Autonomous deterministic epidemiological models are known to be asymptotically stable. Asymptotic stability of these models contradicts observations. In this thesis we consider some factors which were suggested as able to destabilise the system. We consider discrete-time and continuous-time autonomous epidemiological models. We try to keep our models as simple as possible and investigate the impact of different factors on the system behaviour. Global methods of dynamical systems theory, especially the theory of bifurcations and the direct Lyapunov method are the main tools of our analysis. Lyapunov functions for a range of classical epidemiological models are introduced. The direct Lyapunov method allows us to establish their boundedness and asymptotic stability. It also helps investigate the impact of such factors as susceptibles' mortality, horizontal and vertical transmission and immunity failure on the global behaviour of the system. The Lyapunov functions appear to be useful for more complicated epidemiological models as well. The impact of mass vaccination on the system is also considered. The discrete-time model introduced here enables us to solve a practical problem-to estimate the rate of immunity failure for pertussis in New Zealand. It has been suggested by a number of authors that a non-linear dependence of disease transmission on the numbers of infectives and susceptibles can reverse the stability of the system. However it is shown in this thesis that under biologically plausible constraints the non-linear transmission is unable to destabilise the system. The main constraint is a condition that disease transmission must be a concave function with respect to the number of infectives. This result is valid for both the discrete-time and the continuous-time models. We also consider the impact of mortality associated with a disease. This factor has never before been considered systematically. We indicate mechanisms through which the disease-induced mortality can affect the system and show that the disease-induced mortality is a destabilising factor and is able to reverse the system stability. However the critical level of mortality which is necessary to reverse the system stability exceeds the mortality expectation for the majority of human infections. Nevertheless the disease-induced mortality is an important factor for understanding animal diseases. It appears that in the case of autonomous systems there is no single factor able to cause the recurrent outbreaks of epidemics of such magnitudes as have been observed. It is most likely that in reality they are caused by a combination of factors. / Subscription resource available via Digital Dissertations

This thesis aimed to understand the relationship between the Apple brand and Apple consumers. It presents an historical semiotic analysis of a selection of the Apple brand from 1978 to 2009 and in-depth interviews with Apple consumers. The interviews were then analysed thematically, looking at the ways participants employed Apple in the construction of identity. The thesis extends theoretical critical approaches to branding with the inclusion of participant interviews. Approaches to branding consider the role of consumers in brand production and ownership, but this thesis moves focus beyond abstraction to interrogate how much of consumer participation is predetermined by the brand. This was achieved by actually examining the ways in which brand consumers articulate the brand. In doing so findings showed that Apple consumers distinguish themselves from non-Apple consumers, but significantly they made a second distinction. For the first distinction, Apple consumers articulated emotional investment, superior aesthetic taste, and feelings of being part of an exclusive community. The second distinction is an articulation of uniqueness within the Apple community. This is achieved through creating a sense of critical distance from consumption via individual lifestyle and taste.

This thesis explores and develops the potential of interactive television (iTV) technology for language learning. Through a modified form of the socio-cognitive engineering approach (Sharpies et al., 2002a), a range of learner centred design activities were carried out and a system developed to provide cross platform support, blending iTV and mobile phones, for adult language learners.

The research reported in this thesis investigates preschoolers‟ interactions with interactive television applications. The study involved the development of an electronic programme guide prototype and the empirical evaluation thereof. There were three main aims. The first aim was to analyse children‟s interactions and illustrate them in a framework to further understanding of the way preschoolers interact with the television. The second aim was to contribute design principles for preschool interactive television and the third aim was to refine methods and add to the knowledge of design and evaluation techniques involving young children.

The research reported in this thesis explores issues of information design for mobile devices, in particular those relating to selection and presentation of on-screen information and interactive functionality for users of mobile phones. The example domain is that of mobile tour guides for tourists, local people, students and families. Central to the research is the issue of multimodality, particularly the graphic and interaction design issues involved in viewing video, in combination with other media, on a mobile device, in an outdoor context. The study produced three main results: 1. An analytical framework for user-experience concerns in cultural heritage settings, 2. Design recommendations for outdoor mobile multimedia guides and 4. Refinements in methods for collecting and analysing data from fieldwork with visitors in cultural heritage settings. Those results were formulated for the use of mobile guide designers. The methodology used to inform and structure the work was Design Research, involving literature review and empirical work, including user trials of a prototype tourist guide developed in the project. The literature review covered areas of tourism, multimedia design, mobile HCI and existing mobile guides. Outdoor fieldwork exercises were carried out with three different cultural information sources - human tour guide, paper based guide and mobile guide app - in order to identify any problems that visitors might have and to gather requirements for the development of a mobile cultural guide. Qualitative analysis was applied to analyse the video observations and questionnaires completed during the tours. Requirements were grouped and analysed to give substantial information for a conceptual design. Personas and scenarios were created based on real participants and situations that occurred on the tours. A mobile guide prototype was developed and evaluated in the field with visitors. Qualitative analysis and descriptive statistics were used to analyse the data. Visitors were asked about their preferences among various multimedia design elements and answered a questionnaire on their experience. The elements that affect the user experience with outdoor mobile guides were categorised and organised into a framework. It became apparent that users' experience of technology (in this case the mobile tourist guide) and environment are affected by context, content and look and feel elements. This framework of user experience generated a design toolkit with a collection of recommendations for designers of such systems. The recommendations are described in context of usage and have a rating system with strength of evidence and confidence based on how often they appeared in the field works and solutions tested.

Spider diagrams are a recently developed visual logic that make statements about relationships between sets, their members and their cardinalities. By contrast, the study of regular languages is one of the oldest active branches of computer science research. The work in this thesis examines the previously unstudied relationship between spider diagrams and regular languages. In this thesis, the existing spider diagram logic and the underlying semantic theory is extended to allow direct comparison of spider diagrams and star-free regular languages. Thus it is established that each spider diagram defines a commutative star-free regular language. Moreover, we establish that every com- mutative star-free regular language is definable by a spider diagram. From the study of relationships between spider diagrams and commutative star-free regular languages, an extension of spider diagrams is provided. This logic, called spider diagrams of order, increases the expressiveness of spider di- agrams such that the language of every spider diagram of order is star-free and regular, but not-necessarily commutative. Further results concerning the expres- sive power of spider diagrams of order are gained through the use of a normal form for the diagrams. Sound reasoning rules which take a spider diagram of order and produce a semantically equivalent diagram in the normal form are pro- vided. A proof that spider diagrams of order define precisely the star-free regular languages is subsequently presented. Further insight into the structure and use of spider diagrams of order is demonstrated by restricting the syntax of the logic. Specifically, we remove spiders from spider diagrams of order. We compare the expressiveness of this restricted fragment of spider diagrams of order with the unrestricted logic.

A spark ignition (SI) engine operating with a lean burn has the potential for higher thermal efficiency, and lower nitrogen oxide emissions than that of stoichiometric operation. However, a lean or highly diluted mixture leads to poor combustion stability impacting detrimentally upon engine performance. An experimental investigation was carried out, on a 4-valve single cylinder gasoline engine with a split intake tract and two identical production port-fuel injectors installed, allowing independent fuel delivery to each intake valve. The main objective of the study was to extend the limit of lean combustion through the introduction of charge stratification. Novel port fuel injection strategies such as, dual split injection, multiple injections and phased injection, were developed to achieve this goal. In parallel, a model of the engine was developed in the Ricardo WAVE software. The model was used to calculate parameters such as in-cylinder residual gas, for different test points. Combustion stability was improved for the engine conditions tested. At 1000 rpm and 1.0 bar gross indicated mean effective pressure (GIMEP), the lean combustion limit was extended from a 14:1 air-to-fuel ratio (AFR) to 17.5:1. At 1500 rpm and 1.5 bar GIMEP the lean combustion limit was extended from 17.5:1 to approximately 21:1 AFR. Finally for 1800 rpm and 1.8 bar GIMEP, lean combustion was improved from 21: 1 AFR to 22: 1 An experimental spark plug, with an infrared detector, was used to measure the variation in fuel distribution at the spark plug gap. It showed that the different fuel injection strategies generated different levels of fuel concentration. It was identified that injections in a single port created fuel stratification in the spark plug area but were more prone to cycle to cycle variations in fuel concentration. These variations did not correlate with combustion stability or flame speed propagation at the speeds and loads tested. The most important parameter to influence the flame propagation speed was found to be the variation in local lambda with crank angle just after the ignition timing. It was shown that the fastest flame propagation speeds did not necessarily result in the lowest CoV in GIMEP. Finally the fuel injection strategies were investigated for highly dilute conditions, achieved by means of internal residual gas trapping, with the aim of promoting (spark-assisted) compression ignition combustion conditions.

This thesis analyses the structure of natural language queries to document repositories, with the aim of finding better methods for information retrieval. The exponential increase of information on the Web and in other large document repositories during recent decades motivates research on facilitating the process of finding relevant information to meet end users' information needs. A shared problem among several related research areas, such as information retrieval, text summarisation and question answering, is to derive concise textual expressions to describe what a document is about, to function as the bridge between queries and the document content. In current approaches, such textual expressions are typically generated by shallow features, for example, by simply selecting a few most-frequently- occurring key words. However, such approaches are inadequate to generate expressions that truly resemble user queries. The study of what a document is about is closely related to the widely discussed notion of topic, which is defined in many different ways in theoretical linguistics as well as in practical natural language processing research. We compare these different definitions and analyse how they differ from user queries. The main function of a query is that it defines which facts are relevant in some underlying knowledge base. We show that, to serve this purpose, queries are typically formulated by first (a) specifying a focused entity and then (b) defining a perspective from which the entity is approached. For example, in the query 'history of Britain', 'Britain' is the focused entity and 'history' is the perspective. Existing theories of topic often focus on (a) and leave out (b). We develop a theory of extended topic to formalise this distinction. We demonstrate the distinction in experiments with real life topic expressions, such as WH-questions and phrases describing plans of academic papers. The theory of extended topic could be applied to help various application areas, including knowledge organisation and generating titles, etc. We focus on applying the theory to the problem of information retrieval from a document repository. Currently typical information retrieval systems retrieve relevant documents to a query by counting numbers of key word matches between a document and the query. This approach is better suited to retrieving the focused entities than the perspectives. We aim to improve the performance of information retrieval by providing better support for perspectives. To do so, we further subdivide the perspectives into different types and present different approaches to addressing each type. We illustrate our approaches with three example perspectives: 'cause', 'procedure' and 'biography'. Experiments on retrieving causal, procedural and biographical questions achieve better results than the traditional key-word-matching-based approach.

The region of the nuclear chart around A~100 is an area of structural changes where different shapes coexist and therefore, an interesting place to study structural evolution and test nuclear models. Within the clement that populate this region, zirconium is one which is expected to present well deformed states, but for which little experimental data has been measured so far. The structure of the 102-108Zr nuclei has been studied using the Interactiug Boson Model (IBM). Energy states and transition probabilities have been predicted and tested using the limited amount of existing experimental data. However, the results of these calculations produced several possibilities, so knowledge about non-yrast. states is needed in order to deepen the understanding of the structural changes in zirconium nuclei. Therefore a. series of experiments to measure non-yrast states of 102- 108Zr are required. A new technique, for separating different states of nuclei, has been developed and tested at the University of Jyvaskyla, using the IGISOL III facility for the known case of 100Nb β-decay into 100 Mo. This technique has been successfully extended to allow the separate study of the gamma.-ray decay of states populated by the different parent states. Lower spin states of 102- 108Zr are populated via beta-decay from 102- 108y' In order to measure the non-yrast states of 102- 108Zr post-trap online spectroscopy will be used at IGISOL IV. IGISOL IV is the improved version of IGISOL 111 and is currently under construction. Part of my Ph.D. consisted of helping with the development of IGISOL IV, the improvements of this facility are explained in this thesis alongside its operation and several tests performed during 2012.

The certification process of safety critical products for European and other international standards typically demand environmental stress, endurance and electro magnetic compatibility testing. Theoretical, or `static testing' also a requirement. Failure Mode Effects Analysis (FMEA) is a tool used for static testing. FMEA is a bottom-up technique that aims to assess the effects of all component failure modes in a system. Its use is traditionally limited to hardware systems. With the growing complexity of modern electronics traditional FMEA is suffering from state explosion and re-use of analysis problems. Also with the now ubiquitous use of microcontrollers in smart instruments and control systems, software is increasingly being seen as a `missing factor' for FMEA This thesis presents a new modular variant of FMEA, Failure Mode Modular Decomposition (FMMD). FMMD has been designed to integrate mechanical/electronic and software failure models, by treating them all as components in terms of their failure modes. For instance, software functions, electronic and mechanical components can all be assigned sets of failure modes. FMMD builds failure mode models from the bottom-up by incrementally analysing functional groupings of components, using the results of analysis to create higher level derived components, which in turn can be used to build functional groupings. In this way a hierarchical failure mode model is built. Software functions are treated as components by FMMD and can thus be incorporated seamlessly into the failure mode hierarchical model. A selection of examples, electronic circuits and hardware/software hybrids are analysed using this new methodology. The results of these analyses are then discussed from the perspective of safety critical application. Performance in terms of test efficiency is greatly improved by FMMD and the examples analysed and theoretical models are used to demonstrate this. This thesis presents a methodology that mitigates the state explosion problems of FMEA; provides integrated hardware and software failure mode models; facilitates multiple failure mode analysis; encourages re-use of analysis work and can be used to produce traditional format FMEA reports.