Search

This thesis aims to reduce the costs associated with optimising a part, process, and tool design in order to avoid defects when using the thermoplastic stamp forming process. This was done by investigating the defects that can occur when using the process, the mechanisms by which they occur, and how they can be avoided. This knowledge can then be used to avoid defects in other designs, hence reducing design optimisation costs. This work focuses on an omega geometry that was stamp formed from a carbon fibre PEEK laminate in a series of manufacturing trials. Wrinkling, corner thinning, edge squeeze out, and fibre breakage defects were observed in the trials. Hypothetical mechanisms that caused these defects were proposed, and design feature modifications that prevented each of them were identified. However, the modification that prevented wrinkling caused fibre breakage, so an optimum design that prevented both wrinkling and fibre breakage was not tested. However, this optimum design was proposed based on the hypothetical defect mechanisms. The use of process simulation was also investigated as this has the potential to reduce design optimisation costs by predicting whether defects will occur in a given design. A forming simulation was conducted for three of the designs tested in the trials, and for the proposed optimum design. A verification and validation process was conducted in order to establish and improve the credibility of the simulations. It was initially found that there was uncertainty in the defect predictions due to the use of fibre stress to indicate defects. However, this uncertainty was reduced by using basic methods that accounted for the compaction and temperature reduction of the material. The fact that the defects were predicted with reasonably low error and uncertainty suggested that the models used in the simulations could be used to predict defects in similar designs.

A good understanding of the physical properties of explosives is essential for their safe and efficient usage. Numerical simulations have proven to be an excellent tool with which to develop and verify models which describe both ignition and detonation of explosives. The objective of this work is to improve the robustness and accuracy of numerical simulations of both ideal and non-ideal explosives. Much of the complexity of the detonation phenomenon arises due to the finite width of the reaction zone, which causes the properties of the detonation wave to deviate from the predictions of the ZND model. If numerical models are to predict the attributes of the explosive to greater accuracy, then the dynamics of the reaction zone must be adequately resolved. This thesis also reviews the scientific literature in order to contextualise the developments presented here. The approach taken in this thesis is to describe the thermodynamics in the reaction zone as a mixture of reactants and products which exist at pressure and thermal equilibrium. To this end, mechanical equations of state of Mie-Gr\"{u}neisen form are developed with extensions, which allow the temperature to be evaluated appropriately, and the temperature equilibrium condition to be applied robustly. Furthermore the snow plow model is used to capture the effect of porosity. The methodology is applied to predict the velocity of compliantly confined detonation waves. Once reaction rates are calibrated for unconfined detonation velocities, simulations of confined rate sticks and slabs are performed, and the experimental detonation velocities are matched without further parameter alteration, demonstrating the predictive capability of our simulations. We apply the same methodology to both the non-ideal explosive EM120D (an ANE or ammonium nitrate based emulsion) and the comparatively ideal TATB based explosive PBX 9502. Furthermore, this thesis presents a novel methodology to use gauge data from shock initiation experiments to calculate values for the reaction rate. The methodology can be applied to determine rate law parameters without the use of computationally intensive hydrocode simulations. The validity and limitations of this approach are demonstrated through its application to simulated gauge data for an idealized explosive. The resulting rate law is then used in simulations of shock to detonation transition, and confined detonation waves of the TATB based explosive PBX 9502. Comparison of the results with experimental data is favourable.

This thesis describes the characterisation of human MRCKcc (myotonic dystrophy kinase-related Cdc42-binding kinase) and the signalling role of MRCK in tumour cell invasion. The first results chapter reports the identity and sequence of the human isoform of MRCKa. It is shown that previously reported expression of a sequence known as PK428 in breast tumours with poor prognosis represents MRCKa expression. PK428 is identified as a partial cDNA of the previously uncloned human MRCKa. The cloning of several splice-variants of full-length MRCKa is described. MRCKa expression is also analysed in human tumour samples, but the data are not conclusive enough to establish MRCKa expression as a prognostic marker. Subsequent work details the functional role of MRCKa and MRCK? in mediating invasion of three-dimensional extracellular matrices by tumour cell lines. In tumour cells that exhibit an elongated morphology, abrogation of signalling of both MRCKa/?, by RNA interference, and ROCK (Rhokinase), with the small-molecule inhibitors Y-27632 or HA-1077, results in inhibition of invasion. This is associated with a collapsed cellular morphology and abrogation of phosphorylation of both the myosin targeting subunit (MYPT1) of myosin light chain phosphatase and of myosin light chain (MLC2). Effects on morphology and invasion are recapitulated with blebbistatin, a specific inhibitor of actomyosin contractility. This suggests that MRCK and ROCK have a redundant role in promoting invasion through regulation of myosin activity. In a cell line with a rounded morphology in threedimensional matrices, switching between three morphological states is identified - rounded, elongated and collapsed, in order of decreasing actomyosin contractility. In this cell line, MRCK and ROCK have a redundant role in maintaining the elongated morphology but ROCK alone signals the high level of contractility that drives the rounded morphology.

This thesis investigates the usability of an 800 page textbook compared with a hypertext version containing the same information. Hypertext is an interesting new medium in that it is seen as possessing advantages as both delivery technology that influence cost and access to information and design technology influencing student achievement. Unfortunately the proclamations of its advocates have usually exceeded empirical findings. Also, rapid advances in both hardware and software are necessitating the frequent re-evaluation of contemporary hypertext. In addition to an up-to-date evaluation of the relative performance of book and hypertext supporting set tasks, the research reported in this thesis also sought to specifically analyse the potential role individual differences could play within media evaluation. To do this the cognitive styles and spatial ability of 57 postgraduate student volunteers, from two computer related diplomas, were measured. Half the subjects were then randomly assigned to a Book group and half to a Hypertext group. Each group was then allocated the same amount of time to complete two separate tasks: 1) short answer questions analysing the basic information retrieval potential of each medium, and one week later 2) four open-ended short essay questions. Surprisingly, subjects assigned to the Book group performed significantly better than those assigned to the Hypertext group for Task 1. The mean academic performance of subjects (the mean mark obtained over the 8 modules of their diploma) predicted most variance in Task 1 performance for both groups. However, with Task 2, the cognitively more demanding exercise, none of the measured individual differences could significantly predict the scores of subjects. Another surprising finding, given that all subjects were studying computing, was that the amount of prior computing experience was found to approach significance for those subjects assigned to Hypertext for Task 1. Given the ease with which this particular individual difference could be manipulated it was decided to run a second experiment employing -subjects with more experience of the Hypertext system used. The results from this second cohort showed no significant differences in score for either task between Book or Hypertext. However, as the more qualitative data from a questionnaire showed, there are a large number of different factors and issues that contribute to the ultimate acceptability of one medium compared with the other. The thesis concludes by recommending a number of possible avenues for future research looking at the role hypertext has to play in the construction of hyperlibraries and Virtual Learning Environments.

The use of immobilized Chiorella ernersonii for the removal of inorganic mercury from aqueous solution in batch and continuous-flow processes was inyestigated. Initial experiments showed that HgCl2 added to growth mediun. at I mgg -I r did not markedly affect the growth of non-immobilized Chiorella at io cell ml. Batch culture experiments using 203 Hg showed that whilst mercury was removed from medium and accumulated by alginate-immobilized and non-immobilized Clzlorella, a considerable amount of mercury was lost by volatilization. Inunobilized cells accumulated significantly more mercury than non-immobilized cells at higher inoculum densities, probably due to greater growth of immobilized cells. Living cells accumulated significantly more mercury than heat-killed cells, though mercury volatilization was greater with killed cells, indicating that the mechanism of volatilization was nonenzymic. Calcium alginate caused mercury volatilization, probably due to a chemical factor capable of transforming mercury to a more volatile form. Continuous-flow studies using packed-bed reactors showed that unstocked agarose exhibited less mercury volatitlization than alginate. Mercury removal efficiency from medium containing 1 mg Hg r by alginate- and agarose-i;nniobilized Ciziorella during 15-day experiments was over 90% with higher inoculum densities. Considerable cell leakage into effluent was measured. With agarose-immobilized cells, the use of high flow rates reduced mercury removal efficiency whilst lower flow rates. effluent recycling or extended operation times increased volatilization. Scanning electron microscopy showed that cells were mainly pisent at the periphery of immobilized-cell beads in packed-bed reactors, and this may have contributed to cell leakage. A mercury-resistant alga, isolated from the Trent-and-Mersey Canal, accumulated and volatilized mercury, suggesting that mercury volatilization may be a common mechanism of mercury resistance amongst microalgae. Immobilized living cells were considered less suitable for mercury removal than dead cells immobilized in matrices with good mechanical strength.