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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
81

Sustainable energy in military base design & layout

Campbell, Ira lee 27 May 2016 (has links)
The purpose of this study is to exlpore the possibilities of power generation using human and mechanical means. This paper will introduce alternative means, methods, and procedures for the implementation of cutting edge technologies to address the energy needs for today and the future. Further, this project will serve as an aid in the development of a base camp facility layout optimization system by understanding the proximity relationships between base camp components, developing a facility layout domain, and comparing generated layouts to existing models and camps.
82

Spontaneous simple and fractal pattern formation in nonlinear optical cavities

Bostock, C. January 2015 (has links)
The seminal work published by Alan Turing in 1952 provides the framework for our understanding of spontaneous pattern emergence in Nature. He proposed that when a reaction-diffusion system’s uniform states become sufficiently stressed, arbitrarily-small disturbances combined with inherent feedback processes can lead to spontaneous self-organization into finite-amplitude patterns with a single dominant scalelength. In this thesis, Turing’s universal mechanism is applied to a range of distinct nonlinear optical cavities. Of principal interest is a Fabry-Pérot (FP) resonator, which comprises a thin slice of diffusive Kerr-type material placed between two partially reflecting mirrors and pumped by an external plane wave. This model is a non-trivial generalization of the single-feedback mirror system, with the inclusion of the second mirror facilitating a disproportionate increase in complexity: here, the interplay between diffraction, counterpropagation and diffusive nonlinearity must be supplemented by more involved boundary conditions accommodating periodic pumping, mirror losses, interferomic mistuning, and time delays. The presented research analyzes the thin-slice FP cavity mathematically and computationally, subject to plane wave pumping. Linear stability techniques are deployed to obtain the threshold spatial instability spectrum predicting the emergence of static patterns, and which exhibits a discrete-island type of structure. Simulations then consider the full dynamics of the system, testing theoretical analyses in the cases of instantaneous and diffusive medium responses. The emergence of both simple (single-scale) and fractal (multi-scale) spatial patterns is demonstrated, and specialist software used to assist with quantifying their dimension characteristics in terms of system parameters. The first steps are also taken towards understanding the role played by nonparaxiality when considering spatial fractal pattern formation in dispersive systems with a finite light-medium interaction length. The classic Schr¨odinger-type governing equations for bulk ring cavities are reformulated as Helmholtz-type problems, capturing a family of higher-order nonlinear effects that describe wavelength-scale spatial structure in the circulating field.
83

Don't soil your chances with solar energy| Experiments of natural dust accumulation on solar modules and the effect on light transmission

Boyle, Liza 31 December 2015 (has links)
<p> Dust accumulation, or soiling, on solar energy harvesting systems can cause significant losses that reduce the power output of the system, increase pay-back time of the system, and reduce confidence in solar energy overall. Developing a method of estimating soiling losses could greatly improve estimates of solar energy system outputs, greatly improve operation and maintenance of solar systems, and improve siting of solar energy systems. This dissertation aims to develop a soiling model by collecting ambient soiling data as well as other environmental data and fitting a model to these data.</p><p> In general a process-level approach is taken to estimating soiling. First a comparison is made between mass of deposited particulates and transmission loss. Transmission loss is the reduction in light that a solar system would see due to soiling, and mass accumulation represents the level of soiling in the system. This experiment is first conducted at two sites in the Front Range of Colorado and then expanded to three additional sites. Second mass accumulation is examined as a function of airborne particulate matter (PM) concentrations, airborne size distributions, and meteorological data. In depth analysis of this process step is done at the first two sites in Colorado, and a more general analysis is done at the three additional sites. This step is identified as less understood step, but with results still allowing for a general soiling model to be developed. Third these two process steps are combined, and spatial variability of these steps are examined. The three additional sites (an additional site in the Front Range of Colorado, a site in Albuquerque New Mexico, and a site in Cocoa Florida) represent a much more spatially and climatically diverse set of locations than the original two sites and provide a much broader sample space in which to develop the combined soiling model. Finally a few additional parameters, precipitation, micro-meteorology, and some sampling artifacts, are cursorily examined. This is to provide a broader context for these results and to help future researchers in understanding the strengths and weaknesses of this dissertation and the results presented within.</p>
84

The use of in-situ ion-irradiation/TEM techniques to study radiation damage in SiC

Pawley, C. January 2014 (has links)
SiC is a material currently under consideration to be used in future generations of fission and fusion reactors where it will be subjected to high temperatures and significant fluxes of energetic neutrons. The work reported in this thesis aims to answer some outstanding issues of the behaviour of SiC at high temperature during irradiation by high-energy neutrons in combination with a build-up of helium (from both transmutation reactions and by direct implantation). These processes have been simulated by in-situ ion-irradiation / TEM at the MIAMI and JANNuS facilities. This thesis contains the results of experiments which investigated the nucleation and growth of helium bubbles in SiC and the behaviour of these helium bubbles under high energy heavy ion-irradiation. Our conclusions are that helium bubbles in SiC are extremely stable at high temperatures and during high-energy ion-irradiation. However, we have discovered that there is a significant effect on the bubbles attributable to either electron beam irradiation alone or the synergistic effect of the electron beam and ionirradiation which causes helium bubbles to shrink.
85

Structure, Morphology, and Electrochemical Properties of Transition Metal Oxide, Hydroxide, and Phosphate Nanomaterials for Energy Storage

Lee, Gyeonghee January 2016 (has links)
<p>Energy storage technologies are crucial for efficient utilization of electricity. Supercapacitors and rechargeable batteries are of currently available energy storage systems. Transition metal oxides, hydroxides, and phosphates are the most intensely investigated electrode materials for supercapacitors and rechargeable batteries due to their high theoretical charge storage capacities resulted from reversible electrochemical reactions. Their insulating nature, however, causes sluggish electron transport kinetics within these electrode materials, hindering them from reaching the theoretical maximum. The conductivity of these transition metal based-electrode materials can be improved through three main approaches; nanostructuring, chemical substitution, and introducing carbon matrices. These approaches often lead to unique electrochemical properties when combined and balanced.</p><p>Ethanol-mediated solvothermal synthesis we developed is found to be highly effective for controlling size and morphology of transition metal-based electrode materials for both pseudocapacitors and batteries. The morphology and the degree of crystallinity of nickel hydroxide are systematically changed by adding various amounts glucose to the solvothermal synthesis. Nickel hydroxide produced in this manner exhibited increased pseudocapacitance, which is partially attributed to the increased surface area. Interestingly, this morphology effect on cobalt doped-nickel hydroxide is found to be more effective at low cobalt contents than at high cobalt contents in terms of improving the electrochemical performance.</p><p>Moreover, a thin layer of densely packed nickel oxide flakes on carbon paper substrate was successfully prepared via the glucose-assisted solvothermal synthesis, resulting in the improved electrode conductivity. When reduced graphene oxide was used for conductive coating on as-prepared nickel oxide electrode, the electrode conductivity was only slightly improved. This finding reveals that the influence of reduced graphene oxide coating, increasing the electrode conductivity, is not that obvious when the electrode is already highly conductive to begin with.</p><p>We were able to successfully control the interlayer spacing and reduce the particle size of layered titanium hydrogeno phosphate material using our ethanol-mediated solvothermal reaction. In layered structure, interlayer spacing is the key parameter for fast ion diffusion kinetics. The nanosized layered structure prepared via our method, however, exhibited high sodium-ion storage capacity regardless of the interlayer spacing, implying that interlayer space may not be the primary factor for sodium-ion diffusion in nanostructured materials, where many interstitials are available for sodium-ion diffusion.</p><p>Our ethanol-mediated solvothermal reaction was also effective for synthesis of NaTi2(PO4)3 nanoparticles with uniform size and morphology, well connected by a carbon nanotube network. This composite electrode exhibited high capacity, which is comparable to that in aqueous electrolyte, probably due to the uniform morphology and size where the preferable surface for sodium-ion diffusion is always available in all individual particles.</p><p>Fundamental understandings of the relationship between electrode microstructures and electrochemical properties discussed in this dissertation will be important to design high performance energy storage system applications.</p> / Dissertation
86

A Utility-Scale Deployment Project of Behind-the-Meter Energy Storage for Use in Ancillary Services, Energy Resiliency, Grid Infrastructure Investment Deferment, and Demand-Response Integration

Wilson, Joseph Nathanael 09 June 2016 (has links)
Electric utilities are increasingly incentivized to integrate new renewable energy generation resources to their systems; however, operations-related issues arise due to the non-dispatchable and stochastic nature of these renewable energy sources. These characteristics lead to a variety of issues for utilities, among which are voltage fluctuations, balancing dispatch against ramping events, short-duration power fluctuations, and the need to invest in peaking generation facilities just to accommodate the renewable energy. A traditional solution to these issues is to employ renewable generation-following techniques using either newly constructed gas peaking plants, or by shifting existing generation resources to this following responsibility. Unfortunately, use of these traditional methods introduces a new set of issues; namely, wear-and-tear due to more frequent cycling, reduced capacity factors, decreased plant efficiency, and additional investment in large-scale captital infrastructure. This thesis proposes an alternate solution: a utility-owned and utility-managed battery energy storage system sited on residential customer premises, deployed at scale to create a 200MW / 1320MWh distributed network of Residential Battery Energy Storage Systems (ResBESS). In partnership with Portland General Electric (PGE) stakeholders, a conceptual design was prepared for a ResBESS unit, a laboratory prototype of a single such storage system was constructed, and an alpha prototype is now being installed in a field demonstration project in Milwaukie, Oregon within PGE's service territory. The motivations, design constraints, and design methodology of the laboratory prototype are presented and discussed, and preliminary work from the field prototype build is examined to demonstrate the results of the thesis project.
87

The modification of thin film surface structure via low temperature atmospheric pressure CVD post process treatment

Thomson, M. January 2013 (has links)
In photovoltaic thin film cells, a transparent conducting oxide (TCO) layer is required to transport current. The most common TCOs used are F:SnO2 (fluorine doped tin oxide), ZnO (zinc oxide) and ITO (indium doped tin oxide). ZnO is normally deposited in a vacuum based process, sputtering or low pressure chemical vapour deposition (LPCVD). Atmospheric pressure chemical vapour deposition (APCVD) is an attractive alternative for ZnO deposition. A critical parameter for TCOs in photovoltaic thin films is the surface morphology which defines the optical scattering properties. The ability to control the spectral sensitivity and degree of scattering are both important process parameters for high performance cells. This thesis investigates APCVD for film growth of ZnO plus dopants (fluorine and aluminium), and the effects of atmospheric pressure plasma etching of ZnO and F:SnO2. ZnO was deposited in multiple system geometries all based on thermal activated CVD. The oxidant source purity is shown to be critical for stable growth at higher temperatures required for dopant incorporation. A fundamental problem was encountered with fluorine doping, whereby the films would crack beyond a critical thickness. A solution was found with the development of a F:SnO2 and F:ZnO composite stack. Photovoltaic testing of this hybrid TCO was encouraging, showing the potential benefit of the composite structure. Modification of the surface morphology was achieved by atmospheric pressure plasma, based on a dielectric barrier discharge configuration. This novel system enables the etching of TCO films without the introduction of hazardous wet chemistry. In this thesis the effects of etching regime and feedgas composition are studied and an etching mechanism is proposed. Isolation of the etching environment enabled investigation into the feed gas mixture, demonstrating which were critical for etching. Both materials showed a dependence on the feed gas mixture for etching, with F:SnO2 requiring HCl and O2 and H2O for ZnO.
88

A first-principles investigation on substitutions in the carbon allotropes glitter and graphene

Baldissin, G. January 2013 (has links)
In the literature, a number of syntheses of carbon materials under extreme condition exhibit the presence of a carbon phase, called n-diamond, whose crystal structure remains unclear. Several crystallographic arrangements have been proposed, which are critically assessed in this work with regards to dynamical stability. It is shown that tetragonal carbon (glitter) is the only structure that satisfies this criterion. Glitter is a metallic 3-, 4-connected allotrope containing 1,4-cyclohexadieneoid units, giving a high energy meta- stable phase. Applying a fully first principles approach, which couples den- sity functional theory (DFT) calculations and Ising-like parameterisation, the possibility of stabilising the structure with nitrogen, boron and silicon substitutions has been investigated, finding that there are arrangements with negative formation energy. These novel arrangements have been tested for vibrational stability, whereby it has been proven that they are dynamically stable. Moreover a bandgap opens, leading to semiconductor bulk materials based on Si, C, B and N. Graphene, a carbon allotrope having the so-called chicken-net structure, is a zero-bandgap semiconductor, which make it promising for nano-electronic applications. However tuning and modifying the bandgap would expand the range of possible applications, in particular for post-silicon transistors. The effect of B substitutions in the graphene lattice has been studied, in terms of stability and electronic structure. The doping at low B concentration has been studied with a direct DFT approach while the effect at higher concentration has been studied with the above-mentioned coupled approach. Novel arrangements, that have semiconductor behaviour, have been proven to be dynamically stable at 0 K. The effect of a second B-C layer has also been investigated, finding that is effective on bandgap tuning.
89

Ultra-broadband frequency generation in a cavity confined Raman medium

Rose, C. S. January 2013 (has links)
Throughout the past few decades, science has progressed towards the ability to probe many extremely fast processes and a large amount of research has been aimed at the area of few-femtosecond pulse generation. This thesis describes the generation of coherent broadband radiation through two-colour pumping of molecular hydrogen confined to a unidirectional ring cavity, and the subsequent synthesis of high peak power and few-femtosecond pulses. A set of normalised semi-classical field equations are derived in Bloch form describing the process of ultra-broadband multi-frequency Raman generation or UMRG, and a 3-wave gain suppression analysis is derived from a subset of the plane wave UMRG field equations which describes gain suppression within the ring cavity in terms of both medium and cavity parameters. The gain suppression analysis is further generalised to include finite levels of linear two-photon frequency detuning of the pump beams. Simulations of the plane wave ultra-broadband multi-frequency Raman (UMRG) equations show that a broad frequency spectrum of mutually coherent sideband can be generated. The inverse Fourier transform of spectra generated in this way yields a train of high power near Fourier limited pulses in the time domain which can range from a few-femtoseconds in duration to tens of attoseconds with repetition rates equal to the Raman transition frequency. Pulses synthesised in this way are limited only by the level of medium dispersion, the reflection bandwidth of the chosen coupling mirror and the chosen Raman medium. Simulations of the transverse UMRG equations within the ring cavity geometry have shown ring cavity enhanced UMRG to be resilient to transverse effects such as finite beam width, beam diffraction and the transverse beam separation of the applied pump beams.
90

A novel technique for measuring and sensing rain

Kundgol, A. S. January 2015 (has links)
Rainfall passing over a given area is a highly dynamic process; it changes constantly in form and intensity. It varies constantly on short spatial and temporal scales that makes real time measurements of the amount of rainfall challenging. Measuring and sensing rain is important to be able to understand and control our urban environment. Traditionally, rainfall analysis for hydrologic modelling use spatial measurements collected at various sparsely spread observation points using rain gauges working on various principles such as weighing type, tipping bucket, capacitive type etc. An accurate representation of spatial model of rainfall is essential for hydrological operational purposes such as forecasting of river flow, flood irrigation planning and modelling of catchment areas. Measurement of drop size distribution are also exploited to investigate microphysics of precipitation and to improve rainfall remote sensing estimation techniques. However, the high initial costs of convectional rain gauges prevent collection of data with high spatial resolution. The research looks at investigating the sensor stack to be a part of an integrated sensor approach to develop a device architecture for the development of low cost integrated rain sensing and measuring the rain. The device architecture consists of three main stacks – energy generation layer, sensing layer, processing layer. The raindrop on impact causes vibration on the device surface. This force exerted by the raindrop causes a deflection and is measured indirectly by the use of a thin film piezo sensor. As part of the work, we find there is a good correlation between the vibrations caused and the size or volume of the raindrop by indirectly measuring the impact force of the raindrop. The working range of the device is between 100hz and 2000hz, which includes the first modal peak of the impact that acts as an amplification to the drop's impact. Using this information, the device is able to calculate the raindrop size distribution and the rain intensity. Calibration of the device is key as we are measuring the impact force of the rain drops and correlating it to the size of the drop. Primary, not all rain drops will fall on the device at terminal velocity (the main assumption for calibration of the device), as the fall velocity of the droplet may also be affected by the wind. Secondly, the spatial variation of the frequency response function in Volts/Newton in decreasing order from the centre of the plate.

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