Surface spectroscopic techniques have been applied to facets of the flotation beneficiation and hydrometallurgical extraction of sulfide minerals to enhance the fundamental understanding of these industrially important processes. As a precursor to the determination of surface chemical composition, the sub-surface properties of some sulfide minerals that have not previously been fully characterised were also investigated. The electronic properties of ??-NiS and ??-NiS (millerite), Ni3S2 (heazlewoodite), (Ni,Fe)9S8 (pentlandite), CuFe2S3 (cubanite), CuFeS2 (chalcopyrite), Cu5FeS4 (bornite) and CuS (covellite) were investigated by conventional and synchrotron X-ray photoelectron spectroscopy (XPS) and near-edge X-ray absorption fine structure (NEXAFS) spectroscopy augmented by ab initio density of state calculations and NEXAFS spectral simulations. Particular aspects studied included the relationship between sulfur coordination number and core electron binding energies, the higher than expected core electron binding energies for the sulfur in the metal-excess nickel sulfides, and the formal oxidation states of the Cu and Fe in Cu-Fe sulfides. It was concluded that the binding energy dependence on coordination number was less than previously believed, that Ni-Ni bonding was the most likely explanation for the unusual properties of the Ni sulfides, and that there was no convincing evidence for Cu(II) in sulfides as had been claimed. Most of the NEXAFS spectra simulated by the FEFF8 and WIEN2k ab initio codes agreed well with experimental spectra, and the calculated densities of states were useful in rationalising the observed properties. XPS, static secondary ion mass spectrometry (SIMS) and NEXAFS spectroscopy were used to investigate thiol flotation collector adsorption on several sulfides in order to determine the way in which the collector chemisorbs to the mineral surface, to differentiate monolayer from multilayer coverage, and to characterise the multilayer species. It was found that static SIMS alone was able to differentiate monolayer from multilayer coverage, and together with angle-resolved NEXAFS spectroscopy, was also able to confirm that 2-mercaptobenzothiazole interacted through both its N and exocyclic S atoms. The altered layers formed on chalcopyrite and heazlewoodite during acid leaching were examined primarily by means of threshold S KLL Auger electron spectroscopy, but no evidence for buried interfacial species was obtained.

[Abstract]: Infiltration variability is a major issue during the design phase and management for all types of irrigation systems. Infiltration is of particular significance for furrow irrigation and other forms of surface irrigation as the soil intake rate at any given position not only determines the depth applied but also governs the distribution of water to other locations in the field. Despite this, existing measurement and evaluationprocedures generally assume homogeneous soil infiltration rates across the field to simplify data collection and computational requirements. This study was conducted to(a) determine whether spatial and temporal variations in soil infiltration characteristics have a significant impact on the performance of surface irrigation and (b) identify more appropriate management strategies that account for this variability and substantially improve irrigation performance.The soil infiltration rate is typically expressed as an empirical function of opportunity time. The infiltration function parameters cannot be directly measured but are commonly estimated from field hydraulic measurements using an appropriate simulation model. The volume balance model as used in the inverse solution for infiltration (e.g. Two Point Method) was modified to enable runoff data collected during the inflow period to be used in the estimation of the infiltration parameters. The resulting model, IPARM also accommodates the full (variable) inflowhydrograph rather than relying on a constant inflow assumption. Inclusion of runoff data in the inverse solution improved the accuracy of the infiltration curve during the runoff phase and hence offered the greatest benefit where the irrigation time exceededthe completion of advance. Analysis of field data collected from multiple furrows at a single site indicated that accounting for the variable inflow in IPARM both reduced the variability (e.g. reduction in the coefficient of variance (CV) of cumulative infiltrated depths of 18.6% and 11.5% at opportunity times of 100 and 500 minutes,respectively) and standardised the shape of the estimated infiltration curves. Hence, a significant proportion of the apparent variability in soil infiltration rates was shown to be a consequence of the constant inflow assumption. Sensitivity analysis indicatedthat IPARM is highly sensitive to the runoff measurements but is not influenced by the relative numbers of advance and runoff data points. Validation of IPARM estimated infiltration parameters using the full hydrodynamic model SIRMOD showed that the inclusion of runoff data in the inverse procedure did not compromise the ability to predict the measured advance trajectory but significantly improved the fit to the measured runoff volumes (average decrease in absolute error of simulated runoff volumes of 84%). Whereas the use of runoff data enabled SIRMOD to estimate runoff volumes, accounting for variable inflow improved the fit of the predicted runoff rates to the shape of the measured outflow hydrograph.Field data collected from several sites across the Darling Downs, Queensland has shown that the infiltration rates vary significantly (e.g. by up to 65% at 500 minutes),both spatially between furrows and temporally over the season. For the sites studied, the spatial variance in infiltration was surpassed by the seasonal variance (e.g. average CV of infiltration of 33.1% compared to 12.5%) but no consistent trends were identified. It was found that the lognormal distribution provided the best fit for thevariance in the infiltration curves which was in turn strongly related to the statistical distribution of the infiltration term of the volume balance. From this research, a procedure was developed to predict the infiltration parameters using a single advancepoint and any number of “known” infiltration curves from the same field.The IrriProb model was developed to extend the process of simulation from a single furrow scale to the whole field scale. IrriProb performs the full hydrodynamicsimulation for multiple independent furrows which are combined to form a spatial representation of the water application. Each furrow can have a unique infiltrationrate, inflow rate (Q), time to cut off (TCO) and soil moisture deficit. Validation of IrriProb using multiple sets of field data demonstrated that the single furrowsimulations failed to predict the true whole field irrigation performance (e.g. furrow distribution uniformity (DU) between 72.2% and 86.2% compared to the whole field DU of 64.8%).An optimisation routine was developed within IrriProb to maximise irrigation performance through identification of optimal values of Q and TCO. The optimisation objective function is comprised of a Boolean combination of customisable performance criteria. The user selects the appropriate performance terms and the optimal management is determined through a graphical overlay of the complyingranges of Q and TCO. Hence, the objective function of IrriProb retains the importance of each individual performance term, an advantage over those based on numerical combinations of weighted terms. Simulation of the whole field application under practical ranges of Q and TCO demonstrated the complex interactions between theperformance indices (e.g. the trade off between requirement efficiency (RE) and application efficiency (AE)). In cases of low infiltration variability it was possible to optimise the whole field performance using a single value of Q and TCO. However, under increased infiltration variability it was more appropriate to manage the field using two or more different management strategies. Irrigation optimisation based onmeasurements from a single furrow or the average infiltration curve, cannot identify the optimal combination of Q and TCO for the whole field. Simulation of field management based on the optimisation strategy obtained from single furrow measurements results in lower whole field performance than estimated from simulation of the single furrow data (e.g. field RE, AE and distribution uniformity of the root zone up to 26%, 18% and 66% lower than predicted). Field trials were used to demonstrate the ability to estimate whole field infiltration variability, evaluate whole field irrigation performance and optimise whole field irrigation management while taking into account the influence of spatial variability.

This thesis reports research on analysis of the variance of surface electromyogram (sEMG) for healthy participants and people suffering with Lower Back Pain (LBP) when they are walking and running. SEMG signal recorded when the participants were walking and running on a treadmill. The strength and duration of the muscle activity for each heel strike were the features. The results indicate that there was no significant difference in the variance and in the change of variance over time of the amplitude between the two groups when the participants were walking. However when the participants were running, there was a significant difference in the two cohorts. While there was an increase in the total variance over the duration of the exercise for both the groups, the increase in variance of the LBP group was much greater (order of ten times) compared with the participants with healthy backs. The difference between the two groups was also very significant when observing the change of variance over the duration of the exercise. From these results, it is suggested that variance of sEMG of the muscles of the lower back, recorded when the participants are running, can be used to identify LBP patients.

Probing the surface chemistry of thiol ligand binding to cadmium chalcogenide nanoparticles is important to clarify factors involved in quantum dot stability and surface functionalisation. This research is a spectroscopic investigation aimed at gaining a better understanding of the interaction/bonding of various ligands to CdS, with respect to the use of CdS in biological imaging. The findings of this research are important to the more general field of cadmium chalcogenide materials as biological imaging agents. Deposited CdS nanoparticle films were used in this work as model quantum dot surfaces for ligand adsorption studies. The adsorption of the monothiol-containing ligands, mercaptoacetic acid, mercaptopropionic acid, and mercaptoethanol, to CdS thin films were studied in situ using attenuated total reflectance infrared spectroscopy. The absence of an S-H stretch absorption for the adsorbed species showed that adsorption occurred via the deprotonated thiol group. The adsorption of the dithiol-containing ligands α-lipoic acid, dihydrolipoic acid, and dithiothreitol to CdS nanoparticle films was investigated. The adsorption of dihydrolipoic acid and dithiothreitol was found to occur via both thiol functional groups and an additional interaction between the carboxylate group and the CdS surface. The adsorption of α-lipoic acid to CdS in the presence of light proceeded with photo-oxidation of the CdS surface and reductive cleavage of the disulfide bond of α-lipoic acid to produce some adsorbed dihydrolipoic acid and thiosulfate. The adsorption of α-lipoic acid to CdS in the absence of visible light showed no photo-oxidation, and suggested adsorption occurred via retention of the disulfide bond. The kinetics of adsorption and desorption of oxalic acid on deposited anatase TiO₂ films were studied to investigate the feasibility of extracting molecular information from attenuated total reflectance infrared spectroscopic kinetic data of ligand processes on deposited particle films. Oxalic acid adsorbed on anatase TiO₂ is a well-studied example and is reported to result in three different surface species. The profile of the desorption data indicated contributions from three different components. Different component contributions were unable to be obtained from the adsorption data which is attributed to adsorption occurring much faster than desorption and thus being relatively insensitive to the presence of different adsorbed species. The kinetics of adsorption and desorption of mercaptoacetic acid on CdS were investigated. The desorption data profile indicated the presence of two adsorbed species with different affinities for the CdS surface, the exact chemical nature of which can only be speculated upon given the absence of distinguishing IR spectral features. Ligand exchange reactions at the surface of oleate and trioctylphosphine oxide-capped CdS quantum dot films were investigated. Adsorbed oleate was coordinated to the CdS in a chelating bidentate manner through the carboxylate functional group, while adsorbed trioctylphosphine oxide was coordinated though the P=O functional group. Ligand exchange reactions on the oleate and trioctylphosphine-capped CdS films were studied, and exchange with monothiol-containing ligands was observed only at solution pH where the exchanging ligand was uncharged. Avidin-biotin bioconjugation reactions were carried out on CdS films, which involved the sequential adsorption of mercaptoacetic acid, the protein avidin, and the subsequent binding of the ligand biotin. The spectral data suggested that avidin underwent a conformational change upon adsorption to the CdS surface. This conformation appeared to be perturbed again upon binding of biotin, and it is speculated that the conformation partially reverted back to the native solution conformation.

Monolayer protected nanoparticles (MPNs) display fascinating size-dependent electronic, optical and catalytic properties. They are promising candidates to be used as building blocks with which to construct new generation nanoarchitectures and nanodevices for sensing, electronic and optoelectronic applications. The aggregation and dispersion of colloidal nanoparticles is one of the key issues closely related to their potential applications. Our knowledge of the colloid stability of nanoparticle dispersions with small sizes is still in its infancy, however, thymine is one of the bases in DNA, and is a pH sensitive and chromatic molecule. In the present study, thymine-functionalized self-assembled monolayer protected gold nanoparticles were synthesized. Their morphology and surface structure were characterized using TEM, UV-vis, FTIR, DSC-TGA and XPS techniques. The colloid stability of thymine-capped gold nanoparticle dispersions as a function of the type and concentration of monovalent salt, pH and particle size in alkaline aqueous solution were investigated. The manipulation of colloid stability with light was further explored. The results and conclusions are summarized inthis thesis.

In this thesis a model is developed to characterise the behaviour of layered SAW 2- port resonator sensors operating in liquid media. In the critical review of literature, it is found that methods based on the periodic Green's function combined with the COM model are best suited to this task. However, an important deficiency of this approach is the lack of a good model for electrodes buried within layered media. This deficiency is resolved in this thesis by the formulation of a periodic matrix eigen-operator, using a phase-shifted Fourier series representation. This model is then utilised in the study of resonator behaviour as a function of guiding layer thickness, including the mass sensitivity. Based on this modelling work, a SAW resonator structure is designed, and its frequency response is found to be in generally good agreement with theoretical predictions. The mass sensitivity of this device is then analysed using both theoretical and experimental means. In contrast to the sensitivity analyses found in the literature, sensitivity variation across the device surface is considered in this work. For the resonator structure it is found that sensitivity is greatest at the device centre, with the ends of the device making negligible contribution to the complete device response. The result is that the sensitive material may be deposited only in a small region in the centre of the device, with minimal reduction in device response.

Quartz particles of various discrete particle size ranges have been methylated to varying known mounts using trimethylchlorosilane and their flotation behaviour has been assessed in a modification of the Hallimond tube. For each particle size there is a definite degree of. surface coverage below which the particles do not float. A 'flotation domain' is identified which shorvs that both coarse (-100pm) and fine (-10pm) particles require a greater degree of surface coverage to initiate flotation than do intermediate (-40pm) particles. Water contact angles have been measured on quartz plates and powders which have been methylated (under the same conditions) with trimethylchlorosilane. Both advancing and receding water contact angles measured on quartz plates as a function of degree of surface methylationare in good agreement with the angles predicted by the Cassie equation. Advancing water contact angles measured on quartz particles as a function of degree of surface methylation are also in good agreement with angles predicted by the Cassie equation up to surface coverages of'about 70%. The angles measured at higher surface coverages are less than those anticipated by the Cassie equation. The flotation behaviour of the particles has been compared with that predicted by existing flotation theories. It has been shown that coarse particle behaviour is predicted by the kinetic theory of flotation proposed by Schulze. Fine particle behaviour, however, only qualitatively agrees with Scheludko's theory of fine particle behaviour. Calculated induction times, in conjunction with observed flotation behaviour, indicate that the bubble-particle attachment process is most efficient for particles of about 38pm in diameter ander the set experimental conditions used in this study. Flotation rate trials were performed for three particle size ranges and rate constants were evaluated for the various degrees of surface coverage. It was found that the dependence of rate constant on particle size is essentially linear.

Typescript (Photocopy)

<p>The demands on decreased environmental impact from vehicles force the automotive industry to develop engines with reduced engine oil and fuel consumption. Engine oil consumption is recognized to be a significant source of pollutant emissions. Unburned or partially burned oil in the exhaust gases contribute directly to hydrocarbon and particulate emissions. Engine oil and fuel consumption are to a great extend controlled by the topography of the cylinder liner surface.</p><p>Recent engine tests have shown a promising reduction in oil consumption when using cylinder liners with a smoother finish than the current plateau honing.</p><p>One approach to produce smoother liner surfaces is to replace SiC ceramic honing stones with diamond tools. However, event though the diamond honing process results in higher productivity, improved demands of quality control is needed to monitor the degree of cold worked material - “blechmantel” (German), and the resulting risk of increased wear and scuffing.</p><p>A number of petrol and diesel engine cylinder liners have been mapped to be able to verify the quality and consequences, in terms of wear and function, of the honing process. A new mapping method, combining SEM images and quantitative image analysis with traditional 2D profilometry has been developed and tested in this study. The liners where tested in a reciprocating rig of 8 mm stroke and with a frequency of 10 Hz, simulating the top-dead center conditions in a running engine. </p><p>The tests where carried out in high- and low pressure conditions with smooth respectively rough liner roughnesses against PVD coated piston rings. The developed surface mapping method was employed before and after the test to study effect of running-in wear on the surface, features characterized with the SEM- and the 2D profilometer.</p><p>The results show that combining SEM- and profilometric methods gives a good picture of the effects of varying the cylinder liner pressure and roughness. The roughness of the core decreases more for diesel liners than for petrol liners. In average (rough and smooth liners) the diesel core roughness decreases 265% while the petrol liners average on a 60% decrease. Blechmantel- and Irregularities ratio show a high sensitivity to varying conditions and decrease 1180% to 100% for the diesel liners while the parameters increase between 106% to 18% for all the petrol liners. A probable cause is the more severe diesel high pressure run-in conditions are able to effectively “truncate” the plateaux and remove residing plastically deformed un-cut honing residues while the less severe petrol liner conditions not manage to remove the blechmantel and irregularities in an important extent.</p>

<p>The cylinder liners’ surface is really important in an engine because it corresponds with piston rings to a tribologic system indispensable to know for reasons of wear, of oil consumption and engine’s life time. For these reasons, it is important to measure and characterize these surfaces.</p><p>The first part of the project is the observation of the impact of the number of strokes of the plateau honing on the surface of the cylinder liners. It is interesting to observe the impact of the variation of the number of strokes of the plateau honing on the peaks, plateaus and valleys of the surface.</p><p>The second part of the project is the simulation of the oil flow on the surface to observe the links between the roughness parameters and the oil flow and the shear stress.</p><p>The results are interesting, we will observe that the number of strokes of honing as a good impact on the quality of the surface.</p><p>In the second part of the project, the results show a correlation between the machining parameters and the roughness and functional parameters.</p><p>It could be interesting to mix the two parts of the project to see the correlation among machining, roughness and functional parameters for the samples made in the first of the project.</p>