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Natural Language Generation (NLG) is the automatic generation of Natural Language (NL) by computer in order to meet communicative goals. One aim of NL processing (NLP) is to allow more natural communication with a computer and, since communication is a two-way process, a NL system should be able to produce as well as interpret NL text. This research concerns the design and implementation of a NLG module for the LOLITA system. LOLITA (Large scale, Object-based, Linguistic Interactor, Translator and Analyser) is a general purpose base NLP system which performs core NLP tasks and upon which prototype NL applications have been built. As part of this encompassing project, this research shares some of its properties and methodological assumptions: the LOLITA generator has been built following Natural Language Engineering principles uses LOLITA's SemNet representation as input and is implemented in the functional programming language Haskell. As in other generation systems the adopted solution utilises a two component architecture. However, in order to avoid problems which occur at the interface between traditional planning and realisation modules (known as the generation gap) the distribution of tasks between the planner and plan-realiser is different: the plan-realiser, in the absence of detailed planning instructions, must perform some tasks (such as the selection and ordering of content) which are more traditionally performed by a planner. This work largely concerns the development of the plan- realiser and its interface with the planner. Another aspect of the solution is the use of Abstract Transformations which act on the SemNet input before realisation leading to an increased ability for creating paraphrases. The research has lead to a practical working solution which has greatly increased the power of the LOLITA system. The research also investigates how NLG systems can be evaluated and the advantages and disadvantages of using a functional language for the generation task.

The Xerox Research Centre of Canada has noted that elastomeric cleaning blades in laser printers have a relatively short life expectancy, as they experience high levels of friction and wear while wiping excess toner from commercial photoconducting drums. As such, there has been interest in examining the behaviour related to friction, wear and lubrication of components in laser printers. Molecular dynamics simulations were employed to gain molecular-level insight into the mechanism of wear of the cleaning blade and the effectiveness of lubricants in reducing friction forces. The Dreiding force field was chosen to simulate representations of the photoconducting drum, cleaning blade and the lubricant. They were modeled in bulk and layered forms, and compressed and sheared to examine slip mechanisms and evaluate shear stresses and friction coefficients. It was found that the polycarbonate (PC) component was significantly stronger than either the polyurethane (PU) or octadecane (C18) components, and that the introduction of an interface and/or C18 lubricating material lowered the measured shear strengths to various degrees. The simulations indicated three different slip mechanisms depending on the nature of system. We have observed that shearing may induce structural changes within the PU component (such as ordering) even without a local slip event, which likely contributes to the eventual mechanical failure of the PU cleaning blade. From the models used in this study, it appears that more lubricating material is required than is currently used in practice in order to prevent wear of the PU cleaning blade. As well, the shear strengths and friction coefficients are not significantly reduced with the addition of lubricant for models containing PU. This is, of course, subject to the limitations of the simulations performed. / Thesis (Master, Chemistry) -- Queen's University, 2013-11-05 11:50:34.293

This thesis will consider the following assumptions which are based on a few insights about the artic climate: (1)the artic climate can be characterised by a growing season called summer and a dormat season called winter (2)in the summer season growing conditions are reasonably favourable and species are more likely to compete for plentiful resources (3)in the winter season there would be no further growth and the plant populations would instead by subjected to fierce weather events such as storms which is more likely to lead to the destruction of some or all of the biomass. Under these assumptions, is it possible to find those change in the environment that might cause mutualism (see section 1.9.2) from competition (see section 1.9.1) to change? The primary aim of this thesis to to provide a prototype simulation of growth of two plant species in the artic that: (1)take account of different models for summer and winter seasons (2)permits the effects of changing climate to be seen on each type of plant species interaction.

The cerebral cortex of mammals comprises a series of topographic maps, forming sensory and motor areas such as those in the visual, auditory, and somatosensory systems. Understanding the rules that govern the development of these maps and how this topographic organization relates to information processing is critical for the understanding of cortical processing and whole brain function. Previous computational models have shown that topographic maps can develop through a process of self-organization, if spatially localized patches of cortical neurons are activated by particular stimuli. This thesis presents a series of computational models, based on this principle of self-organization, that focus on the development of the map of orientation preference in primary visual cortex (V1). This map is the prototypical example of topographic map development in the brain, and is the most widely studied, however the same self-organizing principles can also apply to maps of many other visual features and maps in many other sensory areas. Experimental evidence indicates that orientation preference maps in V1 develop in a stable way, with the initial layout determined before eye opening. This constraint is at odds with previous self-organizing models, which have used biologically unfounded ad-hoc methods to obtain robust and reliable development. Such mechanisms inherently lead to instability, by causing massive reorganization over time. The first model presented in this thesis (ALISSOM) shows how ad-hoc methods can be replaced with biologically realistic homeostatic mechanisms that lead to development that is both robust and stable. This model shows for the first time how orientation maps can remain stable despite the massive circuit reconstruction and change in visual inputs occurring during development. This model also highlights the requirements for homeostasis in the developing visual circuit. A second model shows how this development can occur using circuitry that is consistent with the known wiring in V1, unlike previous models. This new model, LESI, contains Long-range Excitatory and Short-range Inhibitory connections between model neurons. Instead of direct long-range inhibition, it uses di-synaptic inhibition to ensure that when visual stimuli are at high contrast, long-range excitatory connections have an overall inhibitory influence. The results match previous models in the special case of the high-contrast inputs that drive development most strongly, but show how the behavior relates to the underlying circuitry, and also make it possible to explore effects at a wide range of contrasts. The final part of this thesis explores the differences between rodents and higher mammals that lead to the lack of topographic organization in rodent species. A lack of organization for orientation also implies local disorder in retinotopy, and analysis of retinotopy data from two-photon calcium imaging in mouse (provided by Tom Mrsic- Flogel, University College London) confirms this hypothesis. A self-organizing model is used to investigate how this disorder can arise via variation in either feed-forward connections to V1 or lateral connections within V1, and how the effects of disorder may vary between species. These results suggest that species with and without topographic maps implement similar visual algorithms differing only in the values of some key parameters, rather than having fundamental differences in architecture. Together, these results help us understand how and why neurons develop preferences for visual features such as orientation, and how maps of these neurons are formed. The resulting models represent a synthesis of a large body of experimental evidence about V1 anatomy and function, and offer a platform for developing a more complete explanation of cortical function in future work.

Managing Surface Ambiguity in the Generation of Referring Expressions (Imtiaz Hussain Khan) Most algorithms for the Generation of Referring Expressions tend to generate distinguishing descriptions at the semantic level, disregarding the ways in which surface issues can affect their quality. This thesis explores the role of surface ambiguities in referring expressions and how the risk of such ambiguities should be taken into account by an algorithm that generates referring expressions. This was done by focussing on the type of surface ambiguity which arises when adjectives occur in coordinated structures (as in the old men and women). The central idea is to use statistical information about lexical co-occurrence to estimate which interpretation of a phrase is most likely for human readers, and to avoid generating phrases where misunderstandings are likely. We develop specific hypotheses, and test them by running experiments with human participants. We found that the Word Sketches are a reliable source of information to predict the likelihood of a reading. The avoidance of misunderstandings is not the only issue to be dealt with in this thesis. Since the avoidance of misunderstandings might be achieved at the cost of very lengthy (or perhaps very disfluent) expressions, it is important to select an optimal expression (i.e., the expression which is preferred by most readers) from various alternatives available. Again, we develop specific hypotheses, and recorded human preferences in a forced-choice manner. We found that participants preferred clear (i.e., not likely to be misunderstood) expressions to unclear ones, but if several of the expressions were clear then brief expressions were preferred over their longer counterparts. The results of these empirical studies motivated the design of a GRE algorithm. The implemented algorithm builds a plural distinguishing description for the intended referents (if one exists), using words; applies transformation rules to the distinguishing description to construct a set of distinguishing descriptions that are logically equivalent. Each description in the set is realised as a corresponding English noun phrase (NP) using appropriate realisation rules; the most likely reading of each NP is determined. One NP is selected for output. A further experiment verifies that the kinds of expressions produced by the algorithm are optimal for readers: they are understood accurately and quickly by readers.

Choke valves are important components in oil and gas production systems that are used to control the pressure and flowrate of fluids issuing from oil and gas reservoirs. The presence of sand in the production fluids can cause considerable damage to such components, and as sand is increasingly becoming an issue in oil and gas production, valve manufacturers need to find ways of reducing their product's susceptibility to solid particle erosion. A CFD-based erosion modelling tool is achieved by first solving the fluid flow through the component of interest; tracking particles through the fluid and extracting impact data on all solid surfaces; and finally relating the particle impact data to erosive wear through a semi-empirical equation. The present study has focussed on the development and validation of a CFD-based erosion modelling method for simple and complex geometries. Erosion testing has been carried out on a range of choke valve materials to provide the fundamental data required in constructing equations that relate erosion rate to particle impact velocity and angle. These equations have in turn been implemented in a commercial CFD code to provide the complete erosion modelling solution. Validation of the method has been effected by comparing predicted results to experimental test data for both simple and complex geometries. Both single phase and abrasive flows have been considered in comparisons. For the simple geometries, reasonable agreement was obtained between predicted and measured pressure drop for the simplest cases, but predicted mass loss was considerably less than the measured amount. With the complex geometries (Multi-Orifice Sleeve choke valves), good agreement for pressure drop was obtained for some valve positions, but not so good for others. Significant differences were observed in mass loss predictions for the complex geometries, which raise questions as to the usefulness of CFD-based methods for predicting component lifetime.