Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: John Kappelman. Vita. Includes bibliographical references.

Thesis (Ph. D.)--Ohio State University, 2007. / Title from first page of PDF file. Includes bibliographical references (p. 81-87).

The influence of the human facial image was surveyed and the nature of its many interpretations were examined. The role of distinctiveness was considered particularly relevant as it accounted for many of the impressions of character and identity ascribed to individuals. The notion of structural differences with respect to some selective essence of normality is especially important as it allows a wide range of complex facial types to be considered and understood in an objective manner. A software tool was developed which permitted the manipulation of facial images. Quantitative distortions of digital images were examined using perceptual and recognition memory paradigms. Seven experiments investigated the role of distinctiveness in memory for faces using synthesised caricatures. The results showed that caricatures, both photographic and line-drawing, improved recognition speed and accuracy, indicating that both veridical and distinctiveness information are coded for familiar faces in long-term memory. The impact of feature metrics on perceptual estimates of facial age was examined using 'age-caricatured' images and were found to be in relative accordance with the 'intended' computed age. Further modifying the semantics permitted the differences between individual faces to be visualised in terms of facial structure and skin texture patterns. Transformations of identity between two, or more, faces established the necessary matrices which can offer an understanding of facial expression in a categorical manner and the inherent interactions. A procedural extension allowed generation of composite images in which all features are perfectly aligned. Prototypical facial types specified in this manner enabled high-level manipulations to be made of gender and attractiveness; two experiments corroborated previously speculative material and thus gave credence to the prototype model. In summary, psychological assessment of computer-manipulated facial images demonstrated the validity of the objective techniques and highlighted particular parameters which contribute to our perception and recognition of the individual and of underlying facial types.

Over the last two decades, the study of 'repetition effects' in behavioural and Event Related Potential (E.R.P) research has originated and added to theories of memory organisation. In this series of experiments, behavioural and E.R.P correlates of human and monkey visual memory were investigated, using the repetition effect as the main index of processing, and manipulating the semantic content of the experimental stimuli. The research has a large founding in established results from lexical studies. The use of pictorial material in this series of experiments extends these results to more general visual memory functions. E.R.P recordings were taken from two monkeys trained extensively to perform a matching-to-sample picture recognition task. The waveforms generated by novel instances of highly familiar pictures were compared to those elicited by repeats. In a further study with unfamiliar pictures the repetition of items had an effect on the evoked potentials for only one of the two subjects. Two further studies were made with one monkey viewing unfamiliar and familiar face pictures. In both these studies, an early potential emerged which was more positive in response to faces than to objects. In order to investigate the importance of the semantic content of stimulus items for memory processes, human E.R.Ps generated by novel and repeated presentations of 'meaningful' and 'meaningless' pictorial images were recorded. Repetition of the meaningful (but not meaningless) pictures attenuated the N400 component associated with the first presentation of a stimulus.

The aims of this thesis are two-fold. The first is to develop computer graphics that allow quantitative manipulation of complex visual stimuli. The second is to show that such techniques have utility in the domain of perceptual psychology. There are three main sections to this thesis. The first section creates methods for performing transformations of facial appearance along particular perceptual dimensions. This work begins with 2-D image manipulations and then extends the general principles to 3-D. Effectiveness of the techniques is illustrated with plates showing transformation in age, gender and identity. The second section uses Genetic Algorithms to control the appearance of 3-D computer graphics objects and investigates methods of evolving objects that embody various consumer concepts. Computer graphic models of shampoo bottles are successfully evolved to satisfy a selection of aesthetic and perceptual characteristics. The final section returns to facial stimuli and extends the Genetic Algorithm approach to investigate aesthetic preference for 3-D facial surfaces. The study shows that individual human subjects can evolve facial surfaces based upon their own attractiveness preferences. The faces evolved are non-average and there is consistency between subjects about preferred characteristics. The three parts of this thesis have different theoretical backgrounds and literature relevant to each topic is therefore reviewed at the start of each section.

The mechanism of predator categorization has not been understood well yet. I examined how coloration pattern and predator size influence categorization by a prey under laboratory conditions. I tested the reaction of great tit (Parus major) to the plush dummies of sparrowhawk (Accipiter nisus), coloured as sparrowhawk, pigeon, robin and great tit. The same color variations were made in the sizes of a sparrowhawk and great tit. My results indicate that the coloration plays the main role in the recognition. The size is not important in the dummies coloured as the predator and the conspecific but it plays a role in recognition of other tested dummies (coloured as the pigeon and robin).

The purpose of this study was to assess the decay resistance of wood modified with a variety of chemicals and to attempt to further understand the mechanism by which chemical modification protects wood from decay. Corsican pine (Pinus nigra) sapwood was modified with three cyclic anhydrides; succinic anhydride, alkenyl succinic anhydride (a derivative of succinic anhydride with a 16-18 carbon alkenyl chain) and phthalic anhydride, and with two more widely studied modifying chemicals; acetic anhydride and butyl isocyanate. All reactions were carried out using pyridine as solvent and catalyst. Modified wood was tested against decay fungi in a pure culture test against basidiomycete fungi (Coniophora puteana, Gloeophyllum trabeum, Trametes versicolor and Pycnoporus sanguineus) under different moisture content regimes, an unsterile soil soft rot test, a fungal cellar test and a field trial. Butyl isocyanate proved the most effective modifying chemical at protecting wood from decay, followed by acetic anhydride and then alkenyl succinic anhydride. Uneven distribution of the modifying chemical in wood was evident using each of these three chemicals, particularly in the case of acetic anhydride. Despite its apparent ability to control decay by basidiomycete fungi, alkenyl succinic anhydride was unable to completely protect wood from soft rot fungi. Phthalic and succinic anhydride modifications both proved susceptible to hydrolysis and leaching, and neither were effective as wood protection chemicals. Phthalic anhydride modified wood performed well in the pure culture test, apparently through biocidal action, but was susceptible to decay in unsterile conditions. The approach made in this study to understanding the mechanism of protection was to analyse physical properties of the modified wood cell wall. This involved the measurement of adsorption isotherms, volumetric swell due to water soak, and cell wall pore size (using the solute exclusion technique). Neither the moisture content of modified wood nor its cell wall moisture content (measured as the fibre saturation point from the adsorption analysis) provided a good explanation of decay resistance. In several cases, the relationship between volumetric swell (due to water soak) and weight loss (to a given fungus in pure culture) was found to be consistent between modification types. From this it is concluded that the extent by which water swells modified wood is important to decay resistance. A reduction in cell wall pore volume was measured using the solute exclusion technique, though no further conclusions could be drawn from this test. It is proposed that the mechanism of resistance to decay by basidiomycete fungi involves the blocking of cell wall pores, which restricts the access of degradative agents released by decay fungi. The amount by which wood swells is important in this theory since this will determine by how much transient pores in modified wood can open, and whether enough space is created to bypass this blocking effect. The possibility of the role of site substitution in decay resistance is not discounted, and may contribute to decay resistance, particularly against white rot fungi. Pore blocking is not thought to be the mechanism of protection against soft rot fungi. In this case the substitution and shielding of decay susceptible sites are thought to be more important.

Biomass from forestry and agricultural sources has recently drawn a lot of attention as a new source of feedstock for energy and bio products. Size reduction is an important step in preparation of biomass as a feedstock. Each conversion process needs its own specific size or size distribution of particles. Modeling the size reduction process helps to optimize the design and control of the process while ensuring biomass particle sizes for an efficient biofuel conversion process. The objective of this study was to apply the population balance method for modeling the size reduction process. The model was applied to switchgrass size reduction by a grinder. Two population balance parameters, grinding rate (s⁻¹) and breakage distribution function (dimensionless) were estimated using experimental grinding data. The time dependent balance equations were solved using the Euler technique. The accumulation and depletion of the particles belonging to each size category were simulated as a function of time. The simulation predicted the residence time of particles inside the grinder in a way that the ground particles could meet the size and size distribution specifications for the downstream process. The thesis also describes preliminary steps in size reduction. Ground particles were fractionated based on their size by sieving. Weibull distribution was found to be the best probability density function to fit the data. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

In the comminution industry, cone crushers are widely used for secondary and subsequent stages of size reduction. For a given crusher, the achieved size reduction is governed by the closed-side setting. Hadfield Steel is commonly used to line the crushing members to minimize wear. Yet, liner wear caused by some rock types can still be excessive. Enlargement of discharge opening induced by wear of liners produces a drift in product size which, if unchecked, can lead to high volumes of re-circulating load. Alteration of closed-side setting is now commonly achieved via hydraulic means. However, compensation of liner wear still involves plant shut down and loss of production.

The effect of particle size distribution (PSD) on the performance of a fluidized bed reactor was investigated using the ozone decomposition reaction, combined with the study of hydrodynamics, for fresh and spent fluid cracking catalysts, each having three particle size distributions - wide, narrow and bimodal - all with nearly the same mean diameter (60 µm), the same particle density and the same BET surface area. The superficial gas velocity was varied from 0.1 to 1.8 m/s to include the bubbling, slugging, turbulent and fast fluidization regimes. The catalytic rate constant, based on the volume of the particles, ranged from 2 to10 s⁻¹, while the static bed height was varied from 0.15 m to 1 m. Four different multi-orifice gas distributors with different hole diameters (2.2 to 5.1 mm) and hole numbers (4 and 21) were also tested to evaluate the influence of gas distributor on the performance of fluidized bed reactors. The particle size distribution was found to play a larger role at higher gas velocities than at lower velocities. At low gas velocities (Uf ≤ 0.2 m/s), the reaction conversion was not greatly affected by the PSD. However, with an increase in gas velocity the PSD effect became larger. The wide size distribution gave the highest reactor efficiency, defined as the ratio of the volume of catalyst required in a plug flow reactor to that required in the fluidized bed reactor to achieve the same conversion, while the narrow blend gave the lowest. The differences are not solely a function of the "fines content". The influence of particle size distribution on the hydrodynamics of fluidization was evaluated by measuring particle concentrations in voids, bubble sizes, and dense phase expansion. When the superficial gas velocity exceeded 0.1 m/s, the bed with the wide size distribution usually gave the highest particle concentration inside the voids, the smallest bubble size and the greatest dense phase expansion at the same operating conditions. There is evidence that there is a greater proportion of "fines" present in the voids than in the overall particle size distribution. This has been explained in terms of the throughflow velocity inside bubbles being of the same order as the terminal velocity of typical "fines", causing these particles to spend longer periods of time inside the voids. The effect of the PSD on the fluidization regime and its transitions was determined by measuring pressure fluctuations along the column. The earliest transition from bubbling or slugging to turbulent fluidization occurred in the bed of wide size distribution, while the latest corresponded to the narrow PSD. For particles of wide size distribution, higher conversion was achieved for the turbulent and fast fluidization regimes than for the bubbling fluidization regime under otherwise identical conditions, while for particles of narrow size distribution, the dependence of conversion on regime was small. Hence, for reactors of wide PSD, the performance can be improved significantly by operating in the turbulent or fast fluidization regime, while for particles of narrow size distribution, the benefit of operating at high gas velocity is slight at best. The PSD influence should be considered in modelling fluidized bed reactors. The "Two-Phase Bubbling Bed Model" has been modified to account for PSD effects. For the reactor of wide particle size distribution operated at high gas velocities, a single-phase axial dispersion model with closed inlet and open outlet boundary conditions appears to be suitable to predict the performance. It was also found that a high pressure drop across the gas distributor was not sufficient to maintain good performance of the distributor. The reactor efficiency in the entry region was higher for a distributor with a greater number of orifices, even though it had a lower pressure drop, than for a distributor plate with fewer larger holes. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate