Cfd), Raymond Ninnang Tiile
Investigating Blast Fume Propagation, Concentration And Clearance In Underground Mines Using Computational Fluid Dynamics (Cfd), Raymond Ninnang Tiile
Doctoral Dissertations
"Blasting activities using standard industry explosives is an essential component of underground hard rock mining operations. Blasting operations result in the release of noxious gases, presenting both safety and productivity threats. Overestimation of postblast reentry time results in production losses, while underestimation leads to injuries and fatalities. Research shows that most underground mines simply standardize postblast reentry times based on experiences and observations. Few underground mines use theoretical methods for calculating postblast reentry time. These theoretical methods, however, are unable to account for the variations in the blasting conditions. Literature review shows that: (i) there is currently no means of ...
Ferrite Characterization Techniques & Particle Simulations For Semiconductor Devices, Nicholas Erickson
Ferrite Characterization Techniques & Particle Simulations For Semiconductor Devices, Nicholas Erickson
Doctoral Dissertations
"This dissertation is divided into three papers, covering two major topics. The first topic, techniques for ferrite characterization, is discussed over the course of two papers. The second topic, particle simulations for semiconductor devices, is discussed in the last paper. In the first paper, the method for extracting permeability from ferrite materials is discussed for the Keysight 16454A permeability extraction fixture, where the ferrite material to be characterized is assumed to be homogeneous. Then the method is updated to account for layered materials. The updated method is verified through fullwave simulations. In the second paper, a planar printed circuit board ...
Decoding The History Of The Early Solar System Using Comet Volatile Compositions, Nathaniel Xavier Roth
Decoding The History Of The Early Solar System Using Comet Volatile Compositions, Nathaniel Xavier Roth
Doctoral Dissertations
"Understanding the evolution of the solar system, as well as its current volatile content, requires knowledge of the initial conditions present in the solar nebula. As some of the first objects to accrete in the solar nebula, cometary nuclei are among the most primitive remnants of solar system formation, and their presentday volatile composition likely reflects the composition and conditions where (and when) they formed. As such, the volatile compositions of cometary nuclei may serve as 'fossils' of solar system formation. Highresolution nearinfrared spectroscopy offers a valuable tool for sampling the primary volatile (i.e., ices subliming directly from the ...
Coherent Effects In Wave Propagation Through Complex Media, Milan Koirala
Coherent Effects In Wave Propagation Through Complex Media, Milan Koirala
Doctoral Dissertations
"Diffusion is a powerful and versatile description of a typical wave propagation in a random scattering medium that disregards phase and, thus, a possibility of interference. Speckle, transmission fluctuations, wave localization, nonlocal correlations, and transmission eigenchannels are examples of persistent interference effects, which arise in the course of deterministic propagation. Such wave phenomena contain a wealth of information about the medium and the source of waves, enabling sensing and coherent control of the propagation. The nonlocal correlations and speckle statistics of the partially coherent light are used to uncover an object hidden by a diffusive cloak inside a strong scattering ...
Electromagnetic WaveMatter Interactions In Complex OptoElectronic Materials And Devices, Raj Kumar Vinnakota
Electromagnetic WaveMatter Interactions In Complex OptoElectronic Materials And Devices, Raj Kumar Vinnakota
Doctoral Dissertations
This dissertation explores the fundamentals of lightmatter interaction towards applications in the field of Optoelectronic and plasmonic devices. In its core, this dissertation attempts and succeeds in the the modeling of lightmatter interactions, which is of high importance for better understanding the rich physics underlying the dynamics of electromagnetic field interactions with charged particles. Here, we have developed a selfconsistent multiphysics model of electromagnetism, semiconductor physics and thermal effects which can be readily applied to the field of plasmotronics and Selective Laser Melting (SLM). Plasmotronics; a subfield of photonics has experienced a renaissance in recent years by providing a large ...
Effective Magnetic And Electric Response Of Composite Materials, Mona Hassan Alsaleh
Effective Magnetic And Electric Response Of Composite Materials, Mona Hassan Alsaleh
Doctoral Dissertations
Metamaterials (MMs) are nanocomposite materials consisting of metaldielectric resonators much smaller in size than the wavelength of the incident light. Common examples of metamaterials are based on split ring resonators (SRRs), parallel wires or strips and fishnet structures. These types of materials are designed and fabricated in order to provide unique optical responses to the incident electromagnetic radiation that are not available in naturally existing materials. The MMs can exhibit unusual properties such as strong magnetism at terahertz (THz) and optical frequencies. Additionally, negative index materials (NIMs) can provide negative index of refraction which can be used in many applications ...
Characterization Of The Cylinderical Split InternalLoop Photobioreactor With Scenedesmus Microalgae: Advanced Culturing, Modeling, And Hydrodynamics, Laith S. Sabri
Doctoral Dissertations
"Microalgae are fast growing photoynthetic microorganisms and it have very wide range of industrial applications such as biofuels and wastewater treatment. These cells can be grown in a wide variety of systems ranging from open culture systems (e.g., ponds) to closed culture systems of photobioreactor (e.g., airlift). The open culture systems exist in the external environment, and hence, are not intrinsically controllable. However, the microalgae production in enclosed photobioreactors faces prohibitively high production costs with special difficulty in reactor design and scaleup. The light availability and utilization efficiency in the photobioreactor in terms of design and scaleup consider ...
Fully Differential Study Of Dissociative Capture In P + H₂ Collisions, Basu Ram Lamichhane
Fully Differential Study Of Dissociative Capture In P + H₂ Collisions, Basu Ram Lamichhane
Doctoral Dissertations
"In recent years, the key role of the projectile coherence properties has been studied in several ionatom scattering processes. These studies strongly suggested that cross sections could be significantly affected by the projectile coherence properties, especially for fast, heavy ions. In the present study, we used such coherence effects as a tool to sensitively analyze the few body dynamics of the scattering process. To this end, we performed three kinematically complete experiments on fragmentation of H_{2} by 75 keV proton impacts. A novel approach was used to analyze coherence and interference effects in the observed crosssections. The idea was ...
FirstPrinciple Approaches To Strongly Correlated Quantum Spin Systems, Yuan Huang
FirstPrinciple Approaches To Strongly Correlated Quantum Spin Systems, Yuan Huang
Doctoral Dissertations
My Ph.D. research focuses on the numerical study of two quantum spin systems, one is the squarelattice Heisenberg antiferromagnet with ringexchange interaction at the Neel to valencebond solid state transition, which is proposed to be described by the theory of deconfined criticality; the other is the highly frustrated pyrochlore Heisenberg antiferromagnet. Both systems are known as prototypical candidates for the exotic spinliquid state with emergent fractionalized excitations and gauge structure. Regarding the long standing controversy of deconfined criticality, our results conclude that the deconfined critical theory capture the essence of the Neel to valencebond solid state transition at least ...
Search For LongLived, Massive Particles Decaying Into Dimuon Vertices In Pp Collisions At 13 Tev With The Atlas Detector At The Lhc, Nathan Bernard
Search For LongLived, Massive Particles Decaying Into Dimuon Vertices In Pp Collisions At 13 Tev With The Atlas Detector At The Lhc, Nathan Bernard
Doctoral Dissertations
A search for longlived, massive particles decaying into dimuon pairs, in 32.9 fb^{1} of data analyzed from the ATLAS detector is presented. Two signal models are considered: GGM SUSY, where the long lived particle mass is between 3001000 GeV, and the dark photon model, where the Z_{D} mass is between 2060 GeV. An excess over the predicted background is observed in the GGM channel, however the angular/kinematic distributions of the excess vertices are consistent with a detec tor/conditions related issue. A modified selection is used for the GGM channel which increases the signal sensitivity. 95 ...
Emergent Phenomena In Quantum Critical Systems, Kun Chen
Emergent Phenomena In Quantum Critical Systems, Kun Chen
Doctoral Dissertations
A quantum critical point (QCP) is a point in the phase diagram of quantum matter where a continuous phase transition takes place at zero temperature. Lowdimensional quantum critical systems are strongly correlated, therefore hosting nontrivial emergent phenomena. In this thesis, we first address two decadesold problems on quantum critical dynamics. We then reveal two novel emergent phenomena of quantum critical impurity problems. In the first part of the thesis, we address the linear response dynamics of the $(2+1)$dimensional $O(2)$ quantum critical universality class, which can be realized in the ultracold bosonic system near the superfluid (SF) to ...
Dynamics And Structure Of Polyelectrolyte Complexes, Hamidreza ShojaeiMahib
Dynamics And Structure Of Polyelectrolyte Complexes, Hamidreza ShojaeiMahib
Doctoral Dissertations
Interaction of charged macromolecules among themselves and with charged interfaces in salty aqueous medium is a common phenomenon prevalent in biology and synthetic systems. We have addressed several interrelated issues in this general context. First we present a theory of adsorption of polyelectrolytes on the interior and exterior surfaces of a charged spherical vesicle. We derive the critical adsorption condition and the density profile of the polymer in terms of various characteristics of the polymer, vesicle, and the solution, such as the length and charge density of polymer, the radius and charge of the vesicle, the salt concentration of the ...
Preparation, Mechanics And Structure Of Sphere Packings Near The Random Loose Packing Limit, Greg Robert Farrell
Preparation, Mechanics And Structure Of Sphere Packings Near The Random Loose Packing Limit, Greg Robert Farrell
Doctoral Dissertations
Packings of monodisperse, hard spheres serve as an important model system in the understanding of granular materials which are ubiquitous in nature and industry from sedimented river beds, to construction aggregates, to pharmaceuticals. Unlike frictionless hard spheres which are only stable at densities near the random close packing volume fraction, packings of real spheres form stable packings over a range of volume fractions. We report experimental investigations of sedimented packings of noncohesive polymethylmethacrylate spheres over a range of volume fractions near the lower limit of this range of volume fractions.
We create packings by slow sedimentation in a viscous fluid ...
SelfAssembling Networks In Soft Materials, Ishan Prasad
SelfAssembling Networks In Soft Materials, Ishan Prasad
Doctoral Dissertations
This dissertation presents a study on heterogeneous network structure in two distinct classes of soft material systems: disordered assemblies of jammed binary spheres and ordered morphologies of block copolymer melts. The aim is to investigate the combined role of geometry and entropy in structure formation of soft matter assemblies. First, we investigate the influence of particle size asymmetry on structural properties of jammed binary sphere mixtures. We give evidence of two distinct classes of materials separated by a critical size ratio that marks the onset of a sharp transition due to simultaneous jamming of a subcomponent of the packing. We ...
Vibrated Squares As Equilibrium And Active Matter, Lee Askew Walsh
Vibrated Squares As Equilibrium And Active Matter, Lee Askew Walsh
Doctoral Dissertations
We study the effects of particle shape and selfpropulsion on the collective behaviors of a twodimensional granular fluid, using an experimental system of hard square grains. We energize the system by vibration, which, depending on particle shape, induces either isotropic diffusion or persistent selfpropulsion in the particles. We use specially designed grains as a model system to study (i) the equilibrium packing of hard squares in two dimensions, (ii) the dynamics of athermal selfpropelled particles, and (iii) the melting kinetics of an unconfined granular crystallite.
The first study concerns the phase diagram of a twodimensional fluid of hard squares, which ...
Quantum Phase Transitions In Disordered Boson Systems, Zhiyuan Yao
Quantum Phase Transitions In Disordered Boson Systems, Zhiyuan Yao
Doctoral Dissertations
In this dissertation, we study the superfluidinsulator quantum phase transition in disordered boson systems. Recently, there has been considerable controversy over the validity of the scaling relations of the superfluidBoseglass quantum phase transition in three dimensions. Results from experimental and numerical studies on disordered quantum magnets contradict the scaling relations and the associated conventional scaling hypothesis for the singular part of the free energy. We determine various critical exponents of the superfluidBoseglass quantum phase transition in threedimensional disordered BoseHubbard model through extensive Monte Carlo simulations. Our numerical study shows the previous studies on disordered quantum magnets were performed outside the ...
Parallel Algorithms For Time Dependent Density Functional Theory In RealSpace And RealTime, James Kestyn
Parallel Algorithms For Time Dependent Density Functional Theory In RealSpace And RealTime, James Kestyn
Doctoral Dissertations
Density functional theory (DFT) and time dependent density functional theory (TDDFT) have had great success solving for ground state and excited states properties of molecules, solids and nanostructures. However, these problems are particularly hard to scale. Both the size of the discrete system and the number of needed eigenstates increase with the number of electrons. A complete parallel framework for DFT and TDDFT calculations applied to molecules and nanostructures is presented in this dissertation. This includes the development of custom numerical algorithms for eigenvalue problems and linear systems. New functionality in the FEAST eigenvalue solver presents an additional level of ...
Collider Tests Of Fundamental Symmetries And Neutrino Properties, Haolin Li
Collider Tests Of Fundamental Symmetries And Neutrino Properties, Haolin Li
Doctoral Dissertations
The CP parity of the Higgs boson and the details of the electroweak symmetry breaking are the two crucial ingredients to understand the matterantimatter asymmetry in our universe. Electroweak baryogenesis is an intriguing solution to the puzzle of this unexplained observed asymmetry because of its testability at present and near future collider experiments. The possibilities of testing CP phase in the TwoHiggsDoublets Models (2HDMs) and the generation of a strong firstorder electroweak phase transition (SFOEWPT) in the real singlet model at the future high luminosity LHC are studied. In addition to the specific extensions to the Standard Model (SM), I ...
Equilibrium Partitioning Of Binary Polymer Mixtures Into Biological Nanopores, Mehmet Alphan Aksoyoglu
Equilibrium Partitioning Of Binary Polymer Mixtures Into Biological Nanopores, Mehmet Alphan Aksoyoglu
Doctoral Dissertations
The cell interior, enclosed by membrane barriers, is a condensed solution of inorganic ions, polymers, carbohydrates, polynucleotides, and a large number of other organic molecules. Within cells, transport of metabolites and biopolymers, such as polynucleotides and proteins, occurs partly through specific transmembrane pores (mesoscopic ion channels) spanning cellular compartments. Examples of such functions are translocation of matrix RNA molecules from cell nucleus through nuclear pore complexes, ejection of viral genome from bacterial virus capsids into host bacterial cells, and translocation of protein factors across toxin channels in biological membranes. All these processes, that occur in the cellular milieu, are mediated ...
Geometry, Growth And Pattern Formation In Thin Elastic Structures, Salem AlMosleh
Geometry, Growth And Pattern Formation In Thin Elastic Structures, Salem AlMosleh
Doctoral Dissertations
Thin shells are abundant in nature and industry, from atomic to planetary scales. The mechanical behavior of a thin shell depends crucially on its geometry and embedding in 3 dimensions (3D). In fact, the behavior of extremely thin shells becomes scale independent and only depends on geometry. That is why the crumpling of graphene will have similarities to the crumpling of paper. In this thesis, we start by discussing the static behavior of thin shells, highlighting the role of asymptotic curves (curves with zero normal curvature) in determining the possible deformations and in controlling the folding patterns. In particular, we ...
Reduced Models Of Point Vortex Systems In Quasigeostrophic Fluid Dynamics, Jonathan Maack
Reduced Models Of Point Vortex Systems In Quasigeostrophic Fluid Dynamics, Jonathan Maack
Doctoral Dissertations
We develop a nonequilibrium statistical mechanical description of the evolution of point vortex systems governed by either the Euler, singlelayer quasigeostrophic or twolayer quasigeostrophic equations. Our approach is based on a recently proposed optimal closure procedure for deriving reduced models of Hamiltonian systems. In this theory the statistical evolution is kept within a parametric family of distributions based on the resolved variables chosen to describe the macrostate of the system. The approximate evolution is matched as closely as possible to the true evolution by minimizing the meansquared residual in the Liouville equation, a metric which quantifies the information loss rate ...
Measured Capillary Forces On Spheres At Liquid Interfaces And The Mechanics Of Interfacial Particulate Assemblies, Wei He
Doctoral Dissertations
Particleladen interfaces have promising potentials in many fields because the particulate nature can endow the surface with physical properties that are not readily obtained from molecularscale surfactants. In this dissertation, we first focus on measuring capillary forces on particles at fluid interfaces in order to assess the key parameters that yield effective stabilizing particles. In experiment, the force and the displacement of a millimeterscale particle passing through a liquid interface were recorded. We find that the peak force needed to detach a particle from an interface crowded with other particles is consistently smaller than the force at a clean interface ...
Alpha Radiation Studies And Related Backgrounds In The Darkside50 Detector, Alissa Monte
Alpha Radiation Studies And Related Backgrounds In The Darkside50 Detector, Alissa Monte
Doctoral Dissertations
DarkSide50 is the current phase of the DarkSide direct dark matter search program, operating underground at the Laboratori Nazionali del Gran Sasso in Italy. The detector is a dualphase argon Time Projection Chamber (TPC), designed for direct detection of Weakly Interacting Massive Particles (WIMPs), and housed within a veto system of liquid scintillator and water Cherenkov detectors. Since switching to a target of low radioactivity argon extracted from underground sources in April 2015, the background is no longer dominated by naturally occurring 39Ar. However, alpha backgrounds from radon and its daughters remain, both from the liquid argon bulk and internal ...
Evolving Specialization In An AgentBased Model Without TaskSwitching Costs, Shane Robert Meyer
Evolving Specialization In An AgentBased Model Without TaskSwitching Costs, Shane Robert Meyer
Doctoral Dissertations
"This work examines the possibility of evolving the phenotypic specialization associated with division of labor in an agentbased model without taskswitching costs. The model examines two groups competing for vital resources, where members of one group are capable of sharing resources with other agents in their group. Agents attempt to collect resources which allow them to reproduce, with more resources leading to a greater number of offspring by asexual reproduction. Four variants of the model are examined, with combinations of one or two resources and the presence of a foraging risk. The presence of the foraging risk can lead to ...
Nanoporous Carbon Scaffolds For Energy Storage Applications, Waruni Jayawardana
Nanoporous Carbon Scaffolds For Energy Storage Applications, Waruni Jayawardana
Doctoral Dissertations
"Nanoporous carbons (NCs) have become increasingly popular in various fields of research due to their unique properties including tunable pore sizes, higher pore volumes and higher surface areas, as well as being able to produce controlled nanostructures. The work presented here uses NC scaffolds with as active hosts for (1) Liion battery electrodes and (2) confined metal hydrides (MH) for hydrogen storage applications. In (1) we investigate the Li diffusion characteristics in hard carbons (HCs) that are important for electrochemical applications. We develop a novel method named VoltageRelaxation Galvanostatic Intermittent Titration Technique (VRGITT). Parameters derived from the fitting of electrochemical ...
Correlation Between Delay Time And Measured Concentration And Concentration Uncertainty By Neutron Activation Analysis, James Thomas Seman
Correlation Between Delay Time And Measured Concentration And Concentration Uncertainty By Neutron Activation Analysis, James Thomas Seman
Doctoral Dissertations
"For the last several decades, it has been apparent that new methods of identifying explosives can help investigators trace their origins. One way to identify an explosive is through the use of taggants: materials added to a product that encodes information about the product such as when it was manufactured.
This research investigates the survivability of a new identification taggant called the Nuclear Barcode that overcomes some of the downfalls that have been identified in prior taggants. The Nuclear Barcode encodes information as a unique combination of concentrations of rare earths (Ho, Eu, Sm, Lu, and Dy) and precious metals ...
Modeling And Characterization Of ThermoOxidative Behavior Of Bismaleimide Composites, Rafid Muhammad Hussein
Modeling And Characterization Of ThermoOxidative Behavior Of Bismaleimide Composites, Rafid Muhammad Hussein
Doctoral Dissertations
"Hightemperature polymer matrix composites (HTPMCs) are susceptible to thermooxidation, which accelerates the composites' degradation and reduces the service life. Mechanical properties of HTPMCs deteriorate due to coupled thermooxidation and crosslinking mechanisms. Bismaleimides (BMIs) are commonly used hightemperature resins for aerospace applications. This work presents the viability of using experimental weight loss to model the spatial distribution of oxidation when the oxidized polymer matrix is not discernible. Three tasks are introduced: (1) Anisotropic oxidation prediction using optimized weight loss behavior of bismaleimide composites, (2) A multiscale modeling of thermooxidative effects on the flexural behavior of crossply bismaleimide composites, and (3) Thermooxidative ...
Disorder At FirstOrder Classical And Quantum Phase Transitions, Ahmed Khalil Ibrahim
Disorder At FirstOrder Classical And Quantum Phase Transitions, Ahmed Khalil Ibrahim
Doctoral Dissertations
"This dissertation studies the effects of quenched disorder on classical, quantum and nonequilibrium phase transitions. After a short introduction which covers the basic concepts of phase transitions, finitesize scaling and random disorder, the dissertation focuses on four separate but related projects. First, we investigate the influence of quenched disorder with longrange spatial correlations on the nonequilibrium phase transitions in the contact process. We show that the longrange correlations increase the probability to find rare atypical regions in the sample. This leads to enhanced Griffiths singularities and changes the universality class of the transition.
Project 2 and 3 focus on disorder ...
Analysis Of Primary Stripper Foils At The Spallation Neutron Source By An Electron Beam Foil Test Stand, Eric Paul Barrowclough
Analysis Of Primary Stripper Foils At The Spallation Neutron Source By An Electron Beam Foil Test Stand, Eric Paul Barrowclough
Doctoral Dissertations
Diamond films are used at the Spallation Neutron Source (SNS) as the primary charge exchange foils (i.e., stripper foils) of the accelerated 1 GeV (Gigaelectron volts) hydride ions. The most common type of film used is a nanocrystalline diamond film, typically 17 mm x 45 mm (millimeter) with an aerial density of 350 μg/cm^{2} (microgram per square centimeter). The diamond film is deposited on a corrugated silicon substrate using plasmaassisted chemical vapor deposition. After the growth of the diamond film, 30 mm of the silicon substrate is etched away, leaving a freestanding diamond foil with a silicon ...