A Comprehensive Predictive Corrosion Model incorporating varying Environmental Gas Pollutants applied to Wider Steel Applications

A comprehensive model has been developed to predict uniform corrosion rate of structural steel under the effect of low pH conditions for example acid rain. Acid rain is mainly caused by emissions of sulfur dioxide (SO2) which reacts with the water droplets in atmosphere to produce acidic solution which is the primary cause of corrosion of steel structures such as bridges, and weathering of stone buildings and statues. A five-stage division was applied to mathematically describe the model as: (i) the growth rate of air-suspended water droplets (i.e. moisture) depending on the condensation/evaporation rate, (ii) the absorption of gas phase SO2 in the droplets forming bisulfite HSO_3^- ions, (iii) the coalescence of these SO2 absorbed water droplets under the effects of wind speed and gravity, (iv) the deposition rate of SO2 absorbed droplets on steel substrate depending on the inclination and azimuth angles of steel surfaces and, (v) the corrosion rate of steel due to the deposition of these SO2 absorbed droplets. The incorporation of all the above stages develops a comprehensive corrosion prediction model which not only includes the electrochemical parameters but also large number of physical, environmental and material parameters. Experiment was performed to analyse the corrosion rate of steel samples by exposing them to moist SO2 corrosion test. A comparative analysis between the model predictions and experimental results was performed to verify the reliability of model. The predictive trends of corrosion rate of steel were also generated for different values of temperature, relative humidity, and SO2 mole percentage

Optimizing flame synthesis of carbon nanotubes: experimental and modelling perspectives

Synthesis of carbon nanotubes in flames has become highly attractive due to its rapid, inexpensive, and simple method of production. The study of flame synthesis of carbon nanotubes revolves around the control of flame and catalyst parameters to increase the synthesis efficiency and to produce high quality nanotubes. The control parameters include flame temperature, concentration of carbon source species, catalyst type, equivalence ratio, and fuel type. Carbon nanotubes which are produced with rapid growth rate and possess high degree of purity and alignment are often desired. The present study reviews various optimization techniques from the advanced studies of chemical vapour deposition which are applicable for the synthesis of nanotubes in flames. The water-assisted and catalyst free synthesis are seen as possible candidates to improve the growth rate, alignment, and purity of the synthesized nanotubes. The state-of-the-art of the flame synthesis modelling at particle and flame scales are reviewed. Based on the thorough review of the recent experimental findings related to the catalytic growth of nanotube, possible refinement of the existing particle scale model is discussed. The possibility of two-way coupling between the two scales in computational fluid dynamics may be a major contribution towards the optimization of the flame synthesis

Integrated Environmental Modelling Framework for Cumulative Effects Assessment

Global warming and population growth have resulted in an increase in the intensity of natural and anthropogenic stressors. Investigating the complex nature of environmental problems requires the integration of different environmental processes across major components of the environment, including water, climate, ecology, air, and land. Cumulative effects assessment (CEA) not only includes analyzing and modeling environmental changes, but also supports planning alternatives that promote environmental monitoring and management. Disjointed and narrowly focused environmental management approaches have proved dissatisfactory. The adoption of integrated modelling approaches has sparked interests in the development of frameworks which may be used to investigate the processes of individual environmental component and the ways they interact with each other. Integrated modelling systems and frameworks are often the only way to take into account the important environmental processes and interactions, relevant spatial and temporal scales, and feedback mechanisms of complex systems for CEA. This book examines the ways in which interactions and relationships between environmental components are understood, paying special attention to climate, land, water quantity and quality, and both anthropogenic and natural stressors. It reviews modelling approaches for each component and reviews existing integrated modelling systems for CEA. Finally, it proposes an integrated modelling framework and provides perspectives on future research avenues for cumulative effects assessment

Hydrogen sensing using palladium coated long period gratings

The use of palladium coated optical fibres containing an in-fibre long period grating (LPG) structure for the sensing of low concentrations of hydrogen has been investigated. Previous proof of principle experiments were refined and extended, demonstrating sensitivities of up to 60 pm for 1% hydrogen at an operating temperature of 70°C. Characterisation of the Pd deposition technique (RF sputter coating) including XPS and SEM analysis to investigate surface roughness and contamination were carried out and are discussed. These measurements were prompted by the need to characterise and eliminate sensor drift associated with delamination of the sensor layer. Particular care was taken to characterise the optical properties of Pd thin films, both in the presence of hydrogen and without, through ellipsometry and surface plasmon resonance, since values gained from the literature showed wide variations. The results presented in this thesis differ from published Pd refractive indices but are specific for the conditions used in this work. Techniques to directly measure the refractive index profile within the core of an LPG were investigated and a possible solution is presented. Theoretical models to calculate the transmission spectrum of a LPG, both with and without a Pd layer are presented, discussed and the implications due to the poor characterisation of the LPG are considered. The potential use of higher order double cladding modes (with up to 20 times the sensitivity of the lower mode orders) as a sensing regime is investigated and the practical limitations discussed

An experimental investigation of spray combustion in a two stage system

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