Digital Commons Network^™

Equalization Of Loudspeakers And Enclosed Sound Fields, Xi Chen

Theses and Dissertations

Equalization of loudspeakers and enclosed sound fields has been a topic of considerable interest for decades. Confusion has often arisen among audio professionals regarding the feasibility of simultaneously equalizing a loudspeaker and the enclosed field (i.e., the “room”) it excites. Because of frustrations encountered in such efforts, some have advocated abandoning simultaneous equalization altogether. This dissertation discusses the drawbacks of this approach as well as traditional in situ equalization methods. It demonstrates that many problems with traditional equalization stem from the use of measured acoustic pressure at a discrete point in a sound field as the system output. The dissertation …

Carbon Coated Tellurium For Optical Data Storage, Jonathan D. Abbott

Theses and Dissertations

A highly durable optical disk has been developed for data archiving. This optical disk uses tellurium as the write layer and carbon as a dielectric and oxidation prevention layer. The sandwich style CTeC film was deposited on polycarbonate and silicon substrates by plasma sputtering. These films were then characterized with SEM, TEM, EELS, ellipsometry, ToF-SIMS, etc, and were tested for writability and longevity. Results show the films were uniform in physical structure, are stable, and able to form permanent pits. Data was written to a disk and successfully read back in a commercial DVD drive.

Analysis Of Expedient Field Decontamination Methods For The Xmx/2l-Mil High-Volume Aerosol Sampler, Brandon C. Laroche

Theses and Dissertations

The XMX/2L-MIL is a high volume air sampler used by the Air Force Bioenvironmental Engineering community to collect biological aerosols. Without a verified decontamination technique, however, the XMX cannot be used effectively. The objective of this study was to evaluate several proposed methods for expedient field decontamination of the XMX. This study centered on the inactivation of Bacillus atrophaeus spores and vegetative Erwinia herbicola organisms from the XMX inner canister. The goals in this investigation were twofold: 1) to verify the antimicrobial efficacy of a 10% bleach solution and 2) to determine if wiping the components with a bleach-soaked paper …

Midwave Infrared Imaging Fourier Transform Spectrometry Of Combustion Plumes, Kenneth C. Bradley

Theses and Dissertations

A midwave infrared (MWIR) imaging Fourier transform spectrometer (IFTS) was used to successfully capture and analyze hyperspectral imagery of combustion plumes. Jet engine exhaust data from a small turbojet engine burning diesel fuel at a flow rate of 300 cm³/min was collected at 1 cm⁻¹ resolution from a side-plume vantage point on a 200x64 pixel window at a range of 11.2 meters. Spectral features of water, CO, and CO² were present, and showed spatial variability within the plume structure. An array of thermocouple probes was positioned within the plume to aid in temperature analysis. A single-temperature …

Nanoscopic Investigation Of Surface Morphology Of Neural Growth Cones And Indium Containing Group-Iii Nitrides, Göksel Durkaya

Physics and Astronomy Dissertations

This research focuses on the nanoscopic investigation of the three-dimensional surface morphology of the neural growth cones from the snail Helisoma trivolvis, and InN and InGaN semiconductor material systems using Atomic Force Microscopy (AFM). In the analysis of the growth cones, the results obtained from AFM experiments have been used to construct a 3D architecture model for filopodia. The filopodia from B5 and B19 neurons have exhibited different tapering mechanisms. The volumetric analysis has been used to estimate free Ca2+ concentration in the filopodium. The Phase Contrast Microscopy (PCM) images of the growth cones have been corrected to thickness provided …

Analysis Of Gan/Alxga1?Xn Heterojunction Dual-Band Photodetectors Using Capacitance Profiling Techniques, Laura E. Byrum

Physics and Astronomy Theses

Capacitance-voltage-frequency measurements on n+-GaN/AlxGa1−xN UV/IR dual-band detectors are reported. The presence of shallow Si-donor, deep Si-donor, and C-donor/N-vacancy defect states were found to significantly alter the electrical characteristics of the detectors. The barrier Al fraction was found to change the position of the interface defect states relative to the Fermi level. The sample with Al fraction of 0.1 shows a distinct capacitance-step and hysteresis, which is attributed to C-donor/N-vacancy electron trap states located above the Fermi level (200 meV) at the heterointerface; whereas, the sample with Al fraction of 0.026 shows negative capacitance and dispersion, indicating C-donor/N-vacancy and deep Si-donor …

Open Heavy Flavor Measurement At Forward Angles For Cu+Cu Collisions At Center Of Mass Nn Collision Energy 200 Gev, Irakli Garishvili

Doctoral Dissertations

The main purpose of Relativistic Heavy Ion Collider (RHIC) program is to study the Quark-Gluon Plasma (QGP), a deconfined state of matter believed to be created in ultra-relativistic heavy ion collisions. Heavy quarks, expected to be produced during the earlier stages of heavy ion collisions, serve as an important probe of the QGP.‎

‎The following dissertation presents measurements of single muons resulting from the semileptonic decay of heavy flavor quarks in the rapidity range of $1.4 < \vert\eta\vert < 1.9$ for Cu+Cu nuclei collisions at $\sqrt{s_{NN}}=200$ GeV measured by the PHENIX experiment. Single muon spectra were measured for three different centrality classes (0 - 20 \% , 20 - 40 \%, 40 - 94 \%) within the $p_{T}$ range of 1.0 - 4.0 GeV/c.‎

‎To calculate single muon spectra, a full background estimate was statistically subtracted from inclusive spectra of muon candidate tracks reconstructed in the PHENIX muon …

Beta-Decay, Beta-Delayed Neutron Emission And Isomer Studies Around 78Ni, Mustafa Moiz Rajabali

Doctoral Dissertations

A study of nuclei with few nucleons outside the closed shell provides benchmarks for the nuclear shell model especially in this modern era of physics where exotic doubly magic nuclei can be tested. The subject of this thesis is to experimentally investigate the properties of nuclei near ⁷⁸Ni and to confront them with the predictions of modern large scale shell model calculations. In this regard, an experiment was performed at the National Superconducting Cyclotron Laboratory (NSCL) to measure excited states in ^71-73Ni populated via the beta-decay of ^71-73Co. Data collected from this experiment lead to partial level …

Controlled Self-Organization And Tunable Collective Phenomena In Surface-Based Nanostructures, Eun Ju Moon

Doctoral Dissertations

Nanostructure systems possessing certain desirable features can arise from the self-organization of fundamental building blocks. In this thesis we explore two types of controlled self-assembly mechanisms in hetero-epitaxy: (a) classical assembly of atom vacancies into quasi one-dimensional line structures and (b) quantum-driven assembly of atoms into atomically-smooth two-dimensional thin films. In the classical assembly phenomenon, adatom vacancies, created via elastic strain-relaxation in compressively strained atom chains on a silicon substrate, self-organize into meandering vacancy lines. The average spacing between these line defects can be varied by adjusting the chemical potential μ of the adsorbed atoms. We implemented a lattice model …

Development And Implementation Of A New Technique To Study (P,Α) Reactions Relevant To Nucleosynthesis In Binary Systems, Brian Hossain Moazen

Doctoral Dissertations

The accurate determination of the strengths and energies of resonances in (p,alpha) reactions is important for understanding the influence of reaction cycles to element synthesis in many astrophysical environments. Thus far, (p,alpha) studies in inverse kinematics have employed solid polypropylene targets. These are not always advantageous, especially when the energy loss of the incoming beam in the solid target is significantly larger than the resonance width. At the Holifield Radioactive Ion Beam Facility, a new technique has been developed for measuring the strengths and energies of (p,alpha) reactions. In this technique, a large differentially-pumped scattering chamber is filled with hydrogen …

Wide-Range Characterization Of Current Conduction In Superconductors-Tuning Their Properties By Nanoscale Modification Of Materials, Özgür Polat

Doctoral Dissertations

Significant progress has been made in the development of YBa₂Cu₃O_7-x (YBCO)-based coated conductors (CCs) since the discovery of YBCO in 1987. Nowadays, high temperature superconductor (HTS) materials are advancing toward wide application areas in medical physics, industry, and science. The successful applications of these materials require clear understanding of the mechanisms controlling the current carrying capacity. It has been demonstrated the maximum current that a HTS can support is strongly affected by the vortex dynamics within the HTS materials. In this dissertation, we employed a combination of methods: conventional transport, magnetometry in a swept magnetic …

Constructing A Magneto-Optical Trap For Cold Atom Trapping, Eric S. Muckley

Physics

A magneto-optical trap, or MOT, is a device that traps atoms between three pairs of opposing perpendicular laser beams for cooling the atoms to temperatures near absolute zero. The MOT uses Doppler cooling and a magnetic quadrupole field to trap the atoms; in our case, Rb87 atoms. In the future, the MOT will be used in experiments pertaining to the advancement of quantum computing. In this paper, I explain some of the processes required for construction and operation of the MOT.

Developing A B-Jet Tagging Algorithm For Alice: Lessons From Cdf, Paul Chester-John Carlson

Physics

This paper compares the detectors and algorithms developed and used at both A Large Ion Collider Experiment (ALICE) and the Collider Detector at Fermilab (CDF). We found that the detectors share many similarities in data collection and analysis methods and that by adapting algorithms that have been tested and used at CDF, ALICE could augment its existing algorithms. The algorithms formed from this adaptation will help ALICE isolate b-jets quickly and explore the quark-gluon plasma, ultimately expanding our understanding of the strong nuclear force and its role in the evolution of our universe.

Theoretical Study Of Localized Surface Plasmons Of Metal Nanoparticles, Clusters And Embedded Metal Nanoparticles In Matrices, Masoud Shabani Nezhad Navrood

Dissertations

Localized surface plasmons resonances (LSPRs) in metallic nanoparticles (NPs) arise from the interactions between incident light and conduction electrons and have attracted enormous research interest in recent years both for their fundamental nature as well as applications in interdisciplinary areas of sciences such as biological imaging, plasmonic photo-thermal therapy, photovoltaics, and plasmonic sensors. LSPRs are strongly localized and depend on the shape, size, the composition of the NPs, the polarization direction of the incident light, refractive index (RI) of the surrounding medium as well as on the chemical environment that surrounded NPs. Although significant research has progressed both theoretically and …

Atom Scattering From Metals, William Hayes

All Dissertations

In the initial portion of this dissertation studies of Ar
scattering from Ru(0001) at thermal and hyperthermal energies are
compared to calculations with classical scattering theory. These
data exhibited a number of characteristics that are unusual in
comparison to other systems for which atomic beam experiments have
been carried out under similar conditions. The measured energy
losses were unusually small. Some of the angular distributions
exhibited an anomalous shoulder feature in addition to a broad
peak near the specular direction and quantum mechanical
diffraction was observed under conditions for which it was not
expected. Many of the unusual features observed …

Light Beaming From A Single Subwavelength Metal Slit, Pengyu Chen

All Theses

In this thesis, light transmission through a single sub-wavelength slit in a silver thin film with periodic gratings at the exit side of the slit has been studied in both the visible and mid-infrared wavelength ranges.
In the visible wavelength range, we first investigate the enhancement of plasmonic light beaming efficiency by near field resonance in a subwavelength metallic slit-groove beaming structure. We show that by varying the film thickness and the separation distance of the beaming grating, the intensity of the near field can be greatly enhanced by resonance, which leads to the increase of the beaming efficiency. Moreover, …

Polarimetry Studies For The Npdgamma Experiment At The Sns, Mostafa Jon Dadras

Masters Theses

The NPDGamma collaboration aims to measure a parity{violating directional gamma-ray asymmetry from the capture of polarized cold neutrons on protons. The asymmetry, predicted to be on the order of 50 ppb, is a result of the weak interaction between mesons and nucleons during the neutron capture reaction. The experiment is designed to make a statistics limited measurement of the asymmetry at the level of about 20%. The experiment will be carried out at the Fundamental neutron Physics Beamline (FnPB) at the Spallation Neutron Source (SNS). The neutron beam is polarized by a super{mirror polarizer. A 9.5 G magnetic field guides …

Optical And Terahertz Energy Concentration On The Nanoscale In Plasmonics, Anastasia Rusina

Physics and Astronomy Dissertations

We introduce an approach to implement full coherent control on nanometer length scales. It is based on spatiotemporal modulation of the surface plasmon polariton (SPP) fields at the thick edge of a nanowedge. The SPP wavepackets propagating toward the sharp edge of this nanowedge are compressed and adiabatically concentrated at a nanofocus, forming an ultrashort pulse of local fields. The profile of the focused waveform as a function of time and one spatial dimension is completely coherently controlled. We establish the principal limits for the nanoconcentration of the terahertz (THz) radiation in metal/dielectric waveguides and determine their optimum shapes required …

Giant Plasmonic Energy And Momentum Transfer On The Nanoscale, Maxim Durach

Physics and Astronomy Dissertations

We have developed a general theory of the plasmonic enhancement of many-body phenomena resulting in a closed expression for the surface plasmon-dressed Coulomb interaction. It is shown that this interaction has a resonant nature. We have also demonstrated that renormalized interaction is a long-ranged interaction whose intensity is considerably increased compared to bare Coulomb interaction over the entire region near the plasmonic nanostructure. We illustrate this theory by re-deriving the mirror charge potential near a metal sphere as well as the quasistatic potential behind the so-called perfect lens at the surface plasmon (SP) frequency. The dressed interaction for an important …

Development And Comparison Of Methods For Measuring Directional Sound Arrivals In Rooms, Brian Trevor Thornock

Theses and Dissertations

In room acoustics, the directional information of sound arrivals at a listening location can be used to diagnose the origins of problematic reflections so offending surfaces or other features can be properly treated. It can also be used for other purposes, including the study of psychoacoustic indicators. Many methods have been developed in the past to derive directional information, but despite their benefits, each has had significant drawbacks that have necessitated further research into their properties and development of an improved method. This thesis presents a review of past methods, their benefits and shortcomings. It discusses many theoretical and practical …

Duty Cycle Maintenance In An Artificial Neuron, William Halbert Barnett

Physics and Astronomy Theses

Neuroprosthetics is at the intersection of neuroscience, biomedical engineering, and physics. A biocompatible neuroprosthesis contains artificial neurons exhibiting biophysically plausible dynamics. Hybrid systems analysis could be used to prototype such artificial neurons. Biohybrid systems are composed of artificial and living neurons coupled via real-time computing and dynamic clamp. Model neurons must be thoroughly tested before coupled with a living cell. We use bifurcation theory to identify hazardous regimes of activity that may compromise biocompatibility and to identify control strategies for regimes of activity desirable for functional behavior. We construct real-time artificial neurons for the analysis of hybrid systems and demonstrate …

Wrinkling, Folding, And Snapping Instabilities In Polymer Films, Douglas Peter Holmes

Open Access Dissertations

This work focuses on understanding deformation mechanisms and responsiveness associated with the wrinkling, folding, and snapping of thin polymer films. We demonstrated the use of elastic instabilities in confined regimes, such as the crumpling and snapping of surface attached sheets. We gained fundamental insight into a thin film's ability to localize strain. By taking advantage of geometric strain localization we were able to develop new strategies for responsive surfaces that will have a broad impact on adhesive, optical, and patterning applications. Using the rapid closure of the Venus flytrap's leafets as dictated by the onset of a snap instability as …

Contributing Efforts In The Search For Neutrinoless Double Beta Decay, Laura Christine Sparks

Physics

Cryogenic Underground Observatory for Rare Events (CUORE) will be part of the next generation of detectors used to search for neutrinoless double beta decay (0νββ). Located in Assergi, Italy at the Gran Sasso National Laboratory (LNGS), CUORE will be a large cryogenic bolometer composed of 988 tellurium dioxide (TeO2) detectors with a total mass of 750 kg, and will search for 0νββ in 130Te. As the experiment will monitor the extremely rare event of 0νββ, all factors contributing to background need to be minimized to effectively increase the sensitivity. I assisted the LNGS researchers over the summer of 2008 by …

High Resolution Solar Observations From First Principles To Applications, Angelo P. Verdoni

Dissertations

The expression "high-resolution observations" in Solar Physics refers to the spatial, temporal and spectral domains in their entirety. High-resolution observations of solar fine structure are a necessity to answer many of the intriguing questions related to solar activity. However, a researcher building instruments for high-resolution observations has to cope with the fact that these three domains often have diametrically opposed boundary conditions. Many factors have to be considered in the design of a successful instrument. Modern post-focus instruments are more closely linked with the solar telescopes that they serve than in past. In principle, the quest for high-resolution observations already …

Carbon Nanotube Electronic Structures As Anti-Corrosion Coatings, Sreeya Sreevatsa

Dissertations

A new concept of corrosion prevention is considered in this study. Diode-like and transistor-like structures have been fabricated and analyzed in the study of ionic flow through the resulting potential barriers. The structures were made of functionalized carbon nanotubes. Carbon nanotubes are known for many remarkable properties among which is being chemically inert. Taking advantage of this property, a study of corrosion of steel was undertaken.

In the first case study, successive layers of functionalized carbon nanotubes were deposited to form p-n junctions on steel substrates. It was demonstrated that the corrosion was indeed impeded by the potential barrier formed …

Probing The Complex Magnetic, Electronic And Structural Properties In Correlated Manganese Oxides, Peng Gao

Dissertations

Rare-earth Manganese Oxides (RMnO₃) exhibit two distinct structural phases: the orthorhombic structure and the hexagonal structure. The doped orthorhombic phase exhibits a metal to insulator transition, charge ordering and a strong response of electron transport properties to magnetic fields (colossal magneto-resistance). At low temperatures, this system may also exhibit a finite polarization which couples to external magnetic fields. The hexagonal phase is known to have a large spontaneous polarization at high temperatures which couples to the low temperature magnetic order. These materials are important from the basic point of view of understanding strong electronic correlations and …

Photoionization Of The Be Isoelectronic Sequence: Relativistic And Nonrelativistic R-Matrix Calculations, Wei-Chun Chu

Physics and Astronomy Dissertations

The photoionization of the beryllium-like isoelectronic series has been studied. The bound state wave functions of the target ions were built with CIV3 program. The relativistic Breit-Pauli R-matrix method was used to calculate the cross sections in the photon energy range between the ionization threshold and 1s24f7/2 threshold for each ion. For the total cross sections of Be, B+, C+2, N+3, and O+4, our results match experiment well. The comparison between the present work and other theoretical works are also discussed. We show the comparison with our LS results as it indicates the importance of relativistic effects on different ions. …

Scan-Based Near-Field Acoustical Holography On Partially Correlated Sources, Michael D. Gardner

Theses and Dissertations

Scan-based near-field acoustical holography (NAH) is applied to partially correlated sources. Partial field decomposition via the virtual coherence method is used to implement the scan-based NAH. The background and theory of these methods are developed. Multiple stationary reference microphones are required for the partial field decomposition. Guidelines for reference microphone placement in the literature thus far have been limited. Improved guidelines for reference microphones are given after the results of two sets of experiments. The first set involves discrete, partially correlated sources, both physical and numerical. The second set of experiments is strictly numerical and involves continuous sources. Fewer microphones …

Experimental Studies Of Exotic Negative Ions, Shaun Gerald Ard

Doctoral Dissertations

Although negative ions have been studied extensively for quite some time, their study continues to offer insight into developing and refining quantum chemical modeling techniques. Negative ion states remain difficult to treat ab initio due to the significant electron-electron correlation, thus putting a premium on experimental results to guide the way. Experimental techniques such as Electrospray Ionization (ESI) and Rydberg Electron Transfer (RET) have made study of some exotic negative ions in the gas phase possible for the first time. Multiply Charged Anions (MCAs) of several families of molecules were studied using Collision Induced Dissociation (CID) and Infrared Multi Photon …

Single Walled Carbon Nanotube Networks As Transparent Conductors, Matthew Patrick Garrett

Doctoral Dissertations

A variety of technological applications depend on transparent conducting films, and carbon nanotubes have the properties required to serve in that role. Single-walled carbon nanotube networks have been studied as transparent conductors in order to understand and optimize their electrical and optical properties. Nanotube films are complex networks of semiconducting and metallic nanotubes, bundled and branched in multifarious directions, with different strength connections between bundles. Chemical modification of nanotubes and inclusion of non-nanotube material can further alter network properties. Separating the contributions of all aspects of the network is a necessary but daunting task in order to optimize nanotube films. …