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Articles 1 - 19 of 19
Full-Text Articles in Physical Sciences and Mathematics
Advanced Iii-V / Si Nano-Scale Transistors And Contacts: Modeling And Analysis, Seung Hyun Park
Advanced Iii-V / Si Nano-Scale Transistors And Contacts: Modeling And Analysis, Seung Hyun Park
Open Access Dissertations
The exponential miniaturization of Si CMOS technology has been a key to the electronics revolution. However, the continuous downscaling of the gate length becomes the biggest challenge to maintain higher speed, lower power, and better electrostatic integrity for each following generation. Hence, novel devices and better channel materials than Si are considered to improve the metal-oxide-semiconductor field-effect transistors (MOSFETs) device performance. III-V compound semiconductors and multi-gate structures are being considered as promising candidates in the next CMOS technology. III-V and Si nano-scale transistors in different architectures are investigated (1) to compare the performance between InGaAs of III-V compound semiconductors and …
Structural Characterization Of Multimetallic Nanoparticles, Vineetha Mukundan
Structural Characterization Of Multimetallic Nanoparticles, Vineetha Mukundan
Open Access Dissertations
Bimetallic and trimetallic alloy nanoparticles have enhanced catalytic activities due to their unique structural properties. Using in situ time-resolved synchrotron based x-ray diffraction, we investigated the structural properties of nanoscale catalysts undergoing various heat treatments. Thermal treatment brings about changes in particle size, morphology, dispersion of metals on support, alloying, surface electronic properties, etc. First, the mechanisms of coalescence and grain growth in PtNiCo nanoparticles supported on planar silica on silicon were examined in detail in the temperature range 400-900°C. The sintering process in PtNiCo nanoparticles was found to be accompanied by lattice contraction and L10chemical ordering. …
A New Passive Surface Water Flux Meter For Simultaneous Measurement Of Contaminant And Water Fluxes In Streams And Rivers, Stephen A. Sassman
A New Passive Surface Water Flux Meter For Simultaneous Measurement Of Contaminant And Water Fluxes In Streams And Rivers, Stephen A. Sassman
Open Access Dissertations
A passive surface water flux meter (PSFM) for measurement of contaminant concentration/flux in rivers and streams is described and tested. The novel PSFM design was developed for portability and ease of adaptability for a variety of contaminant classes. Although previous designs have been evaluated under constant flow conditions, the PSFM has never been used for measurement of pesticides or hormones and this is the first time that it has been tested under transient flow. Discharge through the PSFM is assessed by measuring miscible displacement of alcohol tracers from granular activated carbon (GAC). The tracer retardation factors (R) measured by miscible …
Digital Provenance - Models, Systems, And Applications, Salmin Sultana
Digital Provenance - Models, Systems, And Applications, Salmin Sultana
Open Access Dissertations
Data provenance refers to the history of creation and manipulation of a data object and is being widely used in various application domains including scientific experiments, grid computing, file and storage system, streaming data etc. However, existing provenance systems operate at a single layer of abstraction (workflow/process/OS) at which they record and store provenance whereas the provenance captured from different layers provide the highest benefit when integrated through a unified provenance framework. To build such a framework, a comprehensive provenance model able to represent the provenance of data objects with various semantics and granularity is the first step. In this …
Image Analysis Using Visual Saliency With Applications In Hazmat Sign Detection And Recognition, Bin Zhao
Image Analysis Using Visual Saliency With Applications In Hazmat Sign Detection And Recognition, Bin Zhao
Open Access Dissertations
Visual saliency is the perceptual process that makes attractive objects "stand out" from their surroundings in the low-level human visual system. Visual saliency has been modeled as a preprocessing step of the human visual system for selecting the important visual information from a scene. We investigate bottom-up visual saliency using spectral analysis approaches. We present separate and composite model families that generalize existing frequency domain visual saliency models. We propose several frequency domain visual saliency models to generate saliency maps using new spectrum processing methods and an entropy-based saliency map selection approach. A group of saliency map candidates are then …
Tunable Impedance Matching Network Fundamental Limits And Pracitical Considerations, Wesley N. Allen
Tunable Impedance Matching Network Fundamental Limits And Pracitical Considerations, Wesley N. Allen
Open Access Dissertations
As wireless devices continue to increase in utility while decreasing in dimension, design of the RF front-end becomes more complex. It is common for a single handheld device to operate on a plethora of frequency bands, utilize multiple antennae, and be subjected to a variety of environments. One complexity in particular which arises from these factors is that of impedance mismatch. Recently, tunable impedance matching networks have begun to be implemented to address this problem. ^ This dissertation presents the first in-depth study on the frequency tuning range of tunable impedance matching networks. Both the fundamental limitations of ideal networks …
Effects Of Energetic Irradiation On Materials And Devices Based On Graphene And Topological Insulators, Isaac Childres
Effects Of Energetic Irradiation On Materials And Devices Based On Graphene And Topological Insulators, Isaac Childres
Open Access Dissertations
This report focuses on the optical and electronic properties of graphene and topological insulators and how these Dirac fermion systems interact with energetic irradiation. We first present data exploring the effects of electron-beam and oxygen plasma induced disorder on the electronic properties and Raman spectra of graphene. These initial investigations were important for relating Raman peak intensities and weak localization features to each other and to an average disorder length in graphene, LD. ^ We then integrate gate-effect measurements into the Raman spectroscopy study to fully explore the relationships between carrier density, disorder and Raman spectrum signatures. We …
Irrigation With Treated Wastewater: Potential And Limitations, Anne Dare
Irrigation With Treated Wastewater: Potential And Limitations, Anne Dare
Open Access Dissertations
As the world population increases and resources become more coveted, water emerges as a key component to global food security. The Middle East and North Africa (MENA) is among the driest regions in the world: containing just one percent of the world's freshwater resources. An increasing population creates greater quantities of wastewater and demands greater quantities of food, so an obvious connection arises. However logical wastewater reuse may be for bridging the irrigation supply-demand gap in this arid region, significant limitations prevent widespread adoption. The overall goal of this research is to take a holistic view of the limitations facing …
Probabilistic Uncertainty Quantification And Experiment Design For Nonlinear Models: Applications In Systems Biology, Vu Cao Duy Thien Dinh
Probabilistic Uncertainty Quantification And Experiment Design For Nonlinear Models: Applications In Systems Biology, Vu Cao Duy Thien Dinh
Open Access Dissertations
Despite the ever-increasing interest in understanding biology at the system level, there are several factors that hinder studies and analyses of biological systems. First, unlike systems from other applied fields whose parameters can be effectively identified, biological systems are usually unidentifiable, even in the ideal case when all possible system outputs are known with high accuracy. Second, the presence of multivariate bifurcations often leads the system to behaviors that are completely different in nature. In such cases, system outputs (as function of parameters/inputs) are usually discontinuous or have sharp transitions across domains with different behaviors. Finally, models from systems biology …
Dynamic Control Of Plasmonic Resonances With Graphene Based Nanostructures, Naresh Kumar Emani
Dynamic Control Of Plasmonic Resonances With Graphene Based Nanostructures, Naresh Kumar Emani
Open Access Dissertations
Light incident on a metallic structure excites collective oscillations of electrons termed as plasmons. These plasmons are useful in control and manipulation of information in nanoscale dimensions and at high operating frequencies. Hence, the field of plasmonics opens up the possibility of developing nanoscale optoelectronic circuitry for computing and sensing applications. One of the challenges in this effort is the lack of tunable plasmonic resonance. Currently, the resonant wavelength of plasmonic structure is fixed by the material and structural parameters. Post-fabrication dynamic control of a plasmonic resonance is rather limited.^ In this thesis we explore the combination of optoelectrical properties …
Functional Programming Abstractions For Weakly Consistent Systems, Sivaramakrishnan Krishnamoorthy Chandrasekaran
Functional Programming Abstractions For Weakly Consistent Systems, Sivaramakrishnan Krishnamoorthy Chandrasekaran
Open Access Dissertations
In recent years, there has been a wide-spread adoption of both multicore and cloud computing. Traditionally, concurrent programmers have relied on the underlying system providing strong memory consistency, where there is a semblance of concurrent tasks operating over a shared global address space. However, providing scalable strong consistency guarantees as the scale of the system grows is an increasingly difficult endeavor. In a multicore setting, the increasing complexity and the lack of scalability of hardware mechanisms such as cache coherence deters scalable strong consistency. In geo-distributed compute clouds, the availability concerns in the presence of partial failures prohibit strong consistency. …
Applications Of Femtosecond Coherent Anti-Stokes Raman Scattering In Combustion, Claresta Nicole Dennis
Applications Of Femtosecond Coherent Anti-Stokes Raman Scattering In Combustion, Claresta Nicole Dennis
Open Access Dissertations
The dissertation deals with the further development of chirped-probe-pulse femtosecond coherent anti-Stokes Raman spectroscopy (CPP fs-CARS) for applications of gas phase thermometry and extension to methane concentration measurements. The main effort has been to assess the usefulness and robustness of the technique in turbulent combustors of practical interest. A primary aim has been to evaluate the use of CPP fs-CARS for vibrational N2 thermometry in a highly turbulent environment. It has been suggested that due to the laser beam temporal overlap required for fs-CARS signal generation, the technique would be unsuccessful due to beam propagation retardation effects from density …
Usability Of Immersive Virtual Reality Input Devices, Christopher G. Mankey
Usability Of Immersive Virtual Reality Input Devices, Christopher G. Mankey
Open Access Dissertations
This research conducts a usability analysis of human interface devices within an Immersive Virtual Reality Environment. The analysis is carried out for two different interface devices, a commercially available Intersense © Wand and a home built pinch glove and wireless receiver. Users were asked to carry out a series of minor tasks involving placement of shaped blocks into corresponding holes within an Immersive Virtual Reality Environment. Performance was evaluated in terms of speed, accuracy and precision via the collection of completion times, errors made and the precision of motion during the experiment.
Theory Of Topological Insulators And Its Applications, Parijat Sengupta
Theory Of Topological Insulators And Its Applications, Parijat Sengupta
Open Access Dissertations
An important pursuit in semiconductor physics is to discover new materials to sustain the continuous progress and improvements in the current electronic devices. Traditionally, three material types are in use: 1) Metals 2) Semiconductors 3) Insulators. All the three material types are classified according to the energy gap between conduction and valence bands derived from band theory of solids. Recent theoretical predictions and confirmed by experimental observations have provided evidence that there exists materials which behave as insulators in the bulk but possess gapless conducting states on the surface. These new class of materials are called topological insulators (TI). In …
Optical Spectroscopy And Langmuir Probe Diagnostics Of Microwave Plasma In Synthesis Of Graphene-Based Nanomaterials, Alfredo D. Tuesta
Optical Spectroscopy And Langmuir Probe Diagnostics Of Microwave Plasma In Synthesis Of Graphene-Based Nanomaterials, Alfredo D. Tuesta
Open Access Dissertations
Along with the revolutionary discovery and development of carbon nanostructures, such as carbon nanotubes and graphitic sheets, has arrived the potential for their application in the fields of medicine, bioscience and engineering due to their exceptional structural, thermal and electrical properties. As roll-to-roll plasma deposition systems begin to provide means for large scale production of these nanodevices, a detailed understanding of the environment responsible for their synthesis is imperative in order to more accurately design and control the growth of carbon nanodevices. To date, the understanding of the chemistry and kinetics that govern the synthesis of carbon nanodevices is only …
Algebraic Level Sets For Cad/Cae Integration And Moving Boundary Problems, Kritika Upreti
Algebraic Level Sets For Cad/Cae Integration And Moving Boundary Problems, Kritika Upreti
Open Access Dissertations
Boundary representation (B-rep) of CAD models obtained from solid modeling kernels are commonly used in design, and analysis applications outside the CAD systems. Boolean operations between interacting B-rep CAD models as well as analysis of such multi-body systems are fundamental operations on B-rep geometries in CAD/CAE applications. However, the boundary representation of B-rep solids is, in general, not a suitable representation for analysis operations which lead to CAD/CAE integration challenges due to the need for conversion from B-rep to volumetric approximations. The major challenges include intermediate mesh generation step, capturing CAD features and associated behavior exactly and recurring point containment …
Hydrogen Loading System Development And Evaluation Of Tritiated Substrates To Optimize Performance In Tritium Based Betavoltaics, Thomas E. Adams
Hydrogen Loading System Development And Evaluation Of Tritiated Substrates To Optimize Performance In Tritium Based Betavoltaics, Thomas E. Adams
Open Access Dissertations
State-of-the-art hydrogen loading system onto thin metallic films based on differential pressure in calibrated chambers has been developed for conditions pressures and temperatures up to 69 bar and 500°C, respectively. Experiments on hydrogen loading on to palladium films of thickness 50 and 250 nm were conducted at pressure ranging from 0.2 bar to 10 bar at temperature 310°C. For first time film hydrogen loading was carried out at 1 bar and at room temperature which temperature. Beta flux exiting surface of metal tritide films has been modeled with MC-SET (Monte Carlo Simulation of Electron Trajectories in solids). Surface beta flux …
Energy Efficient Hybrid Computing Systems Using Spin Devices, Mrigank Sharad
Energy Efficient Hybrid Computing Systems Using Spin Devices, Mrigank Sharad
Open Access Dissertations
Emerging spin-devices like magnetic tunnel junctions (MTJ's), spin-valves and domain wall magnets (DWM) have opened new avenues for spin-based logic design. This work explored potential computing applications which can exploit such devices for higher energy-efficiency and performance. The proposed applications involve hybrid design schemes, where charge-based devices supplement the spin-devices, to gain large benefits at the system level. As an example, lateral spin valves (LSV) involve switching of nanomagnets using spin-polarized current injection through a metallic channel such as Cu. Such spin-torque based devices possess several interesting properties that can be exploited for ultra-low power computation. Analog characteristic of spin …
Fundamental Studies On Copper Zeolites For Catalytic No X Abatement, Anuj Arun Verma
Fundamental Studies On Copper Zeolites For Catalytic No X Abatement, Anuj Arun Verma
Open Access Dissertations
Stringent regulations in mobile NOx emissions have resulted in the development of Standard Selective Catalytic Reduction (SCR) as the dominant NOx abatement technology in lean burn diesel engines. Standard SCR is a reaction of nitric oxide (NO) with ammonia (NH3), in the presence of oxygen (O 2) to form nitrogen (N2) and water (H2O). Copper containing zeolites show commercially viable SCR performance. Cu-SSZ-13 (CHA framework), a member of this family, is a preferred catalyst for SCR applications because it shows exceptional hydrothermal stability in addition to commercially viable SCR performance. Our work focuses …