No description available.

No description available.

This study examined if nutrient loading of phosphorus-rich pollen into small mountain lakes has a significant impact on lake productivity. Increased pollen input into lakes due to changes in vegetation (e.g., timberline advance) may increase lake production. Deteriorated pollen was recorded for frozen and freeze-dried sediment samples to determine if storage method effects pollen preservation. There were no strong relationships between pollen accumulation rates (PAR) and pigment concentrations for Sentinel Lake and Eiffel Lake. A lagged response of pigment concentrations to increased PAR was illustrated for Eiffel. Examination of pollen ratios and stomata suggests recent timberline advance for Eiffel, but pollen ratios were a poor indicator of timberline for Sentinel. Sediment storage methods did not play a significant role in differential preservation of pollen grains. Further investigation of the potential effect of PAR on lake productivity is required because timberline advance may alter lake productivity through increased pollen input. / Ecology

This investigation looked at the climatic variables affecting the durability of earth buildings and the relationship between these climatic variables and their laboratory counterparts, with the aim of providing a means whereby performance in the field under known climatic conditions can be predicted by performance in the laboratory. The investigation showed that the major climatic factors influencing the erosion of earth walls due to wind-driven rain are impacting rainfall volume, drop impact velocity (as determined by wind conditions), raindrop size and duration of rainfall. A vertical rain gauge was calibrated with climatic conditions at a test site in Sydney to enable accurate prediction of the volume of water impacting test specimens. In the laboratory, a standard spray test was modified by introducing a commercially available nozzle, which produces a turbulent spray of individual drops, rather than a stream of water. Erosion rates using this apparatus were found to vary significantly with time, and a correction formula was derived from experimental results to enable comparison to be made between field and laboratory results. Erosion rates per unit volume of water were found to be proportional to impacting velocity raised to the power 2.5 and inversely proportional to the median drop diameter raised to the power 1.2. A material factor was defined as the 60 minute erosion mass loss divided by the 60 minute volume of impacting water spray. Field tests were carried out over a period of four years and analysed in relation to the associated laboratory test results. Laboratory testing was carried out on one half of split specimens, the other half being subjected to exposure to the weather at Sydney's International Airport, with regular monitoring of wind and rain records. An empirical model was developed and was used to compare field and laboratory results. This confirmed the importance of impacting volume of water and material factor but in this case the calculated correlation between field and laboratory erosions was not improved by the addition of impact velocity and drop size terms.

No description available.

No description available.

Significant factors on steel corrosion in chloride contaminated reinforced concrete and time-to-corrosion cracking were investigated in this study. Sixty specimens were designed with seven admixed chloride contents, three concrete cover depths, two reinforcing steel bar diameters, two exposure conditions, and a typical concrete with water to cement ratio of 0.45. Corrosion current density (corrosion rate), corrosion potential, ohmic resistance of concrete and temperature were measured monthly on these specimens using both the 3LP and Gecor devices. Metal loss measurements were performed in accordance with ASTM G1-90, method C3.5, after specimens cracked. The actual corrosion weight loss of the steel reinforcing bars was then compared to the result obtained from the corrosion rate measurement devices. An interaction model for characterizing the dynamic corrosion process was developed based on the five-year corrosion database. The model demonstrates that the corrosion rate is a function of chloride content, temperature at reinforcement depth, ohmic resistance of concrete, and corrosion time after initiation. A time-to-corrosion cracking model was suggested based on a corrosion-cracking conceptual model and critical mass of corrosion products. The model predicted times to corrosion cracking are in good agreement with the observed times to corrosion cracking of the cover concrete. / Ph. D.

This thesis presents the experimental and analytical results to investigate the effect of corrosion on the mechanical properties of reinforcing bars and concrete beams, with particular reference to their ductility. In the experimental works, specimens were electrochemically corroded, before they were loaded to failure. In the finite element analysis, the corrosion of reinforcement was modelled as either internal pressure or radial expansion around corroded bars. The study indicates that the amount of corrosion to cause cracking at the bar and concrete surfaces almost linearly increased with the bar diameter and ratio of cover to diameter, respectively. No matter whether concrete cover c increased or bar distance S decreased, once the ratio of S / c became less than 2.5, corrosion cracks first propagated internally between the bars and caused delamination. Although corrosion did not alter the shape of force-extension curves substantially, it decreased bar strength and, especially, ductility greatly. Furthermore, although the reductions of strengths were identical, the ductility of bars corroded in concrete decreased more rapidly than that of bare corroded bars. Corrosion decreased beam strength and altered its ductility and failure mode. When the cracking of compressive concrete or the reduction of tensile bar area dominated beam response, corrosion increased beam ductility and caused a beam to fail in a less brittle and even ductile manner. When the deterioration of bond strength or the reduction of steel ductility controlled beam behaviour, however, corrosion decreased beam ductility and led the beam to fail in a less ductile and even brittle manner. There is a concern regarding the ductility of reinforcing bars and under-reinforced beams if the amount of corrosion exceeds 100/0, since bar ultimate strain decreased below the minimum requirements prescribed in the Model Code 90 for situations requiring high ductility.

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Although gas turbine engines are designed to use dry air as the working fluid, the great demand over the last decades for air travel at several altitudes and speeds has increased aircraft’s exposure to inclement weather conditions. Although, they are required to perform safely under the effect of various meteorological phenomena, in which air entering the engine contains water, several incidents have been reported to the aviation authorities about power loss during flight at inclement weather. It was understood that the rain ingestion into a gas turbine engine influences the performance of the engine and particular the compressor and the combustor. The effects of water ingestion on gas turbine engines are aerodynamic, thermodynamic and mechanical. These effects occur simultaneously and affect each other. Considering the above effects and the fact that they are timedependent, there are few gas turbine performance simulation tools, which take into account the water ingestion phenomenon. This study is a new research of investigating theoretically the water ingestion effects on a gas turbine performance. It focuses on the aerodynamic and mechanical effects of the phenomenon on the compressor and the combustor. The application of Computational Fluid Dynamics (CFD) is the basic methodology to examine the details of the flow in an axial compressor and how it is affected by the presence of water. The calculations of water film thickness, which is formed on the rotor blade, its motion (direction and speed) and the extra torque demand, are provided by a code created by the author using FORTRAN programming language. Considering the change in blade’s profile and the wavy characteristics of the liquid film, the compressor’s performance deterioration is calculated. The compressor and combustor’s deterioration data are imported to a gas turbine simulation code, which is upgraded to calculate overall engine’s performance deterioration. The results show a considerable alteration in engine’s performance parameters and arrive at the same conclusions with the relevant experimental observations.