Search

Simple mean-value air-path models for modern diesel engines are in common use and have been reported in the literature. This thesis addresses several shortcomings in the models to improve the description of the cylinder charge properties during transient operation. During sudden increases in the demanded engine load, spikes are typically seen in both NOx and smoke emissions. The predicted cylinder charge properties during the transient are examined and compared with measurements of NOx and smoke. Together, the emissions data and charge properties paint a consistent picture of the phenomena occurring during the transient. Based on this analysis, alternative strategies for reducing emissions during load transients are developed. Experimental results show that spikes in both NOx and smoke can be avoided at the expense of some loss in torque response. Even if the torque response must be maintained, it is demonstrated that NOx spikes can still be eliminated. The air-path model is subsequently extended to include a throttle in the engine intake system. Based on this model, a feed-forward controller is designed to deliver the fastest possible reduction in the in-cylinder air-charge. This type of fast transient may be required to allow regeneration of Lean NOx Trap exhaust after-treatment systems. The performance of the model based controller is assessed experimentally using a completely novel sampling valve system to measure the in-cylinder gas properties on a cycle-by-cycle basis. When compared with a more conventional approach, the model based controller demonstrates a significantly faster change in the charge properties.

This thesis shows that human factors can have a large and direct impact on security, not only on the user’s satisfaction, but also on the level of security achieved in practice. The usability issues identified are also extended to include mental models and perceptions as well as traditional user interface issues. These findings were accomplished through three studies using various methodologies to best suit their aims. The research community have issued principles to better align security and usability, so it was first necessary to evaluate their effectiveness. The chosen method for achieving this was through a usability study of the most recent software specifically to use these principles. It was found that the goal of being simultaneously usable and secure was not entirely met, partially through problems identified with the software interface, but largely due to the user’s perceptions and actions whilst using the software. This makes it particularly difficult to design usable and secure software without detailed knowledge of the users attitudes and perceptions, especially if we are not to blame the user for security errors as has occurred in the past. Particular focus was given to e-mail security because it is an area in which there is a massive number of vectors for security threats, and in which it is technologically possible to negate most of these threats, yet this is not occurring. Interviews were used to gain in depth information from the user’s point of view. Data was collected from individual e-mail users from the general public, and organisations. It was found that although the literature had identified various problems with the software and process of e-mail encryption, the majority of problems identified in the interviews stemmed once again from user’s perceptions and attitudes. Use of encryption was virtually nil, although the desire to use encryption to protect privacy was strong. Remembering secure passwords was recurrently found to be problematic, so in an effort to propose a specific method of increasing their usability an empirical experiment was used to examine the memorability of passwords. Specially constructed passwords were tested for their ability to improve memorability, and therefore usability. No statistical significance in the construction patterns was found, but a memory phenomenon whereby users tend to forget their password after a specific period of non-use was discovered. The findings are discussed with reference to the fact that they all draw on a theme of responsibility to maintain good security, both from the perspective of the software developer and the end user. The term Personal Liability and General Use Evaluation (PLaGUE) is introduced to highlight the importance of considering these responsibilities and their effect on the use of security.

The cattle trade of Scotland is generally considered as a very important element of early modem Scottish economy and society. After peace was established in the Borders, and along with the gradual pacification of the Highlands, a regular trade in livestock developed over the seventeenth and eighteenth centuries, the principal component of which consisted of large-scale cattle exports to England. A number of obstacles stood in the way of the fledging industry. The credit economy was not sufficiently developed to accommodate the droving trade or to minimise the risk of dishonest dealers, bankruptcies and defaults. Also, smugglers and thieves regularly disrupted the trade, and the Privy Council repeatedly tried to curb illegal activities, especially in the Highlands. Yet, despite difficulties and regional differences, most of Scotland's territories appear to have engaged in the cattle trade. Previous research has often referred to the cattle trade. The few studies of the subject though, are either too concise to adequately explore the topic or lack the perspective of an economic history. In this thesis, wider economic factors such as the credit economy, lawlessness and Irish competition are discussed and related to price trends, export figures and general costs and profits. Present assumptions have been re-examined, and new research data has been collected and analysed along with existing evidence, in an effort to fill the gap in the secondary literature. It has been found in this thesis that both livestock trade and cattle prices followed similar trends. After decades of modest growth or stagnation in the first half of the 17th century, a market infrastructure developed by the 1660s, which allowed the cattle business to reach unprecedented levels. The growth was unevenly distributed in geographic and social terms, and was mainly accounted for by a small number of rich landowners/businessmen in the Southwest. Trade and prices stabilised to this new equilibrium for more than 80 years (with many fluctuations), until the mid-18th century when they grew significantly further.

The work presented in this thesis reports methods for microstructuring of lithium niobate. The process of light induced frustrating etching, where light from a laser is used to inhibit the etching of iron doped lithium niobate, is the subject of a detailed investigation so a better understanding of the process can be developed. The process was found to be dependent upon illumination and etch times, iron dopant levels, and irradiance levels. Analysis of the structures formed revealed that they were resistant to the etchant used and were positively charged. Two dimensional Fourier transform analysis of images obtained were used to confirm that the structures preferentially propagated along 3 directions each 120o apart. A novel electro-optically controlled domain-engineered total internal reflection switch and beam deflector is also reported. Device construction uses electric field poling of lithium niobate to create two parallel but oppositely oriented domains. When an electric field is applied across the interface between these domains a change in the refractive index of equal magnitude but of opposite sign is induced. If light incident on this interface sees a sufficient difference in refractive index it can be total internally reflected. The total internal reflection switch shows high contrast ratio switching of greater than 20dB and is less wavelength dependent than other electro-optic switches, such as the Pockels cell. The beam deflector can produce large angular deflections, which are increased by faceting of the output face. Deflections of greater than 18o have been demonstrated using this technique. Cascading of devices and possible device implementations are also suggested.

Laponite synthetic clay has been modified via exchange with "A112M7+" (M = Al, Ga, Fe or In) pillaring species and further exchanged after calcination with various metal species. The chemically tailored materials produced have been characterised using powder XRD, thermal analysis, N2 sorption at 77 K, FT-IR and MAS-NMR spectroscopies. Preliminary testing as to their suitability as deNOx catalysts has been carried out both through direct catalytic testing and in-situ FT-IR spectroscopy with NO sorbate. The pillaring species themselves were also investigated through precipitation of their sulphates and characterisation by powder XRD, as synthesised and after heating to 1150°C, thermal analysis and FT-IR and MAS-NMR spectroscopies. None of the "A112M7+ Keggin sulphates" (M = Al, Ga, Fe or In) were single phase materials, all containing the A1137+ Keggin sulphate and at least one other phase. The successful exchange and pillaring of the Laponite parent clay was demonstrated through 27Al MAS-NMR by the observation the of resonance assigned to tetrahedral AlO4. 29Si MAS-NMR showed the presence of both Q3 layer and Q2 edge Si sites and the emergence of a resonance corresponding to Q3 (1OH) Si sites upon exchange of the parent clay. Heating the exchanged material resulted in the disappearance of this resonance, but a further resonance was observed corresponding to Q4(1Al) Si sites, further confirming a successful pillaring reaction. N2 sorption at 77 K gave isotherms consistent with the presence of both micropores and mesopores and specific surface areas in the range 260 m2g-1 < SBET < 360 m2g-1, with Kelvin pore diameters between 35 and 39 A. Upon heating the exchanged clays, no major change in the specific surface area was observed up to 600 °C, with the Kelvin pore diameter reaching a maximum at 400 °C but maintaining at least its original value up to 700 °C. In-situ FT-IR spectroscopy of Co2+-exchanged "A112Fe7+" Laponite in the presence of NO revealed a number of surface species (most notably nitrates, N2O and NO2) and suggestions have been made as to their route of formation. Catalytic testing of a range of materials for N2O destruction in both the presence and absence of CH4 showed a number to achieve 100 % conversion at low reactant flow rates, with the V-exchanged A1137+ Laponite showing the highest potential as a deN2O catalyst.