The objectives of this work were to investigate, design and implement beam steering antenna arrays for mobile and wireless applications using the genetic algorithm (GA) and particle swarm optimisation (PSO) techniques as optimisation design tools. Several antenna designs were implemented and tested: initially, a printed dipole antenna integrated with a duplex RF switch used for mobile base station antenna beam steering was investigated. A coplanar waveguide (CPW) to coplanar strip (CPS) transition was adopted to feed the printed dipole. A novel RF switch circuit, used to control the RF signal fed to the dipole antenna and placed directly before it, was proposed. The measured performance of the RF switch was tested and the results confirmed its viability. Then two hybrid coupled PIN diode phase shifters, using Branchline and Rat-Race ring coupler structures, were designed and tested. The generation of four distinct phase shifts was implemented and studied. The variations of the scattering parameters were found to be realistic, with an acceptable ±2 phase shift tolerance. Next, antenna beam steering was achieved by implementing RF switches with ON or OFF mode functions to excite the radiating elements of the antenna array. The switching control process was implemented using a genetic algorithm (GA) method, subject to scalar and binary genes. Anti-phase feeding of radiating elements was also investigated. A ring antenna array with reflectors was modelled and analysed. An antenna of this type for mobile base stations was designed and simulation results are presented. Following this, a novel concept for simple beam steering using a uniform antenna array operated at 2.4 GHz was designed using GA. The antenna is fed by a single RF input source and the steering elements are reactively tuned by varactor diodes in series with small inductors. The beam-control procedure was derived through the use of a genetic algorithm based on adjusting the required reactance values to obtain the optimum solution as indicated by the cost function. The GA was also initially used as an optimisation tool to derive the antenna design from its specification. Finally, reactive loading and time modulated switching techniques are applied to steer the beam of a circular uniformly spaced antenna array having a source element at its centre. Genetic algorithm (GA) and particle swarm optimisation (PSO) processes calculate the optimal values of reactances loading the parasitic elements, for which the gain can be optimised in a desired direction. For time modulated switching, GA and PSO also determine the optimal on and off times of the parasitic elements for which the difference in currents induced optimises the gain and steering of the beam in a desired direction. These methods were demonstrated by investigating a vertically polarised antenna configuration. A prototype antenna was constructed and experimental results compared with the simulations. Results showed that near optimal solutions for gain optimisation, sidelobe level reduction and beam steering are achievable by utilising these methods. In addition, a simple switching process is employed to steer the beam of a horizontally polarised circular antenna array. A time modulated switching process is applied through Genetic Algorithm optimisation. Several model examples illustrate the radiation beams and the switching time process of each element in the array.

No description available.

<p>  </p> <p>Knowledge of the displacement and deformation fields beneath foundation elements obtained from carefully executed experiments is required to validate state-of-the-art numerical simulations, which in turn enable the development of better foundation design methods. This dissertation presents the results of an experimental program in which load tests were performed on model footings in a half-cylindrical calibration chamber with a transparent viewing window across its diameter. The digital image correlation (DIC) method was used to obtain the strain and displacement fields in the soil from digital images taken during the tests. Tests performed on both smooth and rough footings show a significant dependence of resistance on footing base roughness, with the DIC results providing insight into the reasons for that dependence. The experimental bearing capacity results are used to validate a previously proposed method in which an equivalent friction angle is used for calculation of the bearing capacity of footings in sand.</p> <p>Schmertmann's method is one of the traditional methods for estimating the settlement of axially loaded footings in sand using cone penetration test (CPT) data. The method was developed for footings placed on the surface of a single, uniform sand layer; it assumes a depth of influence below the footing base within which most of the soil deformations take place and an influence diagram to quantify the influence factor as a function of depth. However, the literature contains limited information on the strain influence diagrams for footings on layered sands, and, as a result, there is no way to accurately account for the effect of sand layering on footing settlement. In this study, Schmertmann's approach for calculating the strain influence factor is modified to account for the effect of two sand layers with varying thickness and relative density. Penetration experiments were performed using a half-square model footing (width <em>B</em> = 90 mm) placed on the surface of both single and two-layered (dense over medium-dense and medium-dense over dense), air-pluviated, silica sand samples prepared inside a half-cylindrical calibration chamber designed for digital image correlation (DIC) analysis. The test results indicate that both the thickness and relative density of the top sand layer (the layer in contact with the footing base) affect the parameters of the strain influence diagram. For dense sand over medium-dense sand, the depth to the peak strain influence factor varies with the thickness of the dense layer; however, when the thickness of the dense layer is 1.5<em>B</em> or greater, the strain influence diagram is similar to that obtained for a single, uniform sand layer. In contrast, for medium-dense sand over dense sand, the peak value of the strain influence factor varies with the thickness of the medium-dense layer up to a value of 1<em>B</em>. Based on the results obtained in this study, new strain influence diagrams are proposed for settlement calculation of square footings on two-layered sand profiles. The proposed method for estimation of footing settlement in layered sand is validated against measured data obtained from a full-scale, instrumented footing load test reported in the literature. </p> <p>The expressions for the shape and depth factors available in the literature for bearing capacity calculation are mostly empirical and are based on results obtained using limit analysis or the method of characteristics assuming a soil that is perfectly plastic following an associated flow rule. This study presents the results of an experimental program in which load tests were performed on model strip and square footings in silica sand prepared inside a half-cylindrical calibration chamber with a transparent visualization window. The results obtained from the model footing load tests show a significant dependence of footing penetration resistance on embedment depth. The load test results were subsequently used to determine experimentally the shape and depth factors for model strip and square footings in sand. To obtain the displacement and strain fields in the sand domain, the digital image correlation (DIC) technique was used to analyze the digital images collected at different stages during loading of the model footing. The DIC results provide insights into the magnitude and extent of the vertical and horizontal displacement and maximum shear strain contours below and around the footing base during penetration.</p> <p>The loading of a footing in sand generates substantial shear bands as a mechanism for failure develops with the formation of slip surfaces. The interaction of sand particles in the shear band governs its constitutive response to loading. This study provides the results of loading experiments performed under different conditions on half-square model footings (width <em>B</em> = 90 mm) in dense air-pluviated silica sand samples prepared in a half-cylindrical calibration chamber equipped with an observation window that allows collection of images of the sand domain during testing. Two sands (Ottawa sand and Ohio Gold Frac sand) with different roundness (angularity) were used to perform these experiments. The digital image correlation (DIC) technique was used to obtain the incremental strain fields in the sand domain. The zero-extension line (ZEL) concept was then used to study the shear strain localization process and to obtain the orientation of the shear bands from analysis of the incremental strain fields. The results show that sand particle morphology, footing surface roughness, load eccentricity, and depth of embedment of the model footing have an impact on the dominant shear band patterns that develop below the model footings, and, as a result, all of these factors affect the unit bearing capacity of footings. The estimated thickness <em>t</em>s of the shear band from the experiments is approximately 6<em>D</em>50 for Ottawa sand and approximately 8<em>D</em>50 for Ohio Gold Frac sand. </p>

No / To mitigate potential interferences with coexisting wireless systems operating over 3.3-3.6 GHz, 5.15-5.35 GHz, or 5.725-5.825 GHz bands, four novel band-notched antennas suitable for ultra-wideband (UWB) applications are proposed. These include UWB antennas with a single wide notched band, a single narrow notched band, dual notched bands, and triple notched bands. Each antenna comprises a half-circle shaped patch with an open rectangular slot and a half-circle shaped ground plane. Good band-notched performance is achieved by using high permittivity and low dielectric loss substrate, and inserting quarter-wavelength horizontal/vertical stubs or alternatively embedding quarter-wavelength open-ended slots within the feed line. The results of both simulation and measurement confirm that the gain suppression of the single and multiple band-notched antennas in each desired notched band are over 15 dB and 10 dB, respectively. The radiation pattern of the proposed triple band-notched design is relatively stable across the operating frequency band.

<p dir="ltr">Over the past three to four decades, mechanically stabilized earth (MSE) walls have gained preference over other wall types due to the several advantages that they offer, such as ease of construction, flexibility to accommodate large differential settlements, architectural versatility, and low cost per unit area of wall face. Because of these advantages, several departments of transportation in the United States have adopted MSE walls to serve as abutments for highway and railway bridges. While the response of conventional MSE walls has been studied both experimentally and numerically, comparatively less work has been done to investigate the behavior of MSE walls used as abutments for bridge support. This dissertation presents a case study of the performance of a pile-supported, MSE bridge abutment in Whitestown, Indiana, during construction and while in service. A zone near the middle of the east MSE abutment wall was instrumented with earth pressure cells, strain gauges, inclinometers, and crackmeters to investigate the transfer of dead and live loads from the bridge to the foundation elements (pile cap and piles), and to assess the performance of the MSE abutment wall under these loading conditions. The data was collected continuously, both during and after construction, using multiplexers and dataloggers powered by solar panels. The values of key parameters used in MSE wall design were determined from the instrumentation results and compared with those obtained using design methods available in the literature. In addition, the measured dead loads carried by the instrumented piles were compared with the estimated dead loads used in the design of the MSE abutment. After the bridge was constructed, a live load test was performed by parking twelve triaxle trucks at different locations along the approach to the instrumented MSE abutment as well as on the bridge deck near the abutment. Finally, a series of three-dimensional finite element analyses of MSE walls and pile-supported MSE abutments were performed using a two-surface-plasticity constitutive sand model. The lateral stresses on the back of the wall facing and the reinforcement tensile loads obtained from the FE analyses were found to be in good agreement with those measured at the end of construction of the Whitestown MSE abutment. The results obtained from the FE analyses highlight the influence of wall height, backfill soil type, and pile offset on the magnitude and distribution of the lateral stresses on the back of the wall facing and the maximum tensile loads in the reinforcements.</p>

The Appalachian coal mining region is subject to a number of environmental and economic problems; many are a result of the steeply sloping topography. The extensive surface mining activities in the area appear to offer the opportunity to produce more favorable landforms at minimum marginal costs. Yet, despite this apparent opportunity and the success of research efforts to develop improved mine soil construction and revegetation techniques, the majority of the mining and reclamation activities in the Virginia coal region are carried out using conventional methods: reconstructing steeply sloping mining areas to their approximate original contours. The purpose of this research was to estimate the costs of coal surface mine reclamation methods designed to prepare mined lands for improved use in areas of steeply sloping topography. During the course of this research, a computer-based mining and reclamation cost estimating system was developed. COSTSUM is a set of seven programs designed to analyze data from active surface mining sites to determine spoil handling and reclamation costs. OPSIM is a surface mining simulator designed to estimate the differences in spoil handling costs among reclamation and postmining landform alternatives. This cost-estimating system was utilized during an intensive study of mining and reclamation costs at a surface mining site in Wise County, Virginia, where a number of improved reclamation practices were implemented. At this site, a steeply sloping premining topography was transformed to a postmining landform containing an extensive near-level area covered with deep, uncompacted, potentially productive mine soils. Analysis of daily records of operations revealed that the cost of mining and reclaiming this site was comparable to industry average costs in the area in spite of departure from conventional methods. The results of simulation procedures indicated that the cost of mining so as to produce this landscape was less than than the estimated cost of conventional mining methods. Since the topography of the site is typical of surrounding areas, there are opportunities to produce near-level landforms with deep, productive soils as a byproduct of coal surface mining activities. / Ph. D.

In dieser Dissertationen werden Untersuchungen zur Verwendung von Klebstoffen auf der Oberfläche von Silizium-Streifen-Sensoren für die Konstruktion von Detektormodulen für das ATLAS Phase-II Upgrade vorgestellt. Drei UV-härtende Klebstoffe wurden im Vergleich zu dem derzeitigen Standard-Klebstoff an 60 ATLAS07 Miniatur-Sensoren getestet. Der Einfluss von Bestrahlung auf die chemische Zusammensetzung aller verwendeten Klebstoffe wurde unter Verwendung von Standardmethoden zur chemischen Analyse untersucht. Mithilfe der Gaschromatographie-Massenspektrometrie-Analysen von Klebstoffproben-Extrakten wurden verschiedene Ausmaße von Molekülvernetzung und gelösten Molekülbindungen festgestellt und der Grad von Strahlenhärte aller untersuchten Klebstoffe quantifiziert. Mithilfe einer Sensor-Probestation wurden die elektrischen Eigenschaften von teilweise mit Kleber bedeckten Sensoren untersucht. Im Vergleich zu Sensoren vor dem Bekleben zeigten mit Klebstoff bedeckte Sensoren einen erhöhten Leckstrom, erhöhte Zwischen-Streifen-Kapazitäten sowie Durchbrüche des Leckstroms bei niedrigeren angelegten Spannungen. Messungen der Ladungssammlungseffizienz in einem Beta-Strahlungs-Teststand wurden verwendet um den Einfluss von aufgetragenen Klebstoffen auf das Silizium-Kristallgitter zu untersuchen. Alle getesteten Sensoren - mit und ohne aufgebrachtem Klebstoff - zeigten vergleichbare Ladungssammlungseffizienzen sowie Signal-Rausch-Verhältnisse oberhalb des geforderten Minimums von zehn bei der vorhergesehenen Verarmungsspannung. Untersuchungen von Sensoren in Teststrahlmessungen zeigten außerdem, dass Sensoren um die zum Drahtbonden verwendeten Aluminiumflächen ungleichmäßig Ladung sammelten. Weiterführende Messungen konnten bestätigen, dass durch die Aluminiumflächen und darunterliegende Dotierungen das elektrische Feld innerhalb des Sensors verändert und zusätzliche Ladung um die Drahtbond-Flächen gesammelt wurde. / This thesis presents studies investigating the use of adhesives on the active area of silicon strip sensors for the construction of silicon strip detector modules for the ATLAS Phase-II Upgrade. 60 ATLAS07 miniature sensors were tested using three UV cure glues in comparison with the current baseline glue. The impact of irradiation on the chemical composition of all adhesives under investigation was studied using three standard methods for chemical analysis. Gas chromatography combined with mass spectrometry analyses of glue sample extracts showed molecule cross-linking and broken chemical bonds to different extents and allowed to quantify the radiation hardness of the adhesives under investigation. Probe station measurements were used to investigate electrical characteristics of sensors partially covered with adhesives. The presence of glue on the active sensor area was found to increase the sensor leakage current and inter-strip capacitance and frequently led to early sensor breakdowns. Charge collection efficiency measurements in a $\beta$-source setup were used to study the influence of adhesives on the silicon bulk. All sensors under investigation showed equivalent charge collection efficiencies for sensors with and without glue, as well as signal-to-noise ratios above the required minimum of ten for the foreseen bias voltage. During testbeam studies, sensor strips were found to respond inhomogeneously in bond pad regions. Follow-up measurements confirmed that the presence of bond pads affects the electric field within a sensor and leads to additional charge being collected around bond pads.

Thesis (MScAgric (Soil Science))--University of Stellenbosch, 2005. / The purpose of this study was to investigate and identify the occurrence of specific soil properties that may be important for vegetation functioning and the possible effect of the loss of or changes in these properties on rehabilitation success on the sandy coastal plains of the West Coast, South Africa. The study area covered approximately 9 400 ha on the Namaqualand coast in the vicinity of Brand-se-Baai (31º18'S 17º54'E), approximately 350 km north of Cape Town and 70 km north-west of the nearest town, Lutzville. A soil survey was done to reveal the presence of important pedological features. The 20 soil profiles surveyed are situated within six vegetation communities. Pedological features such as surface water repellency, permeable apedal subsurface horizons, subsurface impediments such as cemented (calcrete or dorbank) hardpans and significantly more clayey (cutanic, luvic) horizons were identified. A comparative study between rehabilitated and natural soils indicates that mining operations result in the formation of saline sand tailings, stripped of a large portion of the clay and organic matter fraction. The natural leaching of solutes, over a period of 25 months, is sufficient to lower salinity of the tailings to levels comparable to natural soils. This leaching can also results in lowering of soil fertility. Removal of the dorbank and the dense neocutanic horizon in the western side of the mine, loss of topographical features such as small dune systems and heuweltjies, destruction of natural soil profile morphology and the lowering of organic carbon and clay plus silt fraction can have detrimental effects on attempts at rehabilitation of this area to a natural condition similar to that which preceded the mining operation. Infiltration fingering and deep percolation results in the development of an aquifer below the reach of shallow-rooted desert shrubs. A method of water acquisition by vegetation through water distillation is investigated as a possible solution to the apparent discontinuum between the shallow root systems and deeper-lying aquifer. Volumetric water content measurements indicated that precipitation of 29.5 mm, over a period of 10 days, did not result in any variation at 235 mm, 360 mm and 900 mm depths. An average volumetric water content increase of 0.4 mm per night was measured in the first 23.5 cm of soil surface. This amount is a significant source of water that can explain the shallow root distribution. Water vapour movement due to temperature gradients can explain the diurnal volumetric water content fluctuations observed. Further studies are necessary to determine to what extent the depth of water infiltration influences the capacity of subsurface dew to provide plants with a nocturnal water source. Findings of this study can be summarised into two concepts namely: • Heuweltjies, small dune systems, and variation in depth of cemented hardpans are the main features that contribute to pedosphere variation and possibly to biodiversity. • Pedogenic features such as topsoil hydrophobicity, and cemented dorbank and dense more clayey (cutanic, luvic) subsurface horizons are important components of a soil water distillation process that could be a driving force behind vegetation functioning in this region. Mine activities result in the loss of certain pedogenic features and soil properties that that could be key ingredients to ecosystem functioning. The inability to recognise their significance and ignorance thereof when planning rehabilitation methods might prevent sustainable restoration of the environment.

The goal of this work is to develop and demonstrate a comprehensive analysis of single and multi-body composite strip-beam systems using an asymptotically-correct geometrically nonlinear theory. The comprehensiveness refers to the two distinguishing features of this work, namely the unified framework for the analysis and the inclusion of the usually ignored cross-sectional nonlinearities in thin-beam and multi-beam analyses. The first part of this work stitches together an approach to analyse generally anisotropic composite beams. Based on geometrically exact nonlinear elasticity theory, the nonlinear 3-D beam problem splits into either a linear (conventionally considered) or nonlinear (considered in this work) 2-D analysis of the beam cross-section and a nonlinear 1-D analysis along the beam reference curve. The two sub-tasks of this work (viz. nonlinear analysis of the beam cross-section and nonlinear beam analysis) are accomplished on a single platform using an object-oriented framework. First, two established nonlinear cross-sectional analyses (numerical and analytical), both based on the Variational-Asymptotic Method (VAM), are invoked. The numerical analysis is capable of treating cross-sections of arbitrary geometry and material distributions and can capture certain nonlinear effects such as the trapeze effect. The closed-form analytical analysis is restricted to thin rectangular cross-sections for generally anisotropic composites but captures ALL cross-sectional nonlinearities, and not just the well-known Brazier and trapeze effects. Second, the well-established geometrically-exact nonlinear 1-D governing equations along the beam reference curve, after being generalized to utilize the expressions for nonlinear stiffness matrix, are solved using the mixed variational finite element method. Finally, local 3-D stress, strain and displacement fields for representative sections in the beam are recovered, based on the stress resultants from the 1-D global beam analysis. This part of the work is then validated by applying it to an initially twisted cantilevered laminated composite strip under axial force. The second part is concerned with the dynamic analysis of nonlinear multi-body systems involving elastic strip-like beams made of laminated, anisotropic composite materials using an object-oriented framework. In this work, unconditionally stable time-integration schemes presenting high-frequency numerical dissipation are used to solve the ensuing governing equations. The codes developed based on such time-integration schemes are first validated with the literature for two standard test cases: non-linear spring mass oscillator and pendulum. In order to apply the comprehensive analysis code thus developed to a multi-body system, the four-bar mechanism is chosen as an example. All component bars of the mechanism have thin rectangular cross-sections and are made of fiber reinforced laminates of various types of layups. They could, in general, be pre-twisted and/or possess initial curvature, either by design or by defect. They are linked to each other by means of revolute joints. Each component of the mechanism is modeled as a beam based on the first part of this work. Results from this analysis are compared with those available in the literature, both theoretical and experimental. The margins between the linear and non-linear results are evaluated specifically due to the cross-sectional nonlinearities and shown to vary with stacking sequences. This work thus demonstrates the importance of geometrically nonlinear cross-sectional analysis of certain composite beam-based four-bar mechanisms in predicting system dynamic characteristics. To enable graphical visualization, the behavior of the four-bar mechanism is also observed by using commercial software (I-DEAS + NASTRAN + ADAMS). Finally, the component-laminate load-carrying capacity is estimated using the Tsai-Wu-Hahn failure criterion for various layups and the same criterion is used to predict the first-ply-failure and the mechanism as a whole.

In der vorliegenden Arbeit wird ein prozessübergreifendes Simulationsmodell für die Temperatur- und Gefügeentwicklung im Band und Coil beim reversierenden Warmwalzen entwickelt. In der Software werden die erstmals aufgestellten Modelle der Bandab- und aufwicklung implementiert. Die Temperatur- und Gefügeveränderungen im gewalzten Warmband werden lokal und prozessübergreifend betrachtet. Die für das gesamte Modell notwendigen Koeffizienten zur Beschreibung der Wärmeübertragung wurden mittels der inversen Methode bestimmt. Die Bestimmung der radialen Wärmeübertragung im Coil erfolgte mit Hilfe von Laboruntersuchungen in Abhängigkeit von der Temperatur, der Banddicke und des radialen Druckes. Die Validierung des Modells für die Temperatur- und Gefügeentwicklung erfolgte am Beispiel des reversierenden Warmwalzens der Magnesiumlegierung AZ31. Zu diesem Zweck wurden Versuche zu Temperaturmessungen in den einzelnen Phasen der Prozesskette durchgeführt. Die Ermittlung der Einflüsse der Umformbedingungen auf die Temperatur- und Gefügeentwicklung während des reversierenden Warmbandwalzens erfolgte abschließend mit Hilfe des entwickelten Modells. Die Ergebnisse zeigen auf, wie sich die Walzbedingungen auf die Entwicklung der Temperatur und des Gefüges auswirken.