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The initial fouling rate of air-saturated odourless kerosene was studied in a small scale (0.5 ins. O.D.) radiant heated horizontal tubular furnace. Two runs were carried out with the feedstock in the all liquid phase flow, fifteen during vaporization and one with all vapour phase flow. The effect of oxygen was also studied by repeating one of the vaporization runs with the relative oxygen content reduced to 15% of the saturation value. For all the runs the mass flow rate of the feedstock was held constant and corresponded to a Reynolds number of 1170 with kerosene in the liquid state at 14.7 psia and 60 °F. A complex plot of the logarithm of the initial fouling rate versus the reciprocal absolute temperature for all the air saturated runs was obtained. With increasing temperature the initial fouling rate increased in the all liquid phase flow region, decreased during the vaporization region and increased again in the all vapour phase flow region. The experimental results showed clearly that a relatively low initial fouling rate occurred close to the dryout point in vaporization. Pressure was found to have a complex effect on the fouling rate. In general however increasing the pressure caused an increase in the initial fouling rate during heating in the subcooled liquid region and during vaporization. Decreasing the oxygen content from 100% saturation to 15% saturation caused a decrease in the initial fouling rate by between three and sixty times. The critical dependence of the initial fouling rate on air or oxygen content during subcooled heating and vaporization is suggested to be due to the formation of bubbles of oxygen rich gas on the heat transfer surface. The formation of such bubbles requires the transport of oxygen to the heat transfer surface thus leading to an increase in the rate of the autoxidation fouling process. During vaporization the initial fouling rate varied circumferentially around the tube. The highest rate was obtained at the bottom of the tube where the liquid tended to flow. The lowest rate was obtained at the top of the tube where the vapour tended to flow.

NiTiHf shape memory alloys have been receiving considerable attention for high temperature and high strength applications since they could have transformation temperatures above 100 °C, shape memory effect under high stress (above 500 MPa) and superelasticity at high temperatures. Moreover, their shape memory properties can be tailored by microstructural engineering. However, NiTiHf alloys have some drawbacks such as low ductility and high work hardening in stress induced martensite transformation region. In order to overcome these limitations, studies have been focused on microstructural engineering by aging, alloying and processing. Shape memory properties and microstructure of four Ni-rich NiTiHf alloys (Ni50.3Ti29.7Hf20, Ni50.7Ti29.3Hf20, Ni51.2Ti28.8Hf20, and Ni52Ti28Hf20 (at. %)) were systematically characterized in the furnace cooled condition. H-phase precipitates were formed during furnace cooling in compositions with greater than 50.3Ni and the driving force for nucleation increased with Ni content. Alloy strength increased while recoverable strain decreased with increasing Ni content due to changes in precipitate characteristics. The effects of the heat treatments on the transformation characteristics and microstructure of the Ni-rich NiTiHf shape memory alloys have been investigated. Transformation temperatures are found to be highly annealing temperature dependent. Generation of nanosize precipitates (~20 nm in size) after three hours aging at 450 °C and 550 °C improved the strength of the material, resulting in a near perfect dimensional stability under high stress levels (> 1500 MPa) with a work output of 20–30 J cm– 3. Superelastic behavior with 4% recoverable strain was demonstrated at low and high temperatures where stress could reach to a maximum value of more than 2 GPa after three hours aging at 450 and 550 °C for alloys with Ni great than 50.3 at. %. Shape memory properties of polycrystalline Ni50.3Ti29.7Hf20 alloys were studied via thermal cycling under stress and isothermal stress cycling experiments in tension. Recoverable strain of ~5% was observed for the as-extruded samples while it was decreased to ~4% after aging due to the formation of precipitates. The aged alloys demonstrated near perfect shape memory effect under high tensile stress level of 700 MPa and perfect superelasticity at high temperatures up to 230 °C. Finally, the tensioncompression asymmetry observed in NiTiHf where recoverable tensile strain was higher than compressive strain. The shape memory properties of solutionized and aged Ni-rich Ni50.3Ti29.7Hf20 single crystals were investigated along the [001], [011], and [111] orientations in compression. [001]-oriented single crystals showed high dimensional stability under stress levels as high as 1500 MPa in both the solutionized and aged conditions, but with transformation strains of less than 2%. Perfect superelasticity with recoverable strain of more than 4% was observed for solutionized and 550 °C-3h aged single crystals along the [011] and [111] orientations, and general superelastic behavior was observed over a wide temperature range. The calculated transformation strains were higher than the experimentally observed strains since the calculated strains could not capture the formation of martensite plates with (001) compound twins.

Maritime piracy is one of the pressing global issues of the present century. The cost of piracy is human, economic, environmental and political. Recognising the piracy threat, the international community has taken several steps to address the problem. Several international organisations, including the United Nations (UN), European Union (EU) and the North Atlantic Treaty Organisation (NATO) have taken different initiatives to facilitate an international response to piracy. The UN Security Council has adopted a series of resolutions targeting piracy. As part of a military deterrence measure, the presence and coordination of international navies has been increased in high-risk piracy-affected areas, including the Gulf of Aden. However, international initiatives have proven insufficient and ineffective due to most of them primarily addressing the effects of piracy through military means. The initiatives have thus contributed only to reduce the number of attacks and their success rate, while failing to rectify the underlying reasons for piracy or solve the problems ashore in a sustainable manner. The current international framework for suppressing piracy has also been considered as insufficient to curb piracy in the sense that it does not provide any mechanism for the successful prosecution of pirates. In recent years, piracy has emerged as a growing problem in the Gulf of Guinea. The gulf has, in the past years, witnessed a sharp rise in pirate attacks. Alarmingly, both the frequency of piracy attacks and the level of physical violence against seafarers have increased in recent years. Piracy in the Gulf of Guinea has become so prevalent that it is now a growing risk for the states in the region. There are also indications of links in the area between piracy and other types of organised crime such as oil bunkering and drug trafficking. The problem has thus become a recent source of concern for the international community of nations. The states in the region lack the technical and logistical capability or the financial resources to counter the threat effectively. In addition, the limited regional integration in the maritime sphere creates further concern in this situation. In this context, there is a need for establishing enhanced cooperation at the regional level through the formulation of a comprehensive regional strategy. The thesis first outlines the international and regional framework for piracy with special emphasis on the strengths, weaknesses and possibilities of the current legal regime the United Nations Convention on the Law of the Sea (UNCLOS) and the Convention for the Suppression of Unlawful Acts against the Safety of Maritime Navigation (SUA) has been deficient in addressing the piracy problem, and focuses on some of the cooperative efforts between states in regional initiatives in Southeast Asia and East Africa, to emphasise the growing strength of regional agreements to curb piracy. Thereafter, it addresses the issue of piracy in the Gulf of Guinea by referring to its underlying causes and adverse effects, and finally evaluates the effectiveness of the current anti-piracy initiatives of the region. In doing so, it identifies the problems arising from the lack of coordination among the various organisations engaged in addressing piracy and explores the reasons for these shortcomings.