Global behaviour corresponding to the absolute instability of the rotating-disc boundary layer

A study is carried out of the linear global behaviour corresponding to the absolute instability of the rotating-disc boundary layer. It is based on direct numerical simulations of the complete linearized Navier–Stokes equations obtained with the novel velocity–vorticity method described in Davies & Carpenter (2001). As the equations are linear, they become separable with respect to the azimuthal coordinate, $\theta$. This permits us to simulate a single azimuthal mode. Impulse-like excitation is used throughout. This creates disturbances that take the form of wavepackets, initially containing a wide range of frequencies. When the real spatially inhomogeneous flow is approximated by a spatially homogeneous flow (the so-called parallel-flow approximation) the results ofthe simulations are fully in accordance with the theory of Lingwood (1995). If the flow parameters are such that her theory indicates convective behaviour the simulations clearly exhibit the same behaviour. And behaviour fully consistent with absolute instability is always found when the flow parameters lie within the theoretical absolutely unstable region. The numerical simulations of the actual inhomogeneous flow reproduce the behaviour seen in the experimental study of Lingwood (1996). In particular, there is close agreement between simulation and experiment for the ray paths traced out by the leading and trailing edges of the wavepackets. In absolutely unstable regions the short-term behaviour of the simulated disturbances exhibits strong temporal growth and upstream propagation. This is not sustained for longer times, however. The study suggests that convective behaviour eventually dominates at all the Reynolds numbers investigated, even for strongly absolutely unstable regions. Thus the absolute instability of the rotating-disc boundary layer does not produce a linear amplified global mode as observed in many other flows. Instead the absolute instability seems to be associated with transient temporal growth, much like an algebraically growing disturbance. There is no evidence of the absolute instability giving rise to a global oscillator. The maximum growth rates found for the simulated disturbances in the spatially inhomogeneous flow are determined by the convective components and are little different in the absolutely unstable cases from the purely convectively unstable ones. In addition to the study of the global behaviour for the usual rigid-walled rotating disc, we also investigated the effect of replacing an annular region of the disc surface with a compliant wall. It was found that the compliant annulus had the effect of suppressing the transient temporal growth in the inboard (i.e. upstream) absolutely unstable region. As time progressed the upstream influence of the compliant region became more extensive

Production of aluminium matrix composites

Imperial Users onl

New insights into wild deer population genetics, ecology and impacts : implications for management in south eastern Australia

This thesis is a compilation of my own work, driven by my interest into the ecology and impacts of introduced deer in Victoria. My interest in deer initially lead me to undertake an honours project, focussed on deer as a vector for parasites that can affect domestic livestock. During my honours year it became apparent that little was known about the ecology of wild deer throughout south east Australia. My PhD study was therefore developed to fill knowledge gaps of deer ecology, with a focus on developing and optimising ecological tools to generate data to improve deer management strategies. There are many methods available which can be used to collect ecological data on invasive species, such as deer. For my study, I chose methods from four quite discrete fields; global positioning systems (GPS) tracking, population genetics, camera trapping and spatial modelling. These methods were chosen as they are commonly used in ecological studies of invasive species. During my candidature significant attempts were made to deploy GPS collars onto sambar deer to investigate their movement patterns. Movement pattern data is extremely useful and can provide insights into habitat preferences, dispersal ability and other information useful for management. Significant time (around 12 months) was spent applying for ethics approval, gaining relevant approvals, permits and licenses to perform this work as well as performing collaring attempts. Unfortunately all attempts were unsuccessful and the investigation of sambar deer movement patterns had to be abandoned. This highlights the difficulties of working with cryptic deer species inhabiting difficult terrain. The other fields of research pursued (population genetics, camera trapping and spatial modelling) were more successful, the results of which are presented and discussed in this thesis. As the three methods employed in this study are taken from very different fields, a number of experts were enlisted to guide the respective data chapters. The population genetic studies (Chapters two and three) were guided by my primary supervisor Dr Fiona Hogan. I conducted all scat collections from across Victoria, including French Island and Mount Cole and performed all DNA isolations (over 300 in total). Population structure analysis for chapter three was undertaken with the assistance of Dr Faye Wedrowicz and Dr Carlo Pacioni. The camera trapping study (Chapter four) involved deploying camera traps in Baw Baw National Park, which I conducted myself. Occupancy and detectability data analysis for chapter four was performed with the assistance of Dr Hugh Davies. Spatial modelling (Chapter five) which focussed on modelling deer-vehicle collision risk across Victoria was directed by Dr Casey Visintin. Chapter’s two to five are written as independent scientific publications, therefore there is some unavoidable repetition within the thesis as a whole. Minor changes have been made to the formatting of the published papers to keep style consistent within the thesis.Doctor of Philosoph

JOHN HOYLAND: THE MAKING AND SUSTAINING OF A CAREER - 1960-82

Full version unavailable due to 3rd party copyright restrictions.The thesis explores the making and sustaining of the career of the English abstract artist, John Hoyland from his inclusion in the seminal Situation exhibition of 1960 to his winning the John Moores First (Purchase Prize) in 1982. It investigates the institutional and critical contexts that supported Hoyland’s rise to prominence in the 1960s and situates him within the art world of the time: its galleries, exhibitions, advocates, dealers, critics, patrons and collectors (public and private). It notes the improvements to the art infrastructure in the United Kingdom and assesses whether these improvements had any impact on Hoyland’s career. Careful analytical attention is paid to the work of John Hoyland and how his work was presented to numerous audiences and critically received. Hoyland’s career is considered in relation to the changes in art practice both in the United Kingdom and the United States during these two decades, and the challenges that these changes in practice and fashion through up, The thesis examines John Hoyland’s early career with these critical and institutional contexts in mind. It considers the challenges he faced throughout the 1970s to sustain a professional career and offers reasons to explain why his trajectory towards professional success was neither smooth nor consistent. The thesis explores the correlation between art production, art markets, critical reception and acclaim, and commercial success. The fundamental question that this thesis seeks to answer is whether whatever recognition Hoyland’s work received was solely because of its quality or whether there is an element of Hoyland being buoyed up by the system and promoted with more enthusiasm than was merited - as American critics suggested – and thus being to some extent a product of these institutional forces. The mapping and analysis of John Hoyland’s early career contributes to similar inquiries concerning how careers are made and sustained in the visual arts. The thesis works with the established models used to explore this process and offers some adaptations of them

On group-based trajectory modelling

Group-based trajectory models are used for characteristics that, when followed longitudinally, may show subpopulations with distinct trajectories. This thesis describes three studies I undertook relating to these models. Group-based trajectory models generally assume a certain structure in the covariances between measurements, for example conditional independence, homogeneous variance between groups, or stationary variance over time. Violations of these assumptions may result in poor model performance, but the extent and nature of this is not well understood. In the first study, I used simulation to investigate the effect of covariance misspecification on misclassification of trajectories in commonly used models under a range of scenarios. I found that the more complex models generally performed better over a range of scenarios. In particular, incorrectly specified co- variance matrices could significantly bias the results, whereas using models with a correct but more complicated than necessary covariance matrix incurred little cost. An underlying assumption of the group-based trajectory model is that it applies to all trajectories, and this does not allow for the possibility that outliers may be present. Thus outlying trajectories may distort the estimated groups of these models and any subsequent analyses that use them. In the second study, I used simulations to assess the impact of outliers on group-based trajectory models. The presence of outliers tended to lead to an increased number of groups, and a reduction in the correct classification rate provided the group means were well separated. Following the simulations, I developed an algorithm for identifying outlying trajectories, and evaluated its performance on the simulated trajectory datasets. The application of my algorithm is recommended as part of sensitivity analyses to determine the effect that outliers may have. One approach to modelling the influence of prior covariates in the group-based setting is to consider models wherein these covariates affect the group member- ship probabilities. In the third study, I compared six different methods from the literature for estimating the effect of covariates in this way. I found that when investigating the effects of covariates, the full likelihood approach minimised the bias in the estimates of the covariate effects. In this ‘1-step’ approach, the estimation of the effect of covariates and the trajectory model are carried out simultaneously. Of the ‘3-step’ approaches, where the the effect of the covariates are assessed subsequent to the estimation of the group-based trajectory model, only Vermunt’s Improved 3-step resulted in bias estimates similar in size to the full likelihood approach. The remaining methods resulted in considerably higher bias in the covariate effect estimates, and should not be used. This thesis provides guidance in the use of group-based trajectory models for practising statisticians, focusing on the choice of covariance structures, the impact and identification of outlying trajectories, and the most appropriate methods for estimating the effects of covariates. Researchers should consider a wide range of models, and bearing in mind the assumptions they make, carefully choose that which fits best with the data.Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Mathematical Sciences, 201

A Theoretical Relationship Between Guardianship and Techniques of Neutralization: A Qualitative Analysis of Digital Piracy

This research is a qualitative analysis of digital piracy at the height of Napster in 1999. The findings support the notion that technology has given rise to several new techniques of neutralization. In some cases these techniques are completely new and in others they are 21st century updates to traditional techniques. Furthermore, this research uses forum posts from USENET to determine that guardianship as created by Cohen and Felson\u27s Routine Activities Theory is uniquely connected to neutralization based on two unique guardianship qualities, authority and capacity

Cosmology with weak lensing voids and peaks

The goal of modern cosmology is to measure cosmological parameters as accurately and precisely as possible, with future stage-IV surveys aiming to achieve this at the sub-percent level. To maximise the utility of such surveys, we must develop methods that can more fully capture the wealth of cosmological information contained within the data. In this thesis, I develop new weak gravitational lensing statistics as a means to achieve this. To this end, I study in detail the properties of weak lensing voids and peaks. First, I establish weak lensing voids as a new statistic that corresponds to extended underdense regions of convergence maps, and show that they offer several advantages over galaxy voids, including larger lensing profile amplitudes. I then study a range of void finders to test the impact of the void definition on the resulting weak lensing void properties, and identify the tunnel algorithm as the most promising void finder. This is followed by wCDM parameter forecasts from an LSST-like survey for weak lensing voids, which shows that they perform better than the standard shear two-point correlation function. I then show that weak lensing voids also have higher sensitivity to modified gravity theories than galaxy voids. Next, I study the clustering of weak lensing peaks and present simple scaling relations for their two-point correlation function. I then make similar parameter forecasts for the peak two-point correlation function, and show that when combined with the peak abundance, peaks can give tighter constraints than the shear two-point correlation function. Finally, both the void and peak statistics presented in this thesis offer complementary parameter degeneracy directions to the shear two-point correlation function. This makes these statistics invaluable for cosmological parameter measurements from ongoing and future weak lensing surveys

Dismantling Bodies: The War on Terror, and the Wound Aesthetic of \u3cem\u3eCSI: Crime Scene Investigation (2000-2015)\u3c/em\u3e

This paper interrogates the aesthetic signature of CSI: Crime Scene Investigation (2000-2015). Utilizing a selection of representative episodes airing during George W. Bush’s first term, I analyze how CSI mobilizes a particular aesthetic of wounding in which wound sites,bodily and geographic, may be understood to serve as vulnerable apertures through which underlying threads of critical engagement with the direction of the 9/11 discourse may be aspirated from within the body of the text. Specifically, I approach the wound sites of CSI as sources of war-on-terror critique that serve political double-duty. On the one hand, CSI’s injury-centric narratives and accompanying wound aesthetic provide a canvas against which the traumatizing realities of 9/11 could be mediated and moderated for a newly death-anxious audience. On the other hand, the wound aesthetic ironically provides a recuperative narrative about the state’s ability to respond to political violence and prosecute its perpetrators

Investigation of the thermo-hygro-chemico-mechanical performance of the Bentonite barrier at the high-level radioactive waste canister interface

PhD ThesisThis research focuses specifically on the geotechnical and physicochemical evolution of the highly-compacted Bentonite at the radioactive waste canister interface, with respect to the multi-barrier system for deep geological disposal of radioactive waste. The research investigated the geomechanical (i.e. Swelling pressure, self-healing, permeability and rheology) and mineralogical (i.e. Fe enrichment/ integration into the aluminosilicate structure and alteration to the accessory minerals) evolution of the Bentonite barrier under key life phases of the near-field regarding thermo-hygro-mechanical-chemico factors. Such life phases were derived from leading concepts and were simplified into three fundamental stages replicating key stages of the near-field. The first phase was “early-life” replication where high temperatures/ drying conditions were exposed to the interface. The second phase replicated the “mid-life” conditions, subjecting the interface to resaturation using high saline ground water with high temperatures but lower than the initial thermal exposure. The final phase replicated the “late-life” conditions which subject the interface to background thermal loading, representative of background temperatures of a crystalline host rock, with a completely saturated/ hydrostatic saline pore-water environment. Post analysis examined the impact on the geomechanical and physicochemical properties with respect to how these relate to the desired functionality of the passive barrier system. Previous work has seldom addressed this interface system from a coupled engineering and physicochemical perspective. A comprehensive investigation looking at how the near-field environment inhibits the desired engineering function and the related physicochemical state will enable insight into building a UK specific safety case. This research employed an experimental approach exploring the boundary conditions that the interface would experience as inferred from leading international radioactive waste repository concepts. Experimental methods included batch testing, interface replication and geotechnical constant volume tests. Batch tests looked at a mix of variable boundary conditions relevant to the near-field interface environment and isolated specific conditions to measure the intrinsic alterations to the desired engineering function. Interface replication tests subject MX-80 Bentonite, compacted to in-situ emplacement conditions, and carbon steel to an interface environment under three separate “life-phases” (as stated earlier) to assess what phase had the most significant impact on the geomechanical and physicochemical state of the barrier. Finally, the constant volume experiments subject oedometer samples to “mid-life” conditions as well as isolated “mid-life” variables respectively. Post exposure measurements looked at the impact of the various “mid-life” boundary conditions and their associated impact on the swelling pressure, swelling kinetics, permeability and rheology. “Mid-life” conditions were chosen to carry forward into the oedometric tests as this phase was considered to subject the Bentonite to the highest thermal loading under the most complex chemical environment. This work has highlighted key near-field factors that alter the interface barrier function after relatively short-term exposure. Such as thermal loading and exposure to high salinity, both induce alterations to the swelling pressure, swelling kinetics and rheological properties. It was observed that high temperature-saline exposure caused loss in the dielectric constant and reduction in the Diffuse Double Layer (DDL), as well as the dissolution/ precipitation of silica which inhibited the swelling and plasticity of the MX-80. Exposure to corrosion products derived from S275 carbon steel appear not to significantly affect the physical properties of the Bentonite compared to thermal and saline factors after short-term experimental contact. However, corrosion integrated into the Bentonite matrix after thermal loading in the presence of Deionised (DI) water displayed a slight increase in the kinetic behaviour. This was concluded to be due to the high volumetric capacity of the hydrated corrosion products within the clay matrix. Furthermore, interface tests indicate some alteration to Ferro-saponite type smectites, indicating some Fe integration into the octahedral layer resulting in a trioctahedral smectite. The outer zone furthest away from the canister was characteristic to Mg-type saponite. Nonetheless, XRD displayed that the clay component remained high charge smectite with no alteration to the d-spacing after swelling. Green rust and Goethite was observed at the interface and mid zones respectively, the ferrous mineral appeared to be meta-stable when exposed to ambient conditions. Physicochemical analysis indicated the presence of ferrous hydroxides complexed to the edge sites of the clay. High diffusion rates and dissolution rates of iron corrosion and secondary minerals respectively were greater in “mid-life” and “late-life” conditions. This indicates that thermal loading, as well as a high saline hydraulic gradient, aided the corrosion process and displacement of interlayer cations away from the corrosion rich zone. This resulted in the development of a high pH environment which ultimately increased dissolution rates of the secondary minerals. The dissolution of silica minerals induced precipitation of siliceous by-products upon cooling which essentially “fused” clay particles together, ultimately inhibiting the macro swelling properties and ductility. Results show that the macro-scale geomechanical properties of the Bentonite do not deviate below the design limits set out by leading concepts, but do come close to the minimum limits for swelling pressure (1 – 2MPa). Concern is however highlighted for combined thermo-saline-chemical exposure, which appears to cause significant loss in the ductility of the MX-80. This may be disadvantageous to the stress distribution around the canister which is necessary to ensure that the canister is not breeched due to potential rock displacements etc. Neither comparative data, nor design limits were set out for barrier stiffness, therefore the study suggests that high thermal exposure and duration is kept to an absolute minimum. The research has further highlighted the need to investigate the impact of a completely reduced iron-rich environment on the engineering function of the Bentonite barrier, as completely reduced conditions were difficult to obtain within the time-scale of this study. Other research suggests that a rich environment would accelerate clay alteration as well as alterations to layer charge and lattice stresses potentially inducing 2:1 to 1:1 alteration, all of which potentially lead to complete loss in the swelling behaviour of the clay

Customer satisfaction within education – the application of an integrated curriculum design method

The post-16 stage of education is critical in securing and developing people entering engineering professions and related occupations. Engineering employers and employees alike have however highlighted problems regarding poorly designed curricula failing to prepare employees for industrial and commercial roles. The premise of this thesis is that the issue confronting education is one of quality management. Curriculum designers must know how to anticipate and understand customer requirements and practically translate these requirements into a deliverable curriculum package. The aim of this research is to realise the synergy of curriculum design and TQM by developing a theoretical integrated curriculum design method. Synergies between TQM and traditional curriculum design methods are investigated and an integrated curriculum design method based on the use of PDCA and incorporating a two-phase modified use of QFD is hypothesised and justified. Subsequently, application of the curriculum design method is completed in relation to a number of selected engineering companies within the South Wales region and an appropriate curriculum proposal, for the provision of engineering education within the 16-18 year age group is produced. The proposal has been constructed with characteristics complementary to the competencies required by these companies and incorporates the most suitable teaching, learning and assessment methods to maximise the development of the students. This is valuable information for those concerned