14,468 results for Doctoral

  • Fusion systems of finite alternating groups

    Nectoux, Antoine (2015)

    Doctoral thesis
    The University of Auckland Library

    It is generally accepted that the theory of fusion systems began with Alperin’s Fusion Theorem [1]. Alperin’s result was improved by Goldschmidt [14] and by Puig [23]. The final result, known as the Alperin-Goldschmidt Fusion Theorem, states that the fusion of certain non-trivial subgroups, namely essential p-subgroups, controls the fusion of a finite group. The axiomatic foundations of fusion systems were developed by Puig [24] during the 1990s. His work underpins the construction of fusion systems of blocks of finite groups. An and Dietrich classified the essential p-subgroups of some classical groups [4], sporadic simple groups [5] and finite symmetric groups [6]. In this thesis, we investigate a correspondence between the essential p-subgroups of a finite symmetric group and those of the corresponding alternating group. Of particular interest is the case p = 2: a finite symmetric group and its associated alternating group have di erent Sylow 2-subgroups. The odd case is relatively clear. Similarly, we establish a correspondence between the essential p-subgroups of a finite group and the essential p-subgroups of a 2-covering group, for an odd prime p. However, in the case p = 2 there is no such correspondence. In many cases the fusion system of a block of a finite group is equivalent to the fusion system of some finite group (possibly di erent). It is not known whether this is the case for the fusion system of a block of a finite alternating group. We investigate a correspondence between the essential p-subgroups of a fusion system of a block of an alternating group, and the essential p-subgroups of a fusion system of an alternating group (possibly di erent). Once again, if p is odd, then this correspondence is clear. If p = 2, then a special case arises.

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  • Biomimetic Design and Experimental Methods Towards a Biologically Inspired, Soft Bodied, Peristaltic, Esophageal Swallowing Robot

    Dirven, Steven (2015)

    Doctoral thesis
    The University of Auckland Library

    Natural and biological phenomena continue to be a strong source of inspiration in the robotics eld, as scientists and engineers aim to solve synonymous problems. The capabilities of traditional robots have seen signi cant development, where a new frontier into more soft and compliant actuation and sensation structures has seen recent exploration and the emergence of a new branch of research: soft-robotics. The intrinsic nature of these new technologies is that they are capable of soft and continuous interaction with their environment, which facilitates new actuation, transport, and locomotion modes. The main aim of this research initiative was to develop complementary actuation and sensation technologies, inspired by the esophageal phase of swallowing in man, to replicate biological swallowing. It is motivated by the di ering swallow capability of individuals, to understand swallow e cacy as a symptom mitigation method for patients su ering from dysphagia, di culty with safe swallowing. The peristaltic transport process in the esophagus has been previously investigated by a range of medical, mathematical, food scienti c, and engineering methods. However, each of these techniques has their own unique caveats. The processes of abstraction, speci cation, and subsequent conceptual development of a physical swallowing system external to the human body have taken these limitations as a set of input constraints. The swallowing robot and sensation technologies embody the interdisciplinary knowledge in this eld, and facilitate a complementary physical evaluation technique to augment and support the alternative avenues of investigation. This thesis examines the methods towards delivery of a soft, biomimetic, peristaltic, swallowing robot, consisting of actuation, trajectory generation, and sensation elements, to achieve clinically signi cant swallowing trajectories for the purpose of physical food bolus investigation external to the human body. By demonstrating the capability of these systems independently, and in their integrated nal state, the research provides a unique platform for biomimetic swallowing that brings the diverse knowledge from the medical, mathematical, food science, and engineering elds together. It presents new opportunities to investigate the relationships between these domains, towards developing foods, which exhibit intrinsic swallow safety in man.

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  • Integration of gas instantaneous auxiliaries with renewable energy residential water heaters

    Bourke, Grant (2015)

    Doctoral thesis
    The University of Auckland Library

    Gas instantaneous water heaters are increasingly used as auxiliary energy sources for renewable energy domestic hot water systems. Currently the gas used by these systems is measured and modelled only very approximately. Accurately assessing consumption is important as gas can supply up to 50% of the energy. Gas auxiliaries used in these arrangements are also predominantly designed as stand-alone devices and typically integrated into renewable systems in a very basic manner. This research seeks to fill two important gaps. First, how does the gas instantaneous water heater actually perform as part of a renewable water heater? Second, once performance can be measured and modelled accurately, what improvements in energy use might be made through novel ways of integrating the gas auxiliary with the renewable energy water heater? This study adopts a broad approach in examining these gaps. A number of existing test methods for gas instantaneous, air source heat pump, solar and electric storage water heaters are reviewed in detail. A number of different gas instantaneous water heater test standards are compared experimentally. The effect of water use patterns on the energy use of various water heating technologies is investigated both experimentally and with modelling. The carbon emissions of a number of different types of water heater is calculated after a detailed review of CO2 emissions of the New Zealand electricity generating system during both dry and wet years. A new experimental test method is developed to characterise the steady state performance of a gas instantaneous water heater. This performance characterisation is then used in a TRNSYS model together with established models of renewable energy water heaters to predict energy consumption. Integrated systems using novel control and hydraulic connection arrangements are then compared to other water heating systems. The current methods of determining the gas consumption of auxiliary water heaters may understate energy use by as much as 15%. Improved control system integration saves an average of 17% in energy and 11% in carbon dioxide emissions compared to other high efficiency water heating systems. Improved hydraulic arrangements result in 4.5% savings. The change in energy conversion ratio with differing water use patterns of some water heaters can exceed the differences exhibited between technology types and competing models of similar technology. If consumers are to choose their water heaters based on comparable running costs or emissions, accurate measurement and modelling of gas auxiliaries is required. Current test methods do not appear to provide the required accuracy. There are also opportunities for significant improvement in energy use through better integration of gas auxiliaries with renewable energy residential water heating systems.

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  • Stochastic Boundary Operators and Model Uncertainties in Electrical Impedance Tomography

    Hadwin, Paul (2015)

    Doctoral thesis
    The University of Auckland Library

    Electrical impedance tomography (EIT) is an imaging modality which can be applied to conductive targets. In EIT electrodes are placed on the boundary, or surface, of an object and weak electrical currents are injected into the target through the electrodes. The resulting voltages are measured and an estimate for the internal conductivity distribution of the target is computed. There are numerous applications of EIT, from monitoring a patient's pulmonary or brain function to imaging of multi-phase flows or subsurface geophysical structures. The difficulty in EIT, as with all di use tomography modalities, is that the estimation of the internal conductivity distribution is an ill-posed inverse problem. This implies that the estimates are unstable and often non-unique. As a consequence, attention must be paid to the mathematical modelling of the measurements as well as to the estimation methods. Furthermore, in any practical situation where a mathematical model is applied there are parameters which are unknown or uncertain. In order to handle these uncertainties simplifying assumptions or approximations are usually made. These approximations for the modelling uncertainties are typically made since the information is impossible or infeasible to measure. Failing to account for these modelling uncertainties leads to systematic errors, which destroy estimates. Moreover, in practical situations there is limited computational power and time so there is pressure to compute the estimates with a approximative model. A typical way of reducing the computational cost is to shrink the computational domain in which estimates are computed. For example, in geophysical EIT the region of interest may only be very small in comparison to the area where the current ows resulting from the EIT current injections can stretch. If these current ows are not correctly modelled, estimates of the conductivity distribution may have severe artefacts rendering estimate meaningless. In this thesis, we develop a computationally feasible model for practical absolute EIT imaging. Such a model will have to account for the modelling uncertainties which are present in all practical measurements. Also it will have to be suffsaintlyy low dimensional so that the online computation of the conductivity estimates is feasible. In order to achieve this, we develop a model which accounts for the current ows when the computational domain is truncated. The resulting domain truncation model involves the stochastic Dirichlet-to-Neuman operator over the truncation boundary. The Karhunen- Lo eve decomposition is then adapted to give a low-dimensional model for the stochastic Dirichlet-to-Neumann operator. In order to take the modelling errors into account, we use the recently developed Bayesian approximation error approach. In particular, we use the Bayesian approximation error approach to compensate for errors induced from unknown contact impedances, model reduction and the use of an approximative domain shape.

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  • Essays on Return Predictability

    Lu, Helen (2013-08-21)

    Doctoral thesis
    The University of Auckland Library

    This dissertation is a collection of three essays that investigate the momentum effect and the short-run predictability in currency carry trade profits. The first essay investigates whether tail risks of momentum strategies make them unattractive within the context of prospect utility. Momentum returns have strongly asymmetric tail risks and that asymmetric tail risk is precisely what makes momentum strategies unattractive. This study is the first to document the undesirable tail risk characteristics of momentum returns. The second essay uncovers economically significant predictability in carry trade profits from shorting the low-yielding currencies. The monthly world equity index return, monthly changes in currency volatility and monthly changes in equity volatility predict carry trade profits from the short leg two months later, while monthly changes in commodity prices, monthly changes in currency volatility and monthly changes in equity volatility predict carry trade profits from the long leg three months later. Investors could have used the discovered leg-specific predictability to time the market and improve their trading outcomes, instead of staying fully invested or predicting carry trade profits from both legs with a single model. Evidence from two tests conducted in this essay points towards the gradual information diffusion model as the most likely explanation for the discovered predictability, while time varying risk premia do not seem to explain this effect. The last essay examines return predictability among carry trades, stocks and commodities in a dynamic vector auto regression setting. The predictive effect goes from commodities to stock, from stocks to low-yielding currencies and from commodities to high-yielding currencies. Variables in these markets are more strongly correlated in the high-risk regime than in the low-risk regime. Drops in the world equity index (commodity prices), but not rises, predict decreases in carry trade profits from low-yielding (high-yielding) currencies. Increases in currency volatility, but not decreases, predict drops in carry trade profits from low-yielding currencies. The in-sample asymmetric effects also exist out-of-sample, but these asymmetric prediction models do not consistently deliver better forecasts than symmetric models.

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  • Influences of human behaviour on energy efficiency in commercial buildings

    Mokhtar Azizi, Nurul (2015)

    Doctoral thesis
    The University of Auckland Library

    Green building was introduced to reduce energy consumption and minimise the adverse impact to the environment. This research attempts to understand the behaviour of building occupants and its implication towards energy saving. With better understanding of the building occupants’ behaviour, building management strategies can be efficiently improved. A comparative case study approach was adopted, along with mixed method for data collection and analysis. Three buildings in Malaysia and five buildings in New Zealand were selected as the research case study. The analysis shows that occupants in the green buildings practice better energy saving than those in the conventional buildings. Better energy management strategies have been implemented in the green buildings as compared to the conventional buildings. These have been proven to encourage the building occupants to save energy. Although results showed that the energy management strategies and the design features in green buildings promote occupants to save energy, yet these did not motivate the building occupants to save energy. This study has contributed to the existing body of knowledge by providing an understanding of the relationship between occupants’ behaviour and buildings energy efficiency. As a result, energy management strategies can be developed in order to increase the occupants’ level of practice in saving energy. This research has also provided useful information on the occupants’ level of interaction with the building control system. Findings revealed that green building design is not the only contributing factor in energy reduction. The need for the building occupants to practice green behaviour is equally important. This is possible through engagement of occupants’ behavioural modifications.

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  • Performing the Revolution: Socialist Realism and Its Heterogeneity in the Model Performances

    Kong, Ruicai (2015)

    Doctoral thesis
    The University of Auckland Library

    This study investigates heterogeneity in the representation of the theme of revolution in the model performances (样板戏) within the aesthetic framework of Socialist Realism. This thesis argues that understanding the theme of revolution in the model performances should be, first and foremost, mediated by Socialist Realism, which involves heterogeneous discourses that contaminate the purity of ideology. Through a rigorous critique of Socialist Realism, this study offers an aesthetic approach to the socialist culture of the Maoist era. Four grand aesthetic trajectories of Socialist Realism are explored with regard to the representation of revolution: a) the representation of reality in the modern Peking opera Shajiabang, b) the trope of light in the Peking opera The Red Lantern, c) temporality, or the representation of ―the present‖ in the Peking opera Song of the Dragon River and d) optimism, and the visuality of the female body in the socialist ballets The White-haired Girl and The Red Detachment of Women. These heterogeneous discourses are shown to be closely conflated with the essential tenets of Socialist Realism, and as such to eventually contaminate and transform them. They manifest themselves in various ways, ranging from jianghu ambience in Shajiabang, a Confucian mode of affection in The Red Lantern, the temporality of the past in Song of the Dragon River, to uncanny visuality in the two socialist ballets. Since the theme of revolution in all these works is mediated by the aesthetic of Socialist Realism, the ideology of revolution is thus diluted and subject to other, heterogeneous, aesthetic doctrines. The theme of revolution represented in the model performances appears plural, unstable, and, more importantly, impure. This examination of Socialist Realism and its heterogeneity, as manifested in the model performances, sheds new light on the complexity and ambiguity of Maoist culture and furthers our reflection on its revolutionary legacy.

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  • Understanding Individuals who Access Sexualised Images of Children

    Morgan, Sian (2015)

    Doctoral thesis
    The University of Auckland Library

    The number of detected child sexual abuse imagery (CSAI) users has increased dramatically over the last decade (Babchishin, Hanson, & VanZuylen, 2014; Wolak, 2011). Despite the relevance to today’s society it still remains unclear what factors are associated with accessing CSAI. In particular, research regarding the early life development and characteristics of this group of offenders is underdeveloped and only recently have researchers begun to develop typologies of those who access CSAI (e.g., Houtepen, Sijtsema & Bogaerts, 2014). Similarly, the development of tools to effectively assess and treat internet sexual offenders is notably lacking (Perkins & Merdian, 2014). The present study had two primary aims. Firstly, to contribute to the current understanding of what may contribute to individuals accessing sexualised images of children. This included gathering rich descriptions of participants’ early life experiences and the period leading up to their first offense. The second aim was to contribute to the development of therapy through gaining insight into client’s perspectives of what they found helpful in treatment. Twelve men currently or recently involved in prison or community treatment programmes were interviewed and the transcripts were analysed using thematic analysis (Braun & Clarke, 2006). The key themes identified from the data around development included difficulties in early family life, negative school experiences, difficult sexual development and difficult intimate relationships. In terms of what precipitated offending, key themes included stress, progression from other legal material, loneliness and isolation and spare time, coping with negative emotions, addiction, collecting and denial were all identified as maintaining factors. These findings were comparable to previous, similar qualitative research (Sheehan & Sullivan’s, 2014) and Ward and Siegert’s (2002) Pathways Model. Key themes from the data around the helpful aspects of treatment experiences were consistent with previous literature regarding sexual offender treatment more broadly. These themes included developing an understanding of offending, working in a group, a safe environment and attributes of the therapist. The suggestion made by participants of continued support after the programme parallels previous research which suggests that continued monitoring of sexual offenders can have a positive impact on reoffending (Elliott, Findlater & Hughes, 2010).

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  • Topics in Generalised Inverse Limits

    Lockyer, Michael (2014)

    Doctoral thesis
    The University of Auckland Library

    Generalised inverse limits are a new topic of study in the area of continuum theory. Although similarly defined to the more traditional inverse limits of continuous functions on continua, they have a much richer structure. It was realised early on that many of the theorems relating to the inverse limits of continuous functions do not carry over to generalised inverse limits, which use set valued functions. Much of the research in generalised inverse limits to this point has been to attempt to characterise their structure. This thesis contains three main chapters, each of which is based on a topic in generalised inverse limits research. In the first of these we explore the structure of a particular generalised inverse limit known as K(0,1). This is the inverse limit of a generalised tent map. The inverse limits of tent maps have played an important role in continuum theory in the past, and with the introduction of generalised inverse limits we can include generalised tent maps that are not continuous functions. The only such generalised tent map whose inverse limit does not have a very simple structure is K(0,1). In this chapter we prove a number of topological properties of K(0,1), and give an embedding of K(0,1) into R3. For the second topic we characterise a certain kind of disconnection in generalised inverse limits over Hausdor↵ continua. This generalises a result by Greenwood and Kennedy for generalised inverse limits over intervals. Connectedness is a property that has attracted much interest in generalised inverse limits, as these are not necessarily connected, unlike the inverse limits of continuous functions, which are. In the final chapter we prove a result relating to path connectedness in generalised inverse limits. Path connectedness in generalised inverse limits is in some ways a very di↵erent property to connectedness. For example, a generalised inverse limit may not be path connected even though all its finite approximants are path connected. This cannot happen if we replace the words “path connected” with “connected” in the previous sentence. The result proved in this chapter links the path connectedness of a generalised inverse limit with path connected properties of its finite approximants.

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  • A Steady State Model of Fluid Flow in Airways

    Sharp, Katie (2015)

    Doctoral thesis
    The University of Auckland Library

    The genetic disease cystic fibrosis (CF) is a mutation in the cystic fibrosis transmembrane conductance regulator (CFTR) gene, and results in viscous mucus and impaired mucociliary clearance leading to chronic recurring pulmonary infections. Although extensive experimental research has been conducted over the last few decades, CF lung pathophysiology remains controversial. There are two competing explanations for the observed depletion of periciliary liquid (PCL) in CF conditions. The volume hypothesis assumes fluid hyperabsorption through surface epithelia due to an over-active Epithelial Na+ Channel (ENaC), and the low secretion hypothesis assumes inspissated mucins secreted from glands due to lack of serous fluid secreted from gland acini. We develop a spatial mathematical model that reflects in vivo fluid recycling via submucosal gland (SMG) secretion, and absorption through surface epithelia. We test the model in CF conditions by increasing ENaC open probability and decreasing SMG flux whilst simultaneously reducing CFTR open probability. Increasing ENaC activity only results in increased fluid absorption across surface epithelia, as seen in in vitro experiments. However, combining potential CF mechanisms results in markedly less fluid absorbed while providing the largest reduction in PCL volume, suggesting that a compromise in gland fluid secretion dominates over increased ENaC activity to deplete the serous fluid above CF surface epithelia in vivo. Model results also indicate that a spatial model is necessary for an accurate calculation of total fluid transport, as the effects of spatial gradients can be severe, particularly in close proximity to the SMG.

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  • Prosody in typical and clinical populations: Children and adults with hearing loss

    Kalathottukaren, Rose (2015)

    Doctoral thesis
    The University of Auckland Library

    Aims: Aims of this doctoral thesis were to: 1) evaluate published tools for assessing prosodic skills in children and adults, 2) investigate age effects on different aspects of prosody perception in typically developing children and report normative performance for New Zealand-English speaking 7-12 year olds, 3) compare prosody perception and production in children with hearing loss and age- and gender-matched children with normal hearing, 4) examine the effects of age, hearing level, and musicality on children’s prosody perception, and 5) investigate prosody perception and musical pitch discrimination in adults using cochlear implants. Methods: Published tools were identified through searching online databases, bibliographies of relevant articles and contacting authors. Six receptive subtests of Profiling Elements of Prosody in Speech-Communication (PEPS-C) and Child Paralanguage and Adult Paralanguage subtests of Diagnostic Analysis of Non Verbal Accuracy 2 (DANVA 2) were used as prosody perception measures. Musical pitch discrimination was assessed using Contour and Interval subtests of the Montreal Battery of Evaluation of Amusia (MBEA). Prosody productions were rated using the perceptual prosody rating scales. Results: The literature review identified nine prosody assessment tools available for use with children and adults that were appraised for their intended purpose, target population, domains of prosody assessed, feasibility, and psychometric properties. The review highlighted the need to continue to develop and test tools for effective and comprehensive assessment of prosodic skills. The second study revealed that prosodic competence develops significantly between the ages of 7 and 11 years. Results from the PEPS-C test revealed a differential pattern of acquisition for different aspects of prosody, with 7-8 year olds being significantly poorer than 11-12 year olds on Chunking and Contrastive Stress subtests. Performance on the DANVA 2 test of affective prosody perception differed significantly across emotional categories (angry > happy > sad > fearful) and the level of emotion intensity (better scores for high emotion intensity items). The third study showed that children with hearing loss aged 7 to 12 years performed significantly poorer than controls on PEPS-C and DANVA 2 tests. Prosody perception scores were significantly correlated with age, hearing level, and musicality. Prosody production evaluated using perceptual rating scales showed greater variation in perceptual ratings of pitch, pitch variation, and overall prosody in the hearing loss group compared to the control group. Adults using cochlear implants performed significantly poorer than adult normative values reported for PEPS-C and DANVA 2 tests and the majority performed at chance on MBEA tasks. Conclusions: The relatively small number of tools available to evaluate prosody compared to other aspects of language suggests that prosody is often overlooked in terms of formal language assessment. The normative results reported for New Zealand-English speaking children will be useful when assessing prosodic difficulties in children with hearing loss or autism spectrum disorder. Together, the studies on children and adults with hearing loss suggest that clinical assessment and therapy services for people with hearing loss should be expanded to target prosodic difficulties.

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  • The Geometry of Isochrons in Planar Systems

    Langfield, Peter (2015)

    Doctoral thesis
    The University of Auckland Library

    Probing the response of an oscillator to a perturbation is an important tool for understanding the underlying dynamics of the oscillator. Mathematically, we can determine these responses by finding the so-called isochrons of the underlying periodic orbit. Each isochron is the set of points that converge to the periodic orbit in phase with each other. In this thesis, we investigate planar systems, for which isochrons are curves that can have very complex geometries; we study how these complexities arise. We start by considering the isochrons of a periodic orbit in the FitzHugh-Nagumo system, an example from the 1970s of a system with two time scales for which the overall structure of the isochrons could not be determined with the computational methods of that time. We show, via numerical continuation, that the isochrons exhibit extreme sensitivity and feature sharp turns. We observe that the sharp turns and sensitivity of the isochrons are associated with the slow-fast nature of the FitzHugh-Nagumo system; more specifically, they occur near a repelling (unstable) slow manifold. In order to characterise such sharp turns, we introduce the notion of backward-time isochrons and also extend the concept of an isochron to isochrons of a focus equilibrium. The backward-time isochrons are isochrons of the reversed-time system, and by considering their interaction with the forward-time isochrons, we are able to identify a new bifurcation: a cubic tangency of curves, which gives rise to non-transverse intersections between forward-time and backward-time isochrons. We call this bifurcation a cubic isochron foliation tangency, or CIFT bifurcation. It is not a local feature but happens along trajectories in the annulus where both sets of isochrons coexist. We construct and discuss examples of three mechanisms for a CIFT bifurcation: a global time-scale separation; a perturbation that increases the velocity along trajectories in a local region of phase space; and a canard explosion (in the Van der Pol system). Finally, we present our method for computing isochrons of periodic orbits and focus equilibria, and a novel approach for computing phase response curves, which is accurate for any size of the perturbation.

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  • Using Information Technology to Enforce Management Controls in New Product Development Processes: Fishing for Innovative New Products

    Liew, Angela (2015)

    Doctoral thesis
    The University of Auckland Library

    Appropriate use of management controls can assist and constrain individuals depending on the circumstances. Information technology has the potential to contribute significantly to the operation and application of management controls if the management control structures have been designed to leverage the capabilities of information technology. This is the case for new product development where many individuals from a mixed hierarchical level are involved. Through a case study, this thesis looks at how senior management changed in their decision-making behaviours and how employees changed their behaviours towards task-completion after the implementation of information technology. Initially, senior management had not anticipated that the use of information technology would expose them to scrutiny by their superior, peers and subordinates. However, this scrutiny steered them to become more circumspect as a result of peer pressure. Moreover, global transparency was further enhanced as information technology helped communicate the same relevant local knowledge across the firm. This was possible because internal transparency was strong, and the management control structures were designed anew to leverage the capabilities of information technology. Management controls evolve and change in form and intensity over time, particularly under the influence of changing market conditions. To understand how management controls change dynamically, a more dynamic set of management controls is proposed. “Redirecting control” plays the role of persuading individuals to turn away from old practices and adopt new ways to perform and complete tasks. “Reinforcing control” plays the role of encouraging individuals to continue to stay on the new path following redirection with increased commitment. Both redirecting and reinforcing controls can play positive and negative roles for individuals. Interchanging between these two control approaches allows senior management to persuade their subordinates to behave according to the needs and plans of the firm in successive stages of change. Management controls are perceived as positive when individuals experience support for what they perceive to be their work identities; if not, they are perceived as negative. Addressing how controls are presented to individuals may help improve their perceptions and attainment of the work identities they understand and aspire to.

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  • Stepmothers’ perceptions and experiences of stepmothers stereotypes

    Miller, Anna (2015)

    Doctoral thesis
    The University of Auckland Library

    Despite the increasing number of stepfamilies, research suggests that negative stepmother stereotypes continue to exist in contemporary society. This qualitative study aimed to explore stepmothers’ perceptions and experiences of stepmother stereotypes, and to investigate the impact, if any, that these negative representations have on women’s experiences of stepmotherhood. One hundred and thirty-eight stepmothers, living in New Zealand with their stepchild (at least some of the time), completed an anonymous online questionnaire about their perceptions and experiences of stepmother stereotypes. The average age of the participants was 36.9 years and the average period of stepmotherhood was 5.5 years. The questionnaire elicited participants' observations of positive and negative stepmother representations in a range of sources. Participants were also asked about their use of the stepmother term, and responded to four open-ended qualitative questions, which related to their experiences of the ‘wicked stepmother’ stereotype and positive aspects of the stepmother role. Participants also rated on a four-point Likert scale the extent to which they thought wicked stepmother stereotypes impacted on their experience as a stepmother. Thematic analysis was conducted on the qualitative data collected, and overall, stepmothers perceived more negative stepmother stereotypes than positive. The majority of stepmothers reported experiences of feeling, or being treated to varying degrees as if they were ‘wicked’, which were brought together in the themes ‘Boundary setting makes me feel bad’, ‘I am unmotherly’, and ‘I don’t count’. Positive experiences of being a stepmother and a repertoire of personal strategies helped to ameliorate the impact of the wicked stepmother stereotypes. Some stepmothers, however, appeared to have internalised the negative representations which led to secondary emotions of guilt, shame, self-doubt, frustration, and a sense of being ‘bad’. Overall, stepmothers rated stepmother stereotypes as having moderate impact on their experience as a stepmother, and the themes were heavily influenced by cultural expectations of motherhood. These findings are discussed in terms of existing knowledge about stepmothers, expectations of mothers, gender issues, and stereotyped identities. This study contributes to the existing body of stepfamily research, and provides discussion on the implications for clinical practice and future research directions.

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  • Caenorhabditis elegans Models to Study the Molecular Mechanisms of Alzheimer’s Disease

    Ly, Kien (2014)

    Doctoral thesis
    The University of Auckland Library

    Alzheimer’s disease (AD) is a progressive neurodegenerative disorder and is the most common form of dementia which currently affects over 40 million people worldwide. Pathologically, AD is characterized by two important hallmarks: extracellular amyloid plaques and intracellular neurofibrillary tangles, made up predominantly by proteins known as β-amyloid (Aβ) and hyperphosphorylated Tau, respectively. Mutations in the Aβ precursor protein (APP) and two proteins involved in Aβ production (presenilin 1 and 2, components of the γ-secretase complex) cause heritable early onset AD, typically prior to 65 years old. However, the majority of AD cases occur in people over the age of 65 due to multifactorial causes. Despite over two decades of intensive research, the physiological roles and mechanistic contribution of APP and Aβ to late onset AD still remain elusive. Caenorhabditis elegans is emerging as a powerful tool in the research of neurodegenerative disorders, complementing the traditional mammalian systems with straight forward genetics, simplicity of their neuronal network, and short generation time. Previous studies have shown that transgenic C. elegans overexpressing human Aβ in muscle cells develop intracellular Aβ aggregation and a progressive paralysis, while those expressing Aβ in neurons reveal behavioural deficits. To further understand Aβ, APP and to model AD related physiology as closely as possible, transgenic C. elegans strains which express full-length human APP and human β-secretase, an enzyme responsible for the first step of Aβ production, were made. The transgenes were driven by appropriate promoters and fluorescent tagged fusion proteins expressing lines were also developed. The transgenic animals displayed phenotypical changes, associated with the presence of the transgenes.

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  • Adaptive Load Shedding Developments for Smart Grid Network

    Mollah, Kaiumuzzaman (2015)

    Doctoral thesis
    The University of Auckland Library

    Electrical power systems are undergoing innovative transformation of their existing practices to realize the smart grid (SG) vision. SGs are digitally empowered electrical grids that have the capability of controlling a large number of geographically spread generation, storage and loads across transmission and distribution networks. However, currently in operation and planning of networks, the interaction between increasing distributed generation (DG) and demand response (DR) present in the system is not explicitly factored. The development and installation of smart technologies such as intelligent electronic devices (IEDs) are increasingly happening in recent years. To protect and control this highly multi-layered system the SG needs to develop and establish robust protection and control schemes. Load shedding (LS) is one of the last actions that are automatically initiated, based on its designed operation, to prevent wide area system collapse when all other possibilities have been exhausted. Most of the existing LS schemes are well established at a transmission/sub-transmission level and executed by controlling the feeder load rather than individual loads downstream. In recent years traditional networks are shifting towards a smart grid framework where devices are equipped with emerging technologies and comply with standard based sub–station communication framework, such as International Electrotechnical Commission (IEC) 61850 Generic Object Oriented Substation Event (GOOSE) messaging. Operational control elements are also shifting from distribution to the individual interconnection level. These technological developments can potentially lead to the creation of a dynamic market for Automatic LS in the foreseeable future. Several catastrophic global blackouts have occurred, including New Zealand (NZ), in the last few years. Inefficient design of existing LS schemes is one of the critical reasons at times for resulting in larger blackout footprint. In the context of SG, emergency controls (including the LS) that are used to prevent blackouts need to be revisited. It is difficult to prevent system blackouts entirely. However, protection and control procedures can be improved by using the emerging technologies to help reduce the geographical span of blackouts. In the context of emerging technologies and sub-station communication standard based framework, this research aims to systematically propose developments of improved and newer LS strategies. In this thesis the major technical issues are addressed to improve LS mechanisms and the aim is to facilitate SG adoption in realize these techniques in practice. Existing LS schemes are first investigated to address the merits of each technique. Subsequently, a number of modifications for enhancing the existing LS techniques of each method have been outlined. This thesis introduces some new techniques which help to improve overall protection and control mechanisms. The proposed systems incorporate some important power system stability elements, especially voltage and frequency, by providing a real-time and optimal load control and shedding strategy, during a situation where the power system would otherwise have become unstable. The development of algorithms and procedures based on real-time distributed intelligence across the power system network, rather than the traditional centralised scheme, will be one major contribution of this thesis. These algorithms are intended to provide a flexible and decentralised method of mitigation. A secure implementation pathway also falls under the scope of this work which is approached using emerging substation standards like IEC 61850 and other open standards and implementation pathways. Thus, this thesis demonstrates that through SG technologies there are opportunities for improving upon traditional centralised LS schemes towards a more decentralised, smarter and graceful outage implementation. Overall, the developed algorithms, models and methodologies are tested for both transmission and distribution networks. To demonstrate LS technique in an SG framework, an experimental setup at the University of Auckland power systems laboratory, is also reported. To validate the proposed LS method, real New Zealand network data has been used for all the illustrative case studies. Keywords: Automatic Under Frequency Load Shedding; Automatic Under Voltage Load Shedding, Blackout, Distribution Network, Distributed Generation, Demand Side Management, Demand Response, Distribution System, Distribution Network, Energy Shedding, Emerging Technology, Intelligent Electronic Device, GOOSE Messaging, IEC 61850, Load Shedding, Load Reduction, Load Model, Load Characteristics Programmable Logic Controller, Power Generation, Power System Protection Relaying, Power System Faults, Power System Protection, Power System Stability, Rate of Change of Frequency; Smart Grid, Transmission System, Spinning Reserve, Under Frequency, Under Voltage.

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  • The Lorenz System Near the Loss of the Foliation Condition

    Creaser, Jennifer (2015)

    Doctoral thesis
    The University of Auckland Library

    The well-known three-dimensional Lorenz system is classically studied via its reduction to the one-dimensional Lorenz map, which captures the full behaviour of the dynamics of the system. The reduction requires the existence of a stable foliation. We study a parameter regime where this so-called foliation condition fails for the rst time and, consequently, the Lorenz map no longer accurately represents the dynamics of the full system. To this end, we study how the three-dimensional phase space of the Lorenz system is organised by the global invariant manifolds of saddle equilibria and saddle periodic orbits. Speci cally, we explain and de ne two phenomena, observed by Sparrow in the 1980's. First, the so-called `half-swing' of the one-dimensional stable manifolds Ws(p ) of the secondary equilibria p from one side to the other. Secondly, the development of hooks in the Poincar e return map that marks the loss of the foliation condition. To investigate both these phenomena, we make extensive use of the continuation of orbit segments formulated by two-point boundary value problems. To explain the `half-swing' we characterise geometrically a bifurcation in the -limit of Ws(p ), which we call an - ip. We accurately compute the parameter value at which this rst - ip occurs and nd many subsequent - ips. In two parameters, we show that each - ip ends at a different codimension-two bifurcation point, called a T-point, many of which have not been found before. In particular, we discuss the - ip in the context of the known bifurcation structure around the rst T-point. To study the foliation condition we calculate the intersection curves of the two-dimensional unstable manifold Wu( ) of a periodic orbit with the classic Poincar e section. We identify when hooks form in the Poincar e map as a point of tangency of Wu( ) with the stable foliation. Subsequent continuations show that this point lies on a curve through the rst T-point in two-parameter space, which provides a connection with the - ip. Our approach allows us to identify in a convenient way the region of existence of the classic Lorenz attractor in two- and three-parameter space.

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  • Instability and transition in unsteady rotating flows

    Calabretto, Sophie (2015)

    Doctoral thesis
    The University of Auckland Library

    The unsteady flow of rotating fluids can exhibit some fascinating and elegant phenomena. The movement of fluid due to the rotation of an encompassing container, or the flow of fluid due to the rotation of a solid object immersed within a body of fluid, is of particular interest. Specifically, we focus on the dynamics resulting from an impulsive change in the rotation rate for both these internal and external flows, including the formation of boundary layers and their subsequent evolution, and the formation of instabilities. Using a combination of analytical, computational and experimental methods, we consider the flow induced by both a torus and a sphere, contained in an otherwise quiescent body of fluid, suddenly imparted with angular momentum. Our results agree well with previous work on this classical problem, known to exhibit a boundary-layer collision process, and we are able to take this problem further to consider the post-collision dynamics, encountering some new and exciting results, such as the development and propagation of a toroidal vortex pair, as a result of the boundary-layer collision, and instability of the radial jet. We also consider the flow within fluid-filled annular and toroidal containers, when there is a sudden change in the rotation rate of the container. Using both analytical and computational approaches, we explore the initial development of the impulsively generated axisymmetric boundary layer, its subsequent instability, and the larger scale transient features within this class of flows. This allows us to compare with and, perhaps, proffer an explanation for previously unexplained experimental results for the flow within a fluid-filled torus. In particular, we demonstrate that small imperfections in the torus surface, introduced during manufacture, can generate substantial secondary motion, considerably different from that which would arise if caused by centrifugal instabilities. This serves to highlight the often overlooked impact of small disturbances on the global dynamics of such flows.

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  • The Individual Characteristics of Board Members and Reported Internal Control Weakness: Evidence from China

    Lu, Yu (2015)

    Doctoral thesis
    The University of Auckland Library

    This study examines the relationship between individual characteristics of board members and internal control weaknesses using data from Chinese listed firms from 2007 to 2013. China’s first internal control regulation (2008) (“China SOX”) stipulates that the board of directors takes the main responsibility for the establishment and implementation of internal control, an approach which is different from US SOX. I examine whether or not individual characteristics of board members are related to internal control weaknesses and, if so, how does this happen. I address this issue by examining the influences of education, training, experience, certification and integrity of board members on specific internal control weaknesses and weakness remediation. In particular, given the vital role of the board chairman in Chinese internal control, I also study the association between individual characteristics of the board chairmen and internal control weaknesses. In addition, I expect that the nature of dominant shareholders (state-owned or non-state owned) and the board behaviour (independence and diligence) have an influence on the correlation between the board and internal control. I use a sample of firms with internal control problems and, based on size, industry and ownership, match these firms to a sample of control firms without internal control problems. I also conduct a series of additional tests. Results indicate that individual characteristics of board members including education, experience, certification and integrity, are related to internal control deficiencies. However, relevant training has no relationship with internal control. Results also show that individual characteristics of board chairmen are related to internal control problems. The overall results demonstrate that internal control quality is better, internal control weaknesses are reduced and weakness remediation is more likely to be applied in firms in which board members and board chairpersons have stronger qualifications. However, board behaviour and ownership nature do not influence the relationship between board members and internal control. Thus, it is suggested, board characteristics and internal control are directly linked. My findings prove reliable throughout several sensitivity examinations. It is useful for directors to know that some characteristics (education, experience, certification and integrity) of board members do make a difference.

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  • The Purpose of the Absurd in Contemporary and Recent Fine Art Practices

    Crookes, Matthew (2014)

    Doctoral thesis
    The University of Auckland Library

    My research has investigated and attempted to identify the absurd as a function within the making of Fine Art. By ‘absurd’, I am referring to a subjective state of being, centred on the individual, which allows for logical inconsistency and contradiction. This absurd was initially identified by the Danish philosopher Soren Kierkegaard, in reaction to the systemic and objective philosophies of Hegel, Kant and others; and which in turn was elaborated upon by later writers such as Albert Camus and Maurice MerleauPonty. It is often associated with, but discrete from, Existential philosophy. I have examined how this interpretation of the absurd plays out in the practices of various recent and contemporary artists, including Francis Alys, Bas Jan Ader, Martin Creed, Simon Starling and John Latham. I have described how the Absurd is a necessary part in enabling certain kinds of contemporary Fine Art practice, notably in the way that the detachment from a universal logic permits an inner rationale to emerge in an artist’s praxis. Throughout my research I have made works which in which I endeavour to accentuate and demonstrate the Absurd function within the Art work. I have done so by focussing in my practice on activities whose ‘purpose’ is internalised and/or secondary; journeys or activities which are out of proportion to the purpose attributed to them.

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