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Articles 1 - 12 of 12
Full-Text Articles in Physics
Evaluation Of Magnesium As A Hall Thruster Propellant, Mark A. Hopkins
Evaluation Of Magnesium As A Hall Thruster Propellant, Mark A. Hopkins
Dissertations, Master's Theses and Master's Reports - Open
In this study, the use of magnesium as a Hall thruster propellant was evaluated. A xenon Hall thruster was modified such that magnesium propellant could be loaded into the anode and use waste heat from the thruster discharge to drive the propellant vaporization. A control scheme was developed, which allowed for precise control of the mass flow rate while still using plasma heating as the main mechanism for evaporation. The thruster anode, which also served as the propellant reservoir, was designed such that the open area was too low for sufficient vapor flow at normal operating temperatures (i.e. plasma heating …
Barium Concentrations In Rock Salt By Laser Induced Breakdown Spectroscopy, Kiley J. Spirito
Barium Concentrations In Rock Salt By Laser Induced Breakdown Spectroscopy, Kiley J. Spirito
Dissertations, Master's Theses and Master's Reports - Open
Time-REsolved Laser Induced Breakdown Spectroscopy (TRELIBS) was used to determine the elemental concentration of barium in Texas Dome rock salt. TRELIBS allows for an efficient and in situ concentration analysis technique that detects a wide range of elements with no sample preparation.
TRELIBS measurements were made in the 545nm to 594nm wavelength range. The proximity of a strong barium emission line (553.5481 nm) to the sodium doublet (588.9950 nm and 589.5924 nm) allowed for measurement within a single frame of the spectrograph.
This barium emission line was compared to the sodium doublet for relative intensity. A homemade calibration sample containing …
Multiscale Examination And Modeling Of Electron Transport In Nanoscale Materials And Devices, Douglas R. Banyai
Multiscale Examination And Modeling Of Electron Transport In Nanoscale Materials And Devices, Douglas R. Banyai
Dissertations, Master's Theses and Master's Reports - Open
For half a century the integrated circuits (ICs) that make up the heart of electronic devices have been steadily improving by shrinking at an exponential rate. However, as the current crop of ICs get smaller and the insulating layers involved become thinner, electrons leak through due to quantum mechanical tunneling. This is one of several issues which will bring an end to this incredible streak of exponential improvement of this type of transistor device, after which future improvements will have to come from employing fundamentally different transistor architecture rather than fine tuning and miniaturizing the metal-oxide-semiconductor field effect transistors (MOSFETs) …
Understanding Electronic Structure And Transport Properties In Nanoscale Junctions, Kamal B. Dhungana
Understanding Electronic Structure And Transport Properties In Nanoscale Junctions, Kamal B. Dhungana
Dissertations, Master's Theses and Master's Reports - Open
Understanding the electronic structure and the transport properties of nanoscale materials are pivotal for designing future nano-scale electronic devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular electronics has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder …
Study Of Non-Reciprocal Dichroism In Photonic Structures, Anindya Majumdar
Study Of Non-Reciprocal Dichroism In Photonic Structures, Anindya Majumdar
Dissertations, Master's Theses and Master's Reports - Open
Non-reciprocal phenomena are widely used in photonic devices. Important applications such as isolators and circulator waveguide structures depend on non-reciprocal effects. The basis of these phenomena is a difference in phase or refractive index for an electromagnetic wave of a given polarization as it travels through a medium in opposite directions. Generally this applies to the real part of the refractive index. The present report addresses a less studied phenomenon in non-reciprocal propagation, namely differences in optical absorption loss for a given polarization state in opposite propagation directions, a phenomenon we have termed non-reciprocal dichroism. Nonreciprocal dichroism can be defined …
Multi-Mode And Single Mode Polymer Waveguides And Structures For Short-Haul Optical Interconnects, Kevin L. Kruse
Multi-Mode And Single Mode Polymer Waveguides And Structures For Short-Haul Optical Interconnects, Kevin L. Kruse
Dissertations, Master's Theses and Master's Reports - Open
Single mode and multi-mode polymer optical waveguides are a viable solution for replacing copper interconnects as high speed and large bandwidth short-haul optical interconnects in next-generation supercomputers and data servers. A precision laser direct writing method is implemented for producing various single mode and multi-mode polymer waveguide structures and their performance is evaluated experimentally showing agreement with theoretically developed models. The laser direct writing method is the optimal solution for low-rate cost-effective prototyping and large area panel production.
A single mode polymer waveguide bridge module for silicon to glass optical fibers is designed, modeled, fabricated, and measured. The bridge module …
Modeling And Simulation Of Microstructures, Mechanisms, And Diffraction Effects In Energy Materials: Ferroelectrics And Lithium Ion Battery Cathode Materials, Jie Zhou
Dissertations, Master's Theses and Master's Reports - Open
Ferroelectric materials, as a large family exploited for the application of sensors, transducers and random access memories, open up a remarkable ground both for fundamental science and industry. Dielectric and piezoelectric properties are of the most interest in ferroelectric materials, which motivate research to enhance ferroelectric properties based on various application purposes. Among the multitudinous candidates in ferroelectric family, pseudo binary solid solutions with ABO3 lattice structure attract special attention in virtue of their large strain response when applying external loading. Furthermore, existence of morphological phase boundary (MPB) on their phase diagrams shed light on tuning material compositions to …
Geometry Induced Magneto-Optic Effects In Lpe Grown Magnetic Garnet Films, Ashim Chakravarty
Geometry Induced Magneto-Optic Effects In Lpe Grown Magnetic Garnet Films, Ashim Chakravarty
Dissertations, Master's Theses and Master's Reports - Open
This dissertation addresses dimensionality-induced magneto-optic effects in liquid-phaseepitaxy magnetic garnet thin films. It is found that the Faraday rotation (FR) per unit length evinces a marked and steady enhancement as the film thickness is reduced below ~100 nm in Bi0.8Gd0.2Lu2Fe5O12, although it remains constant in the micron- and most of the submicron- regime. The reported specific FR change in such reduced dimensions is due to sizedependent modifications in diamagnetic transition processes in the garnet film. These processes correspond to the electronic transitions from the singlet 6S ground state to …
Structures, Properties And Functionalities Of Magnetic Domain Walls In Thin Films, Nanowires And Atomic Chains: Micromagnetic And Ab Initio Studies, Liwei D. Geng
Dissertations, Master's Theses and Master's Reports - Open
Structures, properties and functionalities of magnetic domain walls in thin film, nanowires and atomic chains are studied by micromagnetic simulations and ab initio calculations in this dissertation. For magnetic domain walls in thin films, we computationally investigated the dynamics of one-dimensional domain wall line in ultrathin ferromagnetic film, and the exponent α = 1.24 ± 0.05 is obtained in the creep regime near depinning force, indicating the washboard potential model is supported by our simulations. Furthermore, the roughness, creep, depinning and flow of domain wall line with commonly existed substructures driven by magnetic field are also studied. Our simulation results …
A Method For Determining The Mass Composition Of Ultra-High Energy Cosmic Rays By Predicting The Depth Of First Interaction Of Individual Extensive Air Showers, Tolga Yapici
Dissertations, Master's Theses and Master's Reports - Open
Particle accelerators have been used to characterize the properties of particle and subatomic particles. The most advanced particle accelerators built, LHC, can run at 1017 eV. It is not possible with current technology to accelerate particle to the energies that can be detected by cosmic ray observatories.
In the past, by the direct measurements of cosmic rays, scientists discovered sub-atomic particles. Being accelerated to energies higher than 1018 eV, cosmic rays carry important information for particle physics. We have developed a method, which is a combination of Artificial Neural Networks and simple algebraic method that uses parameters from the extensive …
Search For Tev Gamma-Ray Sources In The Galactic Plane With The Hawc Observatory, Hao Zhou
Search For Tev Gamma-Ray Sources In The Galactic Plane With The Hawc Observatory, Hao Zhou
Dissertations, Master's Theses and Master's Reports
Cosmic rays, with an energy density of $\sim1\,\text{eV}\,\text{cm}^{-3}$, play an important role in the evolution of our Galaxy. Very high energy (TeV) gamma rays provide unique information about the acceleration sites of Galactic cosmic rays. The High Altitude Water Cherenkov (HAWC) Gamma-Ray Observatory is an all-sky surveying instrument sensitive to gamma rays from 100\:GeV to 100\:TeV with a 2\,steradian instantaneous field of view and a duty cycle of $>95\%$. The array is located in Sierra Negra, Mexico at an elevation of 4,100\,m and was inaugurated in March 2015. Thanks to its modular design, science operation began in Summer 2013 …
Relativistic Configuration Interaction Calculations Of The Atomic Properties Of Selected Transition Metal Positive Ions; Ni Ii, V Ii And W Ii, Marwa Hefny Abdalmoneam
Relativistic Configuration Interaction Calculations Of The Atomic Properties Of Selected Transition Metal Positive Ions; Ni Ii, V Ii And W Ii, Marwa Hefny Abdalmoneam
Dissertations, Master's Theses and Master's Reports
Relativistic Configuration Interaction (RCI) method has been used to investigate atomic properties of the singly ionized transition metals including Nickel (Ni II), Vanadium (V II), and Tungsten (W II). The methodology of RCI computations was also improved. Specifically, the method to shift the energy diagonal matrix of the reference configurations was modified which facilitated including the effects of many electronic configurations that used to be difficult to be included in the energy matrix and speeded-up the final calculations of the bound and continuum energy spectrum. RCI results were obtained for three different cases:
- Atomic moments and polarizabilities of Ni II; …