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The dynamic performance of a turbocharged diesel engine during transient operation has been studied. For appropriate analysis of data obtained from engine transient operation, four alternative automated filtering methods were implemented on the cycle-by-cycle in-cylinder pressure. The techniques to process instantaneous emission data and align the transient data from different analyzers were developed. In the experimental study, the effects of engine speed and EGR have been investigated through load increase tests at a constant engine speed with different EGR calibrations. Based on the experimental results, a real-time diesel engine model was developed by Simulink. The model is capable of simulating the main engine parameters. It included the air path model, combustion model and dynamic emission behavior model. The model can run as a real-time simulator for engine control strategy development. . An advanced fast predictive control approach was proposed and validated in a HIL simulation platform. The model predictive control was developed for EGR and VGT control. The oxygen concentration oriented control was designed and implemented in the real-time model. Compared with PID control, MPC presents a good tracking performance of reference values with a shorter response time. The results in HIL proved the real-time capability of the control strategy.

Human respiratory syncytial virus is a leading cause of lower respiratory tract infection in infants. Current prophylaxis with Palivizumab, a humanised anti-fusion glycoprotein monoclonal antibody, has only achieved moderate success. In animal models, immunization with G glycoprotein has led to largely genotype specific immunity. This suggests the hypothesis that anti-G antibodies to the infecting virus genotype, either acquired transplacentally or induced by immunisation, may contribute to protection of the infant in the early months of life. The aim of this study has been to test this hypothesis by measuring levels of maternally acquired antibody to the G glycoprotein of the infecting virus genotype in an index group of infants with severe HRSV infection and, to the same genotype, in a comparison group of infants with no history of HRSV infection. As only 2% of infants suffer severe disease on primary HRSV infection, the comparison group are assumed to be destined to be resistant to severe infection. A deficiency of anti-G antibodies in the index group will thus indicate a protective role for these antibodies. A phylogenetic study was carried out in Newcastle upon Tyne from autumn 2007 to spring 2010 revealing three circulating genotypes of HRSV, namely GA2, GA5 and BA4 although GA5 was not detected in the third epidemic. The G genes of GA2 and BA4 and the F gene of GA2 were cloned and expressed individually in modified vaccinia Ankara virus. The recombinant proteins were used in the development of a concanavalinA capture ELISA sufficiently sensitive to detect maternal antibodies in the acute sera of infants under 6 months of age. An attempt was made to refine the assay in order to separately detect antibodies to the conserved and variable epitopes of the G glycoprotein. However, mapping of conserved and variable epitopes revealed overlap epitopes precluding the development of a differentiation in a simple ELISA assay. An index group of infants with severe HRSV infection and a comparison group of infants of similar age with no history of HRSV infection were recruited with consent by their legal carer during the epidemic of 2009/2010. The infecting virus lineage of each infant in the index group, either GA2 or BA4, was identified by reverse transciptasepolymerase chain reaction of virus recovered from nasal secretions. Sera were collected from both groups, at the acute stage of infection for the index group, and screened for ii HRSV specific IgA by ELISA. Only those without detectable IgA were included in the study. IgG maternal antibodies to the recombinant G glycoprotein of the infecting virus genotype and the F glycoprotein of the GA2 genotype were measured in the sera of index and comparison group infants whilst maternal antibody levels to both F and G glycoproteins in the sera of both index and control sera decayed at similar rates with age, the index group possessed significantly more anti-G and anti-F antibody at all ages suggesting that infants hospitalized with severe HRSV infection were not deficient in antibodies to either glycoprotein contrary to the hypothesis under test. However, mean maternal antibody levels at birth have been shown to fall across the winter epidemic and the above analysis may be susceptible to bias introduced by uneven sampling of infants across the epidemic. To avoid this potential error, anti-F/anti-G antibody ratios, which give a measure of anti-G immunity independent of age and time of collection, were also compared in the sera of index and comparison group infants. Mean ratios were not significantly different between the two groups also rejecting the hypothesis that severely affected infants have a deficiency in maternal anti-G antibodies. These studies, therefore, fail to establish a role for anti-G glycoprotein antibodies in the protection of infants against severe lower respiratory tract disease.

Out-of-plane welding distortion has been a persistent problem in welding industries. In order to find solutions for such a problem, substantial experimental and computer modelling work on residual stresses and out-of-plane distortion analysis need to be carried out. Such computer modelling requires the temperature fields or histories during welding as pre-requisite input which can be obtained either from actual measurement or computer simulation. The object of this thesis is to develop computational techniques which can be used to compute these temperatures. Experimental work on temperature measurement has also been carried out to provide data for the purposes of validating the computer models. A data acquisition system was successfully calibrated and used to record temperature histories of the plate during the welding process. Four experiments were carried out by joining rectangular plates of size 500 min by 250 min together with "V" weld-preparation configuration at various thicknesses. Thermocouples were affixed to the top and bottom surfaces of the specimen at locations just within or very near to the heat affected zone and at locations remote from the heat affected zone to record the temperature history during welding and cooling. Related analytical theories were studied and used to validate the finite element models. The method of superposing the effects of a number of instantaneous plane heat sources to the plates has been investigated and used successfully for the evaluation of the temperature history of the plates where the heat input varies with time. Finally, a computational technique to simulate the temperature history near to and remote from the heat source was successfully developed using ANSYS 8.0 finite element software and applied to three-dimensional transient models, three-dimensional steady state models and two-dimensional transient sectional models. All the simulated results were in good agreement with experimental measurements.

This thesis addresses three aspects of frequency estimation. First, the problem of accurately estimating frequencies in a multi-tonal signal is discussed with references to many techniques used today. Particularly, frequency estimation methods such as fast Fourier transform (FFT), Multiple Signal Classification (MUSIC), Quinn and Fernandes (Q&F) and a proposed frequency estimation approach called Optimal Frequency Estimation (OFE) are elaborated. This latter technique is proposed as a way to increase the estimation accuracy of tonal frequency components in a complex signal with limited data length. OFE is compared with FFT, MUSIC, a popular multi-tonal frequency estimation method, and the recent Q&F method. Signals with added Gaussian noise are used to investigate its estimation accuracy and variance empirically. The technique is shown to perform well on simulation data. Results demonstrate its superiority in estimating frequencies at signal to noise ratio from 24dB and above. Its computational effort in estimating frequencies is also shown to be efficient as OFE is based on gradient free convergence. Next, OFE is applied to a single input single output (SISO) control system developed recently to investigate its influence. The controller uses online plant estimation and it is extended to multiple input multiple output (MIMO) systems. The online plant estimation and control attenuates unknown disturbance tones through continuous tuning. A stability criterion is derived to demonstrate the need for accurate frequency estimation in the control scheme. The performance of the control algorithm OFE is investigated by computer simulation using an air duct system as an example. Results show that accurate frequency estimation is essential for a successful and stable attenuation. Finally, three hardware test rigs are designed to realize the above schemes for practical digital signal processing (DSP) laboratory experiments. Active sound control is studied on a microphone-speaker array for the SISO case. A novel satellite plate test rig is used to investigate micro-vibrations on board a spacecraft. An L-shaped enclosure modelled after a commercial compressor is constructed with shakers and accelerometers mounted for MIMO control. In conclusion, future work and implementation under more general cases are outlined.

The aim of this thesis is to investigate and understand the issues involved in using multicast communications over a non-reliable satellite link and to suggest suitable methods to improve multicast services when used on packet networks. Point-to-multipoint communications have been used for distribution of data. These are mainly found on circuit switched networks where there is bandwidth allocation, ensuring a good transmission link. However, as packet switched networks become more evolved due to their interesting properties of being able to share the available bandwidth, multicast communication is increasingly employed. A satellite link in a packet network is often used to provide connection to remotely located hosts. To use point-to-multipoint communications, especially for real-time applications, across a satellite link, a scheme employing Forward Error Correction (FEC) is presented. The scheme uses an XOR (Exclusive-OR) coding technique to generate the redundancy. It adjusts the rate of coding according to the varying condition of the link. By using this transmission strategy, the proposed scheme is implemented at the transport and the data link layer to enhance multicast communication services. In recent years, there has been a tremendous growth in the number of local and wide area networks. To manage these networks, it is necessary to monitor and analyse the network traffic regularly. Many commercially available analysers are either too expensive or too complicated. Perhaps the greatest setback lies in their presentation of vital information to the users in the form of screen after screen of textual data. Thus, it may require someone of experience to be able to fully understand the situation on the network and this, only after a detailed study of the data. The thesis investigates and proposes a new method of processing and presenting the information that will enhance the flexibility and productivity in the process of network troubleshooting.

The occurrence of hexavalent chromium Cr(VI) as a carcinogen in drinking water is widely reported. Cr can accumulate in corrosion scales in drinking water distribution systems (DWDSs) and act as the potential source for Cr(VI) release. The goal of this dissertation is to elucidate the mechanisms of Cr(VI) formation through the oxidation of Cr solids by disinfectant free chlorine, and to provide control strategies for Cr(VI) formation in DWDSs. First, X-Ray Absorption Spectroscopy (XAS) analysis discovered that zerovalent Cr(0) coexisted with trivalent Cr(III) in the corrosion scales. The oxidation of the corrosion scales by residual disinfectant chlorine released Cr(VI) and exhibited a three-phase kinetics behavior: an initial 2-hour fast reaction phase, a subsequent 2-to-12-hour transitional phase and a final 7-day slow reaction phase approximately two orders of magnitude slower than the initial phase. Because Cr(0)(s) exhibited a much higher reactivity than Cr(III)(s), the oxidation of Cr(0)(s) in the iron corrosion scales was the dominant reaction for the Cr(VI) formation in drinking water. Second, the corrosion control strategies through adjustments of chemical water parameters were investigated. The results showed an increase in pH, silicate, alkalinity, and calcium suppressed Cr(VI) formation that was mainly attributed to in situ surface precipitation of new Cr(III) solids on the surface of Cr(0)(s), including Cr(OH)3(s), Cr2(SiO3)3(s), CrPO4(s), Cr2(CO3)3(s) and Cr10Ca(CO3)16(s). The Cr(III) surface precipitates were much less reactive with chlorine than Cr(0)(s) and suppressed the Cr redox reactivity. Adding phosphate either promoted or inhibited the Cr(VI) formation, depending on the concentration. Third, it is investigated that the effects of bromide and manganese on Cr(VI) formation through the oxidation of Cr(0)(s) by free chlorine. The present of Br- and Mn2+ significantly enhanced the Cr (VI) formation. Br- and Mn2+ can react with free chlorine to form free bromine and manganese dioxide. Free bromine had faster reaction kinetics with Cr(0)(s) than free chlorine. Although manganese dioxide had slower reaction kinetics with Cr(0)(s) than free chlorine, it can accelerate the reaction between Cr(0)(s) and free chlorine. The outcome of this study aimed to provide control strategies to minimize Cr(VI) formation by inhibiting Cr(0) reactivity in drinking water distribution systems.

Multilevel multiphase voltage source inverters have been increasingly attractive to the industry and academia with the development of multiphase machine drive systems. Although the additional phase legs and fast switching semiconductors complicate the control strategies, the advantages of multiphase multilevel inverters are considerable: the voltage and current rating on the semiconductors are reduced, fault tolerance is realized without extra hardware and harmonic spectrum is improved compared with two-level voltage source inverters. This thesis focuses on the development and practical assessment of a five-phase three-level pulse-width modulated (PWM) voltage source inverter (VSI) and associated modulation techniques. The PWM VSI employs a coupled inductor in each phase-leg to provide three-level output voltages. Compared with the popular three-level neutral-point-clamped inverter, the coupled inductor inverter (CII) uses fewer switching devices, has no dead-time and associated distortion, and does not require dc-link capacitor voltage balancing. The five-phase system increases the possible magnetic configurations. The thesis explores various combinations of magnetic cores—toroidal cores and three-limb cores. The design of the coupled inductors is illustrated, and the core loss is computed. Conventional modulation techniques, both carrier-based PWM techniques and space vector modulation techniques, cannot be directly applied to the CII as they do not achieve volt-second balance of coupled inductor windings. Thus, a new space vector modulation technique is proposed for the five-phase CII, aimed at eliminating the d2q2 sub-plane voltage. Two carrier-based PWM techniques aimed at reducing the common-mode voltage are proposed for multiphase inverters in general and then modified for use in the CII system in order to achieve volt-second balance in the coupled inductors. Mathematical models of the coupled inductors, total inverter current and current stress on the dc-link capacitors are established, based on sinusoidal PWM and the two proposed carrier-based PWM techniques for the CII. This provides an insight into the influence of the coupled inductors on the system, in terms of system efficiency and current stress in the dc-link capacitors. The five-phase CII is compared with the five-phase neutral-point-clamped inverter with the implementation of several carrier-based PWM techniques, namely sinusoidal PWM, the proposed common-mode voltage reduction techniques, and harmonic injection PWM, in terms of the efficiency, total harmonic distortion and the load current ripple. A five-phase CII test rig is developed, controlled by a combination of DSP and FPGA. The effectiveness of the proposed modulation strategies is verified by experiment on a passive RL load but also on a five phase motor load with closed-loop control (vector control and hysteresis control).

In this work the transition metal dichalcogenide WSe₂ is exfoliated and characterized. It is shown from the electrical measurements that the material can display both p-type conduction as well as ambipolar characteristics. WSe₂ flakes were also oxidized through thermal and laser treatments to produce oxide structures. The structures and oxidation processes are characterized and described in this thesis.