My dissertation research consists of two themes: (a) the analysis of Middle Jurassic - Early Cretaceous marine magnetic anomalies (M-anomalies) in order to construct a comprehensive geomagnetic polarity timescale and (b) the investigation of the upper oceanic crustal architecture using downhole geophysical logs. These themes were chosen to better understand how remotely-sensed geophysical signals elucidate the formation and evolution of oceanic crust. This revised Pacific-wide MGPTS model shows significant improvement in its reliability, exhibits global applicability, and highlights changes in the paleo-Pacific spreading regime. By integrating Atlantic Manomaly analyses with the new MGPTS model and reviewing previous seismic studies, we shed new light on the causes of a ubiquitously distributed ?Atlantic anomaly smooth zone? where little coherency among M5-M15 anomaly sequence is observed. For the second theme, I analyzed the architecture of 15 m.y. old superfast spreading East Pacific Rise crust drilled at Ocean Drilling Program Hole 1256D in the eastern Pacific. An intact upper oceanic crustal section was penetrated at this site to a depth of 1507 mbsf. In situ crustal architecture was mapped from resistivity imagery (electrofacies by Formation MicroScanner) combined with recovered cores and other logs. Highlights of this research are: (1) most of the extrusive section consists of massive flows and fragmented formations including breccias, which has important implications for the magnetic source layer and pathways of hydrothermal alteration; (2) the dike complex is composed of sheeted-dikes dipping away from the paleo-spreading axis consistent with submersible observations at other sites in the eastern Pacific; (3) the crustal construction processess from ridge axis to abyssal plain during 0-50 kyr time are consistent with previous seismic reflection studies based on the integration of our stratigraphy model with lava flow observations from the southern East Pacific Rise.

In an effort to achieve lighter and more economical space structures, a new patented steel composite member has been suggested and used in the construction of some steel roof structures. This special element has a sandwich construction composed of some strips of steel plates placed longitudinally along a helical wire core. The function of the helical core is to transfer the shear between the flange plates and increase the sectional inertia of the resulting composite member by keeping the flange plates at a desired distance from each other. Because of the lack of research, design engineers usually treat such elements as a solid member as if it has a full shear transfer between the flanges. However, a detailed analysis shows that this is not a valid assumption and leads to very unsafe results. In this context, the purpose of this study is to investigate the behavior of such members under axial compression and determine their effective sectional flexural rigidity by taking into account the shear deformations. This study applies an analytical investigation to a specific form of such elements with four flange plates placed symmetrically around a helical wire core. Five independent parameters of such a member are selected for this purpose. These are the spiral core and core wire diameters, the pitch of the spiral core, and the flange plate dimensions. Elements with varying combinations of the selected parameters are first analyzed in detail by finite element method, and some design charts are generated for the determination of the effective sectional properties to be used in the structural analysis and the buckling loads. For this purpose, an alternative closed-form approximate analytical solution is also suggested.

This thesis covers database creation, system design and application development for wire line telecom infrastructure within Geographical Information Systems (GIS) and concentrates on spatial decision support applications and serving wire line subscriber coordinates for emergency calls in Ankara. The main mission of the Telecommunication in the past was to serve for voice communication activities. Currently voice, internet, data and video communications are available. These new services need better bandwidth capacity and/or renewal of infrastructure with Fiber Optical cables. Telecom has a complex wire line infrastructure, both in physical and logical topology. It is important to manage this complex infrastructure to give better services with new installation and update activities. Due to these requirements Telecom infrastructure needs to be managed with GIS, which visually provide physical and logical relationships. In this study it&rsquo / s aimed to build a GIS system for Turk Telekom (TT) including digitization of wire line cable infrastructure, geocoding subscribers and serving the coordinates of subscribers. The data layers are stored in Oracle Spatial Data Option (SDO) and spatial data information is kept in MapInfo MapCatalog. The data schemes for 81 provinces are created. The applications are developed with Borland Delphi version 7 and Microsoft Visual Studio 2008 .NET Framework. There are several GIS applications developed so far for the infrastructure of TT, since TT needs to know the location and quality of the infrastructure already present in the field and needs spatially to decide on areas that need maintenance including improvement, replacement, and new installations to improve the service. This study is presented as an alternative spatial decision support system for the improvement of the current infrastructure and services given to the customers, by using digitized network and geocoded subscriber data that is stored in GIS system. This study is carried out with customer participation and on site development with Telecom staff.

The Texas Department of Transportation (TxDOT) has completed the design of a signature bridge in Fort Worth, TX. The proposed structure is comprised of precast, post-tensioned concrete network arches. The arches will be cast on their sides and then rotated into the vertical orientation. Concerns exist about the durability and stability of the arches during stressing, handling, and transportation. The rotation process in particular represents a critical period in the life of the arches. A monitoring system was proposed to track stresses in the arches throughout the construction operations. The primary goals of the project are to install vibrating wire gages (VWGs) in the arches prior to casting to monitor the performance of the arches until the bridge is completed. The instrumentation will be used to provide real-time feedback to TxDOT and the contractor during stressing, handling, and bridge construction. This thesis focuses on the results of a preliminary laboratory study conducted in support of the instrumentation initiative. The purpose of the study was two-fold: to establish the capabilities and limitations of the VWGs and to study the buckling behavior of slender concrete elements with unbonded post-tensioning. More than sixty axial load tests were performed on two slender concrete specimens instrumented with VWGs. Observations are made on the accuracy and reliability of the VWGs. In general, the VWGs were found to be both accurate and reliable in measuring structural parameters and reporting trends in behavior, even at low loads. Some apparent errors were identified, but these were attributed to testing inconsistencies and scale factors rather than to gage error. Observations were also made on the buckling behavior of the elements under a variety of axial loading configurations. The effects of the engagement of the tensioned strand with the duct had a significant impact on the behavior. Strand engagement was shown to increase the buckling capacity of the members through stiffening action, but did not necessarily eliminate the risk of instability. Both the gage resolution study and the stability tests are expected to significantly enhance the ability of the research team to support the arch construction operations. / text

Shape Memory Alloy is an amazing material, which can “remember” and return to its original shape when heated due to its temperature dependent phase transformation. Shape Memory Alloy wire has significant potential for application in the automobile industry due to its high ratio of energy / weight and silent actuation. However, a dependable method to measure the operating temperature of SMA wire and a reliable heat transfer model to characterize the dynamics of the SMA wire limit its widespread use in the automobile industry. This thesis presents a detailed description of the work performed to develop a reliable method for determining surface temperature of current carrying SMA wires and the development of a heat transfer correlation for natural convection cooling of heated SMA wires. The major findings of the research are as follows: When a spot welded thermocouple measures the temperature of a current carrying SMA wire, there is a “spurious voltage” ΔV added to the thermo electro-motive force (EMF) of the thermocouple as a result of a voltage drop across the two points of contact that the thermocouple wires make with the SMA wire. This leads to an erroneous temperature reading that can be higher or lower than the actual temperature depending on the direction of current flow. When the carrying current is reversed in direction, the “spurious voltage” becomes –ΔV allowing a correct temperature reading to be obtained by averaging the readings based on opposed current flow. A two-step spot welding procedure for attaching thermocouples to SMA wire can eliminate the influence of the “spurious voltage” in the temperature reading. By spot welding the thermocouple wires onto the SMA wire one by one, the thermocouple lead offset is eliminated and the thermocouple provides an accurate point source reading. Infrared thermal imaging can be a good supplement in the experiment to monitor errors in temperature readings from thermocouples. Due to the curvature of the SMA wire, the temperatures of the locations on the SMA wire that are the closest to the infrared camera represent the temperature of the SMA wire. So a line analysis across the SMA wire on the software “ThermaCAM” is required to determine the temperature of the SMA wire by infrared thermal imaging and the highest temperature on the line is the temperature of the SMA wire. A new natural convective heat transfer correlation comprising the inclination angle φ is developed based on experimental results, which can be used to predict the temperature of a SMA wire given its diameter and inclination angle. The comparisons show that the new correlation agrees with existing correlations in a vertical orientation and for small Rayleigh numbers (0.001 < RaD < 0.05) in the horizontal orientation. The correlation developed in this work for horizontal orientation tends to overestimate values of Nusselt numbers as predicted in other correlations when the Rayleigh number is high (0.05 < RaD < 0.6). It is speculated that this overestimation can be attributed to a temperature distortion associated with thermocouple measurement at or near ambient pressure conditions.

<p>This study reports on the changes in the structural properties of a tungsten-filament when exposed to a methane / hydrogen ambient for different durations at various filament-temperatures.</p>

<p>The overall aim of this project is to study the heat transfer inside the reaction chamber of the Hot-Wire Chemical Vapor Deposition (HWCVD) system with a commercial software package FLUENT6.3 / it is one of the most popular Computational Fluid Dynamics solvers for complex flows ranging from incompressible to mildly compressible to even highly compressible flows. The wealth of physical models in FLUENT allows us to accurately predict laminar and turbulent flows, various modes of heat transfer, chemical reactions, multiphase flows and other phenomena with complete mesh flexibility and solution-based mesh adaptation. In this study the 3-D HWCVD geometry was measured and created in GAMBIT which then generates a mesh model of the reaction chamber for the calculation in FLUENT. The gas flow in this study was characterized as the steady and incompressible fluid flow due to the small Mach number and assumptions made to simplify the complexity of the physical geometry. This thesis illustrates the setups and solutions of the 3-D geometry and the chemically reacting laminar and turbulent gas flow, wall surface reaction and heat transfer in the HWCVD deposition chamber.</p>

<p>When the amorphous silicon (a-Si) dangling bonds are bonded to hydrogen the concentration of the dangling bond is decreased. The resulting film is called hydrogenated amorphous silicon (a-Si:H). The reduction in the dangling bonds concentration improves the optoelectrical properties of the film. The improved properties of a-Si:H makes it possible to manufacture electronic devices including a solar cell. A solar cell device based on the hydrogenated amorphous silicon (a-Si:H) was fabricated using the Hot-Wire Chemical Vapour Deposition (HWCVD). When an n-i-p solar cell configuration is grown, the norm is that the p-doped layer is deposited from a mixture of silane (SiH4) gas with diborane (B2H6). The boron atoms from diborane bonds to the silicon atoms and because of the number of the valance electrons, the grown film becomes a p-type film. Aluminium is a group 3B element and has the same valence electrons as boron, hence it will also produce a p-type film when it bonds with silicon. In this study the p-doped layer is grown from the co-deposition of a-Si:H from SiH4 with aluminium evaporation resulting in a crystallized, p-doped thin film. When this thin film is used in the n-i-p cell configuration, the device shows photo-voltaic activity. The intrinsic layer and the n-type layers for the solar cell were grown from SiH4 gas and Phosphine (PH3) gas diluted in SiH4 respectively. The individual layers of the solar cell device were characterized for both their optical and electrical properties. This was done using a variety of experimental techniques. The analyzed results from the characterization techniques showed the films to be of device quality standard. The analysed results of the ptype layer grown from aluminium showed the film to be successfully crystallized and doped. A fully functional solar cell was fabricated from these layers and the cell showed photovoltaic activity.<br /> &nbsp / </p>

The longitudinal fluctuations at a point in the core of air flowing through a 15 cm. diameter pipe at a mean centerline velocity of 13.4 and 29.5 m/sec. were measured with a hot-wire anemometer. This signal, after analog to digital conversion, was stored in the form of digital samples on an ICT computer drum storage device. This method of data recording includes the effect of all eddy frequencies from DC upwards and the presence of large, slow eddies in the longitudinal direction became apparent in the subsequent autocorrelations. The longitudinal dispersion of a tracer material injected on the axis of the pipe was measured over short distances with pulses of approx. 20 msecs. duration of radioactive Krypton-85, detected at two downstream stations by small surface-barrier radiation detectors. By varying the separation of these two stations, an asymptotic mixing coefficient was established which was very much greater than the corresponding transverse mixing coefficient measured by other workers. The method proposed by Philip (4) for the prediction of the Lagrangian time autocorrelation from the Eulerian velocity measurements was examined with the correlation data of Baldwin and the data obtained in this investigation. The method applied to the unfiltered correlation data in the present measurements in a non-isotropic field to predict a longitudinal turbulent Peclet no. was found to predict a value in the region measured experimentally. When the present velocity data was filtered to remove the low-frequency components and give a turbulence intensity equal to that measured in a radial direction in previous dispersion measurements, the mixing coefficient predicted with Philip's method was found to agree very well with the transverse mixing coefficient reported in these investigations. A value is also suggested for the longitudinal Peclet number in the absence of the low frequency fluctuations. / Thesis (Ph.D.)-University of Natal, Durban, 1970.

Syftet med undersökningen är att analysera varifrån nyheterna har sitt ursprung och hur återanvändandet av nyheter ser ut i fyra av de största riksmedierna under en arbetsvecka. De fyra medier som ingår i undersökningen är Svenska Dagbladet, Dagens Nyheter, Sveriges Televisions Rapport och Sveriges Radios Ekot. I undersökningen ingår 356 analysenheter och det är en kvantitativ undersökning. För att förstå och analysera resultatet har teorierna gatekeeping, mediernas kommersialisering och nyhetsvärdering använts. Undersökningens resultat visade bland annat att 27 procent av analysenheterna består av köpt eller kopierat material från nyhetsbyråer eller material som är omskrivet från andra medier. Undersökningen visar också att det är stora skillnader mellan olika medietyper. Den största andelen material från nyhetsbyråer kom från tidningarna Dagens Nyheter och Svenska Dagbladet (såväl procentuellt som i absoluta tal). Både Ekot och Rapport hade en betydligt lägre frekvens byråmaterial som de hänvisade till. Såväl radio- som tv-materialet är det ofta svårt att hitta ursprunget till, därför faller mycket material under ”går ej att avgöra”.