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Two-photon Photoemission of Organic Semiconductor Molecules on Ag(111)

Description: Angle- and time-resolved two-photon photoemission (2PPE) was used to study systems of organic semiconductors on Ag(111). The 2PPE studies focused on electronic behavior specific to interfaces and ultrathin films. Electron time dynamics and band dispersions were characterized for ultrathin films of a prototypical n-type planar aromatic hydrocarbon, PTCDA, and representatives from a family of p-type oligothiophenes.In PTCDA, electronic behavior was correlated with film morphology and growth modes… more
Date: May 15, 2008
Creator: Yang, Aram & Yang, Aram
Partner: UNT Libraries Government Documents Department
open access

Nanocrystal Solar Cells

Description: This dissertation presents the results of a research agenda aimed at improving integration and stability in nanocrystal-based solar cells through advances in active materials and device architectures. The introduction of 3-dimensional nanocrystals illustrates the potential for improving transport and percolation in hybrid solar cells and enables novel fabrication methods for optimizing integration in these systems. Fabricating cells by sequential deposition allows for solution-based assembly of… more
Date: December 15, 2006
Creator: Gur, Ilan
Partner: UNT Libraries Government Documents Department
open access

Development and Integration of Hardware and Software for Active-Sensors in Structural Monitoring

Description: Structural Health Monitoring (SHM) promises to deliver great benefits to many industries. Primarily among them is a potential for large cost savings in maintenance of complex structures such as aircraft and civil infrastructure. However, several large obstacles remain before widespread use on structures can be accomplished. The development of three components would address many of these obstacles: a robust sensor validation procedure, a low-cost active-sensing hardware and an integrated softwar… more
Date: October 15, 2007
Creator: Overly, Timothy G.S.
Partner: UNT Libraries Government Documents Department
open access

Implementation of an interactive matching scheme for the Kapchinskij-Vladimirskij equations in the WARP code

Description: The WARP code is a robust electrostatic particle-in-cell simulation package used to model charged particle beams with strong space-charge forces. A fundamental operation associated with seeding detailed simulations of a beam transport channel is to generate initial conditions where the beam distribution is matched to the structure of a periodic focusing lattice. This is done by solving for periodic, matched solutions to a coupled set of ODEs called the Kapchinskij-Vladimirskij (KV) envelope equ… more
Date: April 15, 2008
Creator: Chilton, Sven H.
Partner: UNT Libraries Government Documents Department
open access

Monodisperse Platinum and Rhodium Nanoparticles as Model Heterogeneous Catalysts

Description: Model heterogeneous catalysts have been synthesized and studied to better understand how the surface structure of noble metal nanoparticles affects catalytic performance. In this project, monodisperse rhodium and platinum nanoparticles of controlled size and shape have been synthesized by solution phase polyol reduction, stabilized by polyvinylpyrrolidone (PVP). Model catalysts have been developed using these nanoparticles by two methods: synthesis of mesoporous silica (SBA-15) in the presence … more
Date: August 15, 2008
Creator: Coble, Inger M
Partner: UNT Libraries Government Documents Department
open access

Nanostructured Solid Oxide Fuel Cell Electrodes

Description: The ability of Solid Oxide Fuel Cells (SOFC) to directly and efficiently convert the chemical energy in hydrocarbon fuels to electricity places the technology in a unique and exciting position to play a significant role in the clean energy revolution. In order to make SOFC technology cost competitive with existing technologies, the operating temperatures have been decreased to the range where costly ceramic components may be substituted with inexpensive metal components within the cell and stac… more
Date: December 15, 2007
Creator: Sholklapper, Tal Zvi
Partner: UNT Libraries Government Documents Department
open access

Fabrication and characterization of submicron polymer waveguides by micro-transfer molding

Description: Various methods exist for fabrication of micron and submicron sized waveguide structures. However, most of them include expensive and time consuming semiconductor fabrication techniques. An economical method for fabricating waveguide structures is introduced and demonstrated in this thesis. This method is established based on previously well-developed photonic crystal fabrication method called two-polymer microtransfer molding. The waveguide in this work functions by a coupler structure that di… more
Date: December 15, 2009
Creator: Wu, Te-Wei
Partner: UNT Libraries Government Documents Department
open access

Magneto-optical study of the intermediate state in type-I superconductors: Effects of sample shape and applied current

Description: The magnetic flux structures in the intermediate state of bulk, pinning-free Type-I superconductors are studied using a high resolution magneto-optical imaging technique. Unlike most previous studies, this work focuses on the pattern formation of the coexisting normal and superconducting phases in the intermediate state. The influence of various parameters such as sample shape, structure defects (pinning) and applied current are discussed in relation to two distinct topologies: flux tubes (clos… more
Date: August 15, 2008
Creator: Hoberg, Jacob
Partner: UNT Libraries Government Documents Department
open access

Laser desorption/ionization mass spectrometry for direct profiling and imaging of small molecules from raw biological materials

Description: Matrix-assisted laser desorption/ionization(MALDI) mass spectrometry(MS) has been widely used for analysis of biological molecules, especially macromolecules such as proteins. However, MALDI MS has a problem in small molecule (less than 1 kDa) analysis because of the signal saturation by organic matrixes in the low mass region. In imaging MS (IMS), inhomogeneous surface formation due to the co-crystallization process by organic MALDI matrixes limits the spatial resolution of the mass spectral i… more
Date: May 15, 2008
Creator: Cha, Sangwon
Partner: UNT Libraries Government Documents Department
open access

Ion distributions at charged aqueous surfaces: Synchrotron X-ray scattering studies

Description: Surface sensitive synchrotron X-ray scattering studies were performed to obtain the distribution of monovalent ions next to a highly charged interface at room temperature. To control surface charge density, lipids, dihexadecyl hydrogen-phosphate (DHDP) and dimysteroyl phosphatidic acid (DMPA), were spread as monolayer materials at the air/water interface, containing CsI at various concentrations. Five decades in bulk concentrations (CsI) are investigated, demonstrating that the interfacial dist… more
Date: August 15, 2009
Creator: Bu, Wei
Partner: UNT Libraries Government Documents Department
open access

Development of a Progeny Marker for Steelhead; A Thesis submitted to Oregon State University.

Description: This study was undertaken to determine if strontium chloride could be used to create a trans-generational otolith mark in steelhead (Oncorhynchus mykiss). I completed two strontium injection trials and a survey of juvenile steelhead from various steelhead hatcheries. The two trials measured Sr:Ca ratios in otoliths in response to injections and the survey measured the natural variation in Sr:Ca ratios in otoliths of juvenile hatchery steelhead in response to the natural variation. In 2003, adul… more
Date: April 15, 2009
Creator: Shippentower, Gene E.
Partner: UNT Libraries Government Documents Department
open access

The Study and Implementation of Electrically Small Printed Antennas for an Integrated Transceiver Design

Description: This work focuses on the design and evaluation of the inverted-F, meandering-monopole, and loop antenna geometries. These printed antennas are studied with the goal of identifying which is suitable for use in a miniaturized transceiver design and which has the ability to provide superior performance using minimal Printed Circuit Board (PCB) space. As a result, the main objective is to characterize tradeoffs and identify which antenna provides the best compromise among volume, bandwidth and effi… more
Date: April 15, 2009
Creator: Speer, Pete
Partner: UNT Libraries Government Documents Department
open access

Integration of ab-initio nuclear calculation with derivative free optimization technique

Description: Optimization techniques are finding their inroads into the field of nuclear physics calculations where the objective functions are very complex and computationally intensive. A vast space of parameters needs searching to obtain a good match between theoretical (computed) and experimental observables, such as energy levels and spectra. Manual calculation defies the scope of such complex calculation and are prone to error at the same time. This body of work attempts to formulate a design and impl… more
Date: December 15, 2008
Creator: Sharda, Anurag
Partner: UNT Libraries Government Documents Department
open access

Applications of a single-molecule detection in early disease diagnosis and enzymatic reaction study

Description: Various single-molecule techniques were utilized for ultra-sensitive early diagnosis of viral DNA and antigen and basic mechanism study of enzymatic reactions. DNA of human papilloma virus (HPV) served as the screening target in a flow system. Alexa Fluor 532 (AF532) labeled single-stranded DNA probes were hybridized to the target HPV-16 DNA in solution. The individual hybridized molecules were imaged with an intensified charge-coupled device (ICCD) in two ways. In the single-color mode, target… more
Date: October 15, 2008
Creator: Li, Jiangwei
Partner: UNT Libraries Government Documents Department
open access

Structural Diagnostics of CFRP Composite Aircraft Components by Ultrasonic Guided Waves and Built-In Piezoelectric Transducers

Description: To monitor in-flight damage and reduce life-cycle costs associated with CFRP composite aircraft, an autonomous built-in structural health monitoring (SHM) system is preferred over conventional maintenance routines and schedules. This thesis investigates the use of ultrasonic guided waves and piezoelectric transducers for the identification and localization of damage/defects occurring within critical components of CFRP composite aircraft wings, mainly the wing skin-to-spar joints. The guided wav… more
Date: February 15, 2007
Creator: Matt, Howard M.
Partner: UNT Libraries Government Documents Department
open access

Under-sampling in a Multiple-Channel Laser Vibrometry System

Description: Laser vibrometry is a technique used to detect vibrations on objects using the interference of coherent light with itself. Most vibrometry systems process only one target location at a time, but processing multiple locations simultaneously provides improved detection capabilities. Traditional laser vibrometry systems employ oversampling to sample the incoming modulated-light signal, however as the number of channels increases in these systems, certain issues arise such a higher computational co… more
Date: August 15, 2006
Creator: Corey, J
Partner: UNT Libraries Government Documents Department
open access

Determining Application Runtimes Using Queueing Network Modeling

Description: Determination of application times-to-solution for large-scale clustered computers continues to be a difficult problem in high-end computing, which will only become more challenging as multi-core consumer machines become more prevalent in the market. Both researchers and consumers of these multi-core systems desire reasonable estimates of how long their programs will take to run (time-to-solution, or TTS), and how many resources will be consumed in the execution. Currently there are few methods… more
Date: March 15, 2007
Creator: Elliott, M
Partner: UNT Libraries Government Documents Department
open access

Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

Description: Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current disser… more
Date: October 15, 2008
Creator: Kalay, Yunus Eren
Partner: UNT Libraries Government Documents Department
open access

Dynamic magnetic susceptibility of systems with long-range magnetic order

Description: The utility of the TDR as an instrument in the study of magnetically ordered materials has been expanded beyond the simple demonstration purposes. Results of static applied magnetic field dependent measurements of the dynamic magnetic susceptibility, ?, of various ferromagnetic (FM) and antiferromagnetic (AFM) materials showing a range of transition temperatures (1-800 K) are presented. Data was collected primarily with a tunnel diode resonator (TDR) at different radio-frequencies ({approx}10-3… more
Date: May 15, 2009
Creator: Vannette, Matthew Dano
Partner: UNT Libraries Government Documents Department
open access

Nitrogen doped zinc oxide thin film

Description: To summarize, polycrystalline ZnO thin films were grown by reactive sputtering. Nitrogen was introduced into the films by reactive sputtering in an NO{sub 2} plasma or by N{sup +} implantation. All ZnO films grown show n-type conductivity. In unintentionally doped ZnO films, the n-type conductivities are attributed to Zn{sub i}, a native shallow donor. In NO{sub 2}-grown ZnO films, the n-type conductivity is attributed to (N{sub 2}){sub O}, a shallow double donor. In NO{sub 2}-grown ZnO films, … more
Date: December 15, 2003
Creator: Li, Sonny X.
Partner: UNT Libraries Government Documents Department
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