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Each day, we are confronted with a large amount of more or less important information that we have to consider, and even in our digital society we need paper for communication, documentation and education. Much of the paper we use or are confronted by in our daily life, such as newspapers, books and packages, contains printed images or texts, and the appearance of both the print and the supporting surface is important. A good contrast between a printed text and the paper makes it easier to read, a detailed print of an illustration makes it more informative, and clear and evenly distributed colours on a package or on a poster make it more appealing. All of these qualities depend on the optical properties of the paper product and the the behavior of light illuminating the different materials. The aim of the work described in this thesis is to characterize the structure of coatings and prints, and to validate models for the optical response and interaction of ink and coating based on optical measurements of physical samples. It is the interactions between the printing ink and the porous structure of the coating layers that are subject to investigation. Experiments have been employed to relate the physical conditions in a flexographic printing nip to the ink setting, affected by the physical and chemical properties of the coating, to the resulting optical response of the printed paperboard. / The aim of the work described in this thesis is to characterize the structure of coatings and prints, and to validate models for the optical response and interaction of ink and coating based on optical measurements of physical samples. It is the interactions between the printing ink and the porous structure of the coating layers that are subject to investigation. Experiments have been employed to relate the physical conditions in a flexographic printing nip to the ink setting and the resulting optical response. By comparing simulated and measured results, it was shown that modifications of the surface properties account for the brightness decrease when substrates are calendered. Light scattering simulations, taking into account the surface micro-roughness and the increase in the effective refractive index, showed that surface modifications accounted for most of the observed brightness decrease, whereas the bulk light scattering and light absorption coefficients were not affected by calendering. Ink penetration affects the print density, mottling and dot gain. Results show that ink distribution is strongly affected by surface roughness, differences in pore size and pore size distribution. For samples having different latex amounts and different latex particle sizes, a higher print force did not increase the depth of penetrated ink to any great extent, but rather allowed the wetting to act more efficiently with a more evenly distributed ink film, a higher print density and fewer uncovered areas as a result. Uncovered areas could be linked both to local roughness variations and to local wettability variations on the surface. Samples with different ratios of calcium carbonate/kaolin clay pigment showed an increased porosity and an increase in print density with increasing amount of kaolin in the coating layer.

The physical state of the seedbed is of importance to the plant environment as it influences some important processes in the soil such as seedling emergence, water and solute transport, and ease of root penetration. This is affected to a large extent by tillage process, the tillage implement type and the geometry of the implement used. / A field experiment was carried out on a clay soil to determine the effect of the geometry of bladed tillage implements on some soil physical properties after tillage. The soil properties evaluated were bulk density, mean clod size distribution and total pore space after tillage and the extent of loosening achieved. / Implement parameters considered were blade width, rake angle and depth of operation of the implement. Two blade widths of 75 and 150 mm were evaluated in combination with three rake angles of 30, 60 and 90 degrees. Each tillage implement was drawn through the soil at four operating depths of 100, 150, 200 and 250 mm. / Larger rake angles were observed to result in larger mean aggregate sizes and greater bulk density reductions when compared to smaller rake angles. Greater reduction in bulk density was observed with the wider of the two blade widths evaluated. Mean clod size after tillage was also observed to be large for the wider of the two widths evaluated. Irrespective of width and rake angle, greater operating depths resulted in larger mean clod sizes and greater reductions in bulk density as compared to shallower operating depths. Fractal analysis showed the extent of fragmentation to be greater at shallower operating depths, hence the small mean clod sizes obtained.

The exploration for unconventional energy reserves has rapidly increased over the last five to ten years. Currently, there are a number of companies actively exploring for coalbed methane (CBM) in New Zealand. This study investigates one of these prospects, the subbituminous Huntly coalfield. Coal core was retrieved from the two major seams in the coalfield, the Renown and the Kupakupa. Three coals types were identified (1) bright lustre, non-banded, (2) bright lustre, moderately banded and (3) bright lustre, highly banded. As the degree of banding increases, the average thickness of the vitrain bands increase, the amount of structured vitrinite macerals also increase and the vitrodetrinite content decreases. The Renown seam is predominantly composed of bright non-banded coal while in the Kupakupa seam the more banded coal types are dominant. On average, the Renown seam has both the capacity to hold more gas and has higher gas contents than the stratigraphically lower Kupakupa seam. Additionally, gas content, on average, was found to be highest in intervals of the non-banded coal type and lowest in the highly banded coal type. Cluster analysis found that gas content is associated with hydrogen, volatile matter, calorific value and collodetrinite. As such, gas appears to be preferentially retained/produced in the matrix-dominated material. While not causally linked with gas content, gas holding capacity showed associations with the sporinite, inertodetrinite, funginite and vitrodetrinite; of note, these macerals are highest in the non-banded coal type. Gas holding capacity is thought to be a function of coal texture. Ash yield was found to inversely affect total gas content when ash yield is >10%. Below 10%, it is thought that inorganic elements are organically bound. The small angle scattering analysis indicated that inorganic matter was in the 12.5 Å < r < 125 Å pore size range. The influence of inorganic material was more noticeable in vitrain than matrix samples and is proposed to exist as thin inorganic coatings. Total porosity of the Huntly coal is primarily composed of micropores with macroporosity only contributing a small proportion. In addition, the specific surface area of the coals is also largely contributed by the micropores. Methane holding capacity on a dry, ash-free basis showed positive correlations with both micro- and macroporosity. When methane holding capacity was considered on an ‘as analysed’ basis, correlation was only identified with macroporosity. Possibly gas holding capacity is affected by the presence of moisture blocking access to gas adsorption sites in smaller pores. Considerable variation is present in both gas adsorption and gas desorption results between drill holes, between seams and also within individual seam intersections. Gas adsorption capacity and gas content are used to calculate % saturation for a reservoir, a key assessment parameter. It was found that multiple samples of both gas adsorption capacity and gas content are required to reduce the uncertainty around the calculated % saturation (at least three of each in the current study). Additionally, adsorption isotherm samples need to be collected as fresh as possible to minimize oxidation and moisture loss. Delaying sample analysis was found to result in an overestimation of gas adsorption capacity.

An understanding of the clogging of fine sediments within gravel substrates is advanced through the use of dimensional analysis and macro-analysis of clogging experiments in hydraulic flumes. Dimensional analysis is used to suggest that the dimensionless clogging depth can be collapsed using the original and adjusted bed-to-grain ratios, substrate porosity, roughness Reynolds number, and Peclet number. Macro-analysis followed by statistical analysis of 146 experimental test results of fine sediment deposition in gravel substrates suggests that the dimensionless clogging depth can be collapsed using the substrate porosity and roughness Reynolds number reflecting the processes of gravity settling and turbulence induced fluid pumping between substrate particles. In addition, a clear cutoff of fine sediment unimpeded static percolation and sediment clogging is found using the adjusted bed-to-grain ratio. Thereafter, a physics-based approach is used to predict the clogging depth of fine sediment in gravel and in turn approve upon the preliminary findings in the empirical analysis. A momentum-impulse model that accounts for the critical impulse of a particle bridge is balanced with a fluid pulse resulting from turbulent pumping. The momentum-impulse model reduces the number of unknown parameters in the clogging problem and increases the model predictability as quantified using k-fold validation and model comparison with the empirical approach. A nomograph derived from applying the momentum-impulse model is provided herein, which will be useful for stream restoration practitioners interested in estimating embeddedness. Also, prediction of the clogging profile is shown using the clogging depth predicted with the momentum-impulse model.

Self-propagating High-temperature Synthesis (SHS) is the synthesis of solid materials by a reaction wave propagating into the initial reactants, typically two metals, which can alloy exothermically. Typically, experiments are performed with the reactants in powder form, with relatively low density. Recent experiments by Bacciochini et al. revealed much larger flame speeds in densified powders near TMD (theoritical maximum density), obtained by the cold spray process. The present thesis investigates why the flame speed increases dramatically with an increase in density of the powders. The investigation rests on the analytical model formulated by Makino by controlling how the variables are affected by changes in density. Flame speed measurements were performed in mixtures of nickel (Ni) and aluminum (Al) at different initial densities. The density was varied by controlling the cold-pressing of the samples inside metallic channels and tubes. Experiments were also performed in ball-milled powders, in order to permit comparison with the experiments performed by Bacciochini in these mixtures at nearly maximum densities. The measurements revealed that the flame speed increases with the initial density, with a discontinuous transition occurring at approximately 60% theoretical maximum density (TMD). This transition also corresponds to the point where the powders deform plastically during the compaction process, suggesting that the intimate contact between the particles is responsible for the flame speed increase. The flame speed dependence on powder density is attributed to the changes in the heat conductivity of the pressed powders. At high densities, where the powders have plastically deformed, the continuous structure yields conductivities close to the idealized solid matrix. At these high densities, the conductivity was modeled using the Effective Medium Theory (EMT). Analytical predictions of the flame speed, using available thermo-chemical data for the Al-Ni system were found in good agreement with the present experiments at high densities. At low densities, since Al-Ni is a mixture of loose powders, the EMT model is no longer applicable. Thus, the thermal conductivity was experimentally measured and then was fitted using the semi-empirical model suggested by Aivazov. Using this data, Makino's model predicts the correct flame speed dependence observed experimentally. The present thesis has thus established that the dependence of flame speed on density is due mainly to the changes in the structure and thermal conductivity of the powders.

Persistent soil compaction by heavy-axle-load vehicles is a growing concern for the long-term productivity of clay soils. For optimum soil management, however, we must be able to evaluate adequately soil structural damages. This study compares different methods of assessing soil structure as affected by compaction and subsoiling treatments in a clay soil under corn production. / The tests used were: total porosity as calculated from densimeter readings and from soil cores; structural porosity; water desorption characteristics; and soil profile examination. These tests were performed in three layers of 20 cm and evaluation was based on their practicality and their ability to differentiate between treatments and to correlate with corn yield. / The results confirm that total porosity is a poor indicator of compaction in the subsoil. In soil profile assessments, ped descriptions were preferable to examination of pores. Water content and saturation deficit at $-$4.0 and $-$100 kPa were the best indicators of treatments and plant response.

Screens may be utilized efficiently for dissipating the energy of water. In this study, water flowing beneath a gate is used to simulate the flow downstream of a hydraulic structure and screens are used as an alternative mean for energy dissipation. Investigations are done conducting a series of experiments. The porosity, thickness, and the location of the screens are the major parameters together with the Froude number of the upstream flow. The scope of this thesis covers the situation where there is a pseudo-jump formation. The experiments covered a range of Froude numbers between 5 and 18, porosities between 20% and 60%, and location of the screen up to 100 times of the undisturbed upstream flow depth. The thicknesses of the screens used are in the order of the undisturbed upstream flow depth. The results show the importance of each parameter on the energy dissipating performance of the screens and the system. It is observed that screens dissipate more energy than a jump within the range covered in these studies.

This study focuses on the effect of different experimental conditions including conventional hydrothermal synthesis and supercritical carbon dioxide (SCCO2) methods on materials characteristics in terms of particle morphology and pore geometry. Three types of mesoporous silicas were investigated by different synthesis methods, that is, MCM- 41, SBA-15 and -16. These materials were used as a target molecule due to its high volatility and strong antimicrobial characteristics. / Thesis (PhDAppliedScience)--University of South Australia, 2008.

Thesis (Ph.D.)--University of Western Australia, 2007.