No description available.

Research into the modelling and analysis of microstrip patch antenna have been reported in many studies. These include Transmission Line Modelling, Cavity Modelling, Coplanar Multiport Modelling and Full wave Modelling. Since the electromagnetic field elements are time harmonic, the phasor-form of the Maxwell field equations is used. In this thesis results are presented of the research that has been carried out into the segmental approach for the analysis of the microwave patch antennas. The segmental approach includes the "Segmentation" and the "Desegmentation" methods. In the segmentation method two distinct structural forms have been identified, cascade and shunt types. In the cascade type all consecutive segment elements share a common boundary, while for the shunt type, all appended segment elements have no common boundary. In the case of the shunt type structure a generalised input impedance matrix formula, for any number of appended segment elements, has been obtained. For the desegmentation method a generalised input impedance for any number of deleted segment elements, has been obtained. The above research studies have been applied in the design of a circular polarised two corner deleted square patch microstrip antenna with a single feed. For this structure the design involves both square and triangular patch geometries. The overall patch geometry for circular polarised is determined using perturbation analysis to determine the size of the deleted triangular segment elements. New computationally efficient impedance coupling expressions for the interconnecting port impedances on a rectangle, and, on a right angled isosceles triangle shaped antenna patch have been derived. In the determination of the input impedance of the overall antenna structure the coupling impedances constitute the elements of the individual segment coupling matrices. The matrices are used in a general multiport matrix circuit analysis to obtain the input impedance formula. It is established that, where applicable, the desegmentation method is computationally more efficient than the segmentation method. The new results obtained have been applied to the design of a corner deleted square patch antenna, and, the design procedure is fully described. The computer program implementation evaluates the perturbation quantity, and, the antenna input impedance. The structural properties of the coupling matrices, which are used for efficient computation, are described in detail. All the results from the above work show close agreement with full-wave software simulation and practical results. Significant research achievements: Both segmentation and desegmentation methods have been studied and it has been shown that the desegmentation approach, when applicable, is in general significantly more computationally efficient. In the segmentation method two structural forms, cascade and shunt have been identified. In the latter case a new generalised input impedance matrix formula has been obtained for any number of appended segment elements. A new generalised input impedance matrix formula has been obtained for any number of deleted segment elements in the desegmentation method. New computationally efficient expressions for the coupling impedances have been derived and used in test applications. New computationally efficient expressions for the offset input impedance of a linear polarised rectangular patch, and, an isosceles right-angled triangular patch have been derived and experimentally verified. A program implementing the design procedure for the corner-deleted truncated square patch circular polarised microstrip antenna has been constructed using MATHCAD programming.

The aim of the work presented in this thesis was to develop CuInSe2 (CIS) and CuIni_„Al„Se2 (CIAS) thin films for application in photovoltaic (PV) solar cells. The purpose of the addition of aluminium (Al) in CIS thin films was to modify the energy band gap of the thin films to be nearer to the optimum for PV energy conversion and to replace the less abundant element, gallium (Ga) in CuIni_,,Ga,Se2 (CIGS) solar cells. This also makes possible the production of tandem solar cells using CIAS to make the wide energy band gap top cell and the CIS to make the narrow energy band gap lower cell. The use of very thin CIS and CIAS absorber layers in solar cell structures was also investigated; the aim was to reduce the amount of indium (In) in cell production. The CIS and CIAS absorber films were prepared by a sequential two step method in which Cu-In and Cu-In-Al precursor layers were magnetron sputter deposited onto Mo-coated soda lime glass (SLG) substrates; the CIS or CIAS was then formed by heating in a selenium (Se) containing environment. Thin film solar cells were developed in the substrate configuration and had the structure Ni-Al/Indium tin oxide (ITO)/i-ZnO/CdS/CIAS/Mo/SLG. In order to achieve high efficiency solar cells it is an important to optimse the back contact molybdenum (Mo) layer, the absorber layer, the CdS buffer layer, the window layer and top contact layers. The work described in this thesis focused on the optimisation of the back contact and absorber layers. The thin films were characterised mainly using X-ray diffraction (XRD), energy dispersive X-ray analysis (EDS), scanning electron microscopy (SEM), secondary ion mass spectroscopy (MiniSIMS), atomic force microscopy (AFM) and using spectroscopy measurements to investigate the effect of processing conditions on the composition, crystal structure, surface morphology and the optical properties of the films. The solar cells were characterised by current-voltage (/- V) and incident photon-to-photocurrent conversion efficiency (IPCE) measurements. Both Mo single and bilayer structures were investigated. It was found that single layers had better properties than Mo bilayers. The optimisation of the Mo deposition sputtering process yielded Mo layers which had good adherence and were conformal to the glass substrates, had low resistivity (29 if .cm), were pin hole free and had good crystallinity. The influence of Cu-In precursor layers with thicknesses in the range 90-400 nm on the microstructure of the CIS thin films (thicknesses in the range 400-1600 nm) was investigated. Solar cells fabricated from the CIS films of thicknesses 500 nm and 900 nm yielded highest cell conversion efficiencies of 4.3% and 8.2%, respectively. The selenisation of the magnetron sputter deposited Cu-In-Al precursor layers was carried out at a temperature of 550°C. Films were poor in surface quality and adhesion. Films prepared from the precursor layer with n [(Al/(Al+In))] = 0.21 had a non-uniform Al depth profile towards the bottom of the film. Although the film was found to be photoactive its effective energy band gap was 0.98 eV suggesting the properties of CIS. This confirmed incomplete mixing of Al in the thin films which was considered to be segregated at the bottom of the film. The thinner layers of Cu-In-Al precursors with thicknesses in the range 0.55¬1.00 gm and n [(Al/Al+In)] in the range 0.28-0.54 were magnetron sputter deposited. The precursor layers showed the prominent binary A1Cu4 compound with a uniform distribution of Al in the layer. Thin films converted from these precursor layers of thicknesses in the range 1.3-2.0 pm were fairly uniform in surface structure. Films with x 0.2 were found to have an energy bandgap of 1.10 eV and were also photoactive. Solar cells fabricated from this absorber film yielded a highest cell efficiency of 4.9%. Environmental impact assessments have been made on materials and the processes used in the fabrication of CIS and CIAS.

This work forms a part of a large EU project (InnovaTiAl) designed to increase the service temperature (up to 1273 K) of TiAl based intermetallics (Ti45Al8Nb) coated with high performance surface layers for applications in power generation and also in aerospace components. In this thesis the high temperature corrosion behaviour of some of these newly developed high performance coatings deposited on Ti45Al8Nb alloys using UBM and HIPIMS/UBM has been studied. The coatings studied included intermetallic coatings: TiAlCr, TiAlCrY, Al2Au, and ceramic coatings: CrAl2%YN, TiAlYN/CrN+Al2O3, TiAlN+Al2O3, CrAlYN/CrN+CrAlYON coated Ti45Al8Nb etched by Cr, CrAlYN/CrN+CrAlYON coated Ti45Al8Nb etched by CrAl, CrAlYN/CrN+CrAlYON coated Ti45Al8Nb etched by Y, CrAlYN/CrN coating Y etch, CrAl (thin), CrAlYN/CrN coating Cr etch, CrAl (thin), CrAlYN/CrN coating, Y etch, CrAlY (thick) coated Ti45Al8Nb. High temperature corrosion investigations were carried out by the exposing the coated materials in oxidising (static air, pO2 = 21278.25 Pa), sulphidising (pS2 = 10-1 Pa, and pO2 = 10-18 Pa) and hot corrosion (20%NaCl/80%Na2SO4) environments at temperatures range 1023 – 1223 K. The long term oxidation studies have been performed up to 5000 hours at 1023 K. Weight change data have been used to determine the corrosion kinetics. SEM studies have provided information on morphology; EDS analyses have given the information on concentration profiles and phase contents have been obtained by XRD analyses. The excellent high temperature oxidation resistance has been achieved for the CrAl2%YN coating at temperature rage 1023 – 1123 K for 500 hours. Also TiAlCr and TiAlCrY have shown moderate degree of corrosion resistance in oxidising environment after 500 hours of exposure at temperature range 1023 – 1223 K. The sulphidation experiments for 1000 and 675 hours at 1023 K and 1123 K respectively showed that the uncoated material developed a multilayered thick scale with poor resistance to sulphidation. The ceramic coatings developed a good protective Al2O3/Cr2O3 on places where the coatings remained intact and did not undergo cracking. However due to the cracks in the top coat, the development of non protective TiO2 occurred at 1023 and 1123 K. Hot corrosion studies performed at 1023 K for 150 hours under this thesis showed that all exposed materials (CrAl2%YN, TiAlN+Al2O3, and TiAlYN/CrN+Al2O3) suffered uneven attacks (crack formation, spallation, and the lack of Al2O3 formation). Interdiffusion studies of mass transport have been performed by GDM on TiAlCrY coated alloy after 500 hours oxidation at 1023 and 1123 K. A reasonable degree of agreement between the experimental and the simulated profiles has been achieved.

<p> Hypotheses were developed and tested to measure the cable modems operational metrics response to a reconfiguration of the cable modems' transmitted RF applied to the CMTS. The purpose of this experiment was to compare two groups on the use of non-federal RF spectrum to determine if configuring the cable modems' transmitted RF from 25.2 MHz, at 6.4 MHz Wide, 64 QAM and 31 MHz, at 6.4 MHz Wide, 64 QAM to 34.8 MHz, 6.4 MHz Wide, 64QAM improved the data services operational metrics measured by a wire line service operator to determine the quality of their product. The experiment tests the theory; configuring cable modems' transmitted RF to 34.8 MHz, 6.4 MHz Wide, 64QAM on the CMTS significantly impacted a cable modem's operational metrics, and as a result, increased operational effectiveness. </p><p> A randomized experiment on 117,084 cable modems resulted in a significant impact on SNR and transmit rates but did not present a significant impact on error rates and the trouble call metrics. The results showed that reconfiguring the cable modems' transmitted RF from 25.2 MHz, at 6.4 MHz Wide, 64 QAM and 31 MHz, at 6.4 MHz Wide, 64 QAM, to 34.8 MHz, 6.4 MHz Wide, 64QAM did significantly increase the SNR and transmit rates but did not significantly impact error rates and the trouble call truck roll metrics. The results are discussed in relation to other work implicating engineering RF management strategies and the impact on the cable modems operational metrics by reconfiguring the cable modems' RF from the lower ends of the RF spectrum into the middle of the RF spectrum configured on a wire line service operator's CMTS.</p>

Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009. / Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3595. Adviser: Ilesanmi Adesida. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

No description available.

<p> Communities worldwide face water supply challenges and often seek alternative sources of water. Recycled water is an alternative generated from wastewater to reduce non-potable uses of high quality water supplies for irrigation, industrial processes, power plant cooling, and toilet flushing. Researchers have recommended constructing the systems in new communities to reduce capital investment. The implementation of these systems is often financially difficult to justify within existing communities. Orange County Water District constructed a recycled water system, Green Acres Project (GAP), within existing communities in northern Orange County, California. The system delivers recycled water to four cities, reduces seawater intrusion, creates a benefit from a wastewater stream, and diversifies the region&rsquo;s water portfolio. As is common among recycled systems, the GAP has operated at a financial loss since its construction in the early 1990&rsquo;s. Through water sale revenues and a subsidy program, the District has been able to cover operational and maintenance costs but not capital. This study presents hydraulic and financial modeling to better understand the current GAP system and proposed changes. EPANET has been used to simulate five scenarios that include current operation, known future demand changes, breaking distribution loops, and increasing demand to balance finances. Analyzed financial scenarios include continued operation, breakeven finances, change in treatment technology, abandonment of system, and changing the local definition of recycled water. Recommendations to improve financial and operational efficiencies, challenges, and lessons learned from the GAP system are presented so other communities investigating implementation of recycled water programs may become better informed.</p>

<p> Extreme risks associated with natural and man-made disasters involve disruptions in the production of goods or provision of services in interdependent systems. The reduced supply of critical goods and services will degrade "as planned" production outputs and create ripple effects of direct and indirect disruptions. Input-output modeling evaluates the propagation of disaster consequences by quantifying the associated economic risks of disruption, namely economic loss and inoperability, for multi-sectoral economic regions. The thesis enhances the reliability of these risk estimates by formulating a stochastic inventory-based risk assessment model using a multi-objective optimization framework for minimizing (i) economic losses, and (ii) sector inoperability. The research utilizes inventory-to-sales ratio data from the Bureau of Economic Analysis for modeling uncertainty in the levels of finished goods inventory and the beta distribution to integrate uncertainty in decision-maker preferences associated with the multi-objective framework. The framework focuses on the development of a holistic, flexible and scalable decision support system through a Dynamic Cross Prioritization Plot (DCPP) for identifying inventory enhancement opportunities among critically disrupted systems that is applicable to different regions and disaster scenarios. </p>

<p> In this thesis, the author presents a feasibility study of methods to modernize the port crane systems with the application of haptic (force) feedback assistive technology to assist the crane operator in the container handling process. The assistive technology provides motion guidance to the operator that could help increase the safety and productivity of the system. The technology of haptic feedback is successful in applications such as gaming, simulators etc., and has proven quite efficient in alerting the user or the operator. This study involves the implementation of haptic feedback as an assistive mechanism through a force-feedback joystick used by the operator to control the motion of a scaled port crane system. The haptic feedback system has been integrated to work with the visual feedback system as part of this study. The visual feedback system shares information needed to trigger the haptic (force) feedback display on the joystick. The force feedback displayed on the joystick has been modeled on Hooke's law of spring force. The force feedback and the visual feedback form a motion guidance system. The integrated system has been implemented and tested on a lab-scale testbed of a gantry crane. For experimental purposes, this concept has been tested on a PC-based Windows platform and also on a portable single board Linux-based computer, called the Beagleboard platform. The results from test runs on both the platforms (PC and Beagleboard using ARM processor) are reported in this study. 2</p>