Validation Gating for Non-Linear Non-Gaussian Target Tracking

This paper develops a general theory of validation gating for non-linear non-Gaussian mod- els. Validation gates are used in target tracking to cull very unlikely measurement-to-track associa- tions, before remaining association ambiguities are handled by a more comprehensive (and expensive) data association scheme. The essential property of a gate is to accept a high percentage of correct associ- ations, thus maximising track accuracy, but provide a su±ciently tight bound to minimise the number of ambiguous associations. For linear Gaussian systems, the ellipsoidal vali- dation gate is standard, and possesses the statistical property whereby a given threshold will accept a cer- tain percentage of true associations. This property does not hold for non-linear non-Gaussian models. As a system departs from linear-Gaussian, the ellip- soid gate tends to reject a higher than expected pro- portion of correct associations and permit an excess of false ones. In this paper, the concept of the ellip- soidal gate is extended to permit correct statistics for the non-linear non-Gaussian case. The new gate is demonstrated by a bearing-only tracking example.

Asset life prediction and maintenance decision-making using a non-linear non-Gaussian state space model

Estimating and predicting degradation processes of engineering assets is crucial for reducing the cost and insuring the productivity of enterprises. Assisted by modern condition monitoring (CM) technologies, most asset degradation processes can be revealed by various degradation indicators extracted from CM data. Maintenance strategies developed using these degradation indicators (i.e. condition-based maintenance) are more cost-effective, because unnecessary maintenance activities are avoided when an asset is still in a decent health state. A practical difficulty in condition-based maintenance (CBM) is that degradation indicators extracted from CM data can only partially reveal asset health states in most situations. Underestimating this uncertainty in relationships between degradation indicators and health states can cause excessive false alarms or failures without pre-alarms. The state space model provides an efficient approach to describe a degradation process using these indicators that can only partially reveal health states. However, existing state space models that describe asset degradation processes largely depend on assumptions such as, discrete time, discrete state, linearity, and Gaussianity. The discrete time assumption requires that failures and inspections only happen at fixed intervals. The discrete state assumption entails discretising continuous degradation indicators, which requires expert knowledge and often introduces additional errors. The linear and Gaussian assumptions are not consistent with nonlinear and irreversible degradation processes in most engineering assets. This research proposes a Gamma-based state space model that does not have discrete time, discrete state, linear and Gaussian assumptions to model partially observable degradation processes. Monte Carlo-based algorithms are developed to estimate model parameters and asset remaining useful lives. In addition, this research also develops a continuous state partially observable semi-Markov decision process (POSMDP) to model a degradation process that follows the Gamma-based state space model and is under various maintenance strategies. Optimal maintenance strategies are obtained by solving the POSMDP. Simulation studies through the MATLAB are performed; case studies using the data from an accelerated life test of a gearbox and a liquefied natural gas industry are also conducted. The results show that the proposed Monte Carlo-based EM algorithm can estimate model parameters accurately. The results also show that the proposed Gamma-based state space model have better fitness result than linear and Gaussian state space models when used to process monotonically increasing degradation data in the accelerated life test of a gear box. Furthermore, both simulation studies and case studies show that the prediction algorithm based on the Gamma-based state space model can identify the mean value and confidence interval of asset remaining useful lives accurately. In addition, the simulation study shows that the proposed maintenance strategy optimisation method based on the POSMDP is more flexible than that assumes a predetermined strategy structure and uses the renewal theory. Moreover, the simulation study also shows that the proposed maintenance optimisation method can obtain more cost-effective strategies than a recently published maintenance strategy optimisation method by optimising the next maintenance activity and the waiting time till the next maintenance activity simultaneously.

Non-invasive assessment of tear film surface quality

The tear film plays an important role preserving the health of the ocular surface and maintaining the optimal refractive power of the cornea. Moreover dry eye syndrome is one of the most commonly reported eye health problems. This syndrome is caused by abnormalities in the properties of the tear film. Current clinical tools to assess the tear film properties have shown certain limitations. The traditional invasive methods for the assessment of tear film quality, which are used by most clinicians, have been criticized for the lack of reliability and/or repeatability. A range of non-invasive methods of tear assessment have been investigated, but also present limitations. Hence no “gold standard” test is currently available to assess the tear film integrity. Therefore, improving techniques for the assessment of the tear film quality is of clinical significance and the main motivation for the work described in this thesis. In this study the tear film surface quality (TFSQ) changes were investigated by means of high-speed videokeratoscopy (HSV). In this technique, a set of concentric rings formed in an illuminated cone or a bowl is projected on the anterior cornea and their reflection from the ocular surface imaged on a charge-coupled device (CCD). The reflection of the light is produced in the outer most layer of the cornea, the tear film. Hence, when the tear film is smooth the reflected image presents a well structure pattern. In contrast, when the tear film surface presents irregularities, the pattern also becomes irregular due to the light scatter and deviation of the reflected light. The videokeratoscope provides an estimate of the corneal topography associated with each Placido disk image. Topographical estimates, which have been used in the past to quantify tear film changes, may not always be suitable for the evaluation of all the dynamic phases of the tear film. However the Placido disk image itself, which contains the reflected pattern, may be more appropriate to assess the tear film dynamics. A set of novel routines have been purposely developed to quantify the changes of the reflected pattern and to extract a time series estimate of the TFSQ from the video recording. The routine extracts from each frame of the video recording a maximized area of analysis. In this area a metric of the TFSQ is calculated. Initially two metrics based on the Gabor filter and Gaussian gradient-based techniques, were used to quantify the consistency of the pattern’s local orientation as a metric of TFSQ. These metrics have helped to demonstrate the applicability of HSV to assess the tear film, and the influence of contact lens wear on TFSQ. The results suggest that the dynamic-area analysis method of HSV was able to distinguish and quantify the subtle, but systematic degradation of tear film surface quality in the inter-blink interval in contact lens wear. It was also able to clearly show a difference between bare eye and contact lens wearing conditions. Thus, the HSV method appears to be a useful technique for quantitatively investigating the effects of contact lens wear on the TFSQ. Subsequently a larger clinical study was conducted to perform a comparison between HSV and two other non-invasive techniques, lateral shearing interferometry (LSI) and dynamic wavefront sensing (DWS). Of these non-invasive techniques, the HSV appeared to be the most precise method for measuring TFSQ, by virtue of its lower coefficient of variation. While the LSI appears to be the most sensitive method for analyzing the tear build-up time (TBUT). The capability of each of the non-invasive methods to discriminate dry eye from normal subjects was also investigated. The receiver operating characteristic (ROC) curves were calculated to assess the ability of each method to predict dry eye syndrome. The LSI technique gave the best results under both natural blinking conditions and in suppressed blinking conditions, which was closely followed by HSV. The DWS did not perform as well as LSI or HSV. The main limitation of the HSV technique, which was identified during the former clinical study, was the lack of the sensitivity to quantify the build-up/formation phase of the tear film cycle. For that reason an extra metric based on image transformation and block processing was proposed. In this metric, the area of analysis was transformed from Cartesian to Polar coordinates, converting the concentric circles pattern into a quasi-straight lines image in which a block statistics value was extracted. This metric has shown better sensitivity under low pattern disturbance as well as has improved the performance of the ROC curves. Additionally a theoretical study, based on ray-tracing techniques and topographical models of the tear film, was proposed to fully comprehend the HSV measurement and the instrument’s potential limitations. Of special interested was the assessment of the instrument’s sensitivity under subtle topographic changes. The theoretical simulations have helped to provide some understanding on the tear film dynamics, for instance the model extracted for the build-up phase has helped to provide some insight into the dynamics during this initial phase. Finally some aspects of the mathematical modeling of TFSQ time series have been reported in this thesis. Over the years, different functions have been used to model the time series as well as to extract the key clinical parameters (i.e., timing). Unfortunately those techniques to model the tear film time series do not simultaneously consider the underlying physiological mechanism and the parameter extraction methods. A set of guidelines are proposed to meet both criteria. Special attention was given to a commonly used fit, the polynomial function, and considerations to select the appropriate model order to ensure the true derivative of the signal is accurately represented. The work described in this thesis has shown the potential of using high-speed videokeratoscopy to assess tear film surface quality. A set of novel image and signal processing techniques have been proposed to quantify different aspects of the tear film assessment, analysis and modeling. The dynamic-area HSV has shown good performance in a broad range of conditions (i.e., contact lens, normal and dry eye subjects). As a result, this technique could be a useful clinical tool to assess tear film surface quality in the future.

Evolutionary biology of Gondwanan non-biting midges (Diptera: Chironomidae)

The potential restriction to effective dispersal and gene flow caused by habitat fragmentation can apply to multiple levels of evolutionary scale; from the fragmentation of ancient supercontinents driving diversification and speciation on disjunct landmasses, to the isolation of proximate populations as a result of their inability to cross intervening unsuitable habitat. Investigating the role of habitat fragmentation in driving diversity within and among taxa can thus include inferences of phylogenetic relationships among taxa, assessments of intraspecific phylogeographic structure and analyses of gene flow among neighbouring populations. The proposed Gondwanan clade within the chironomid (non-biting midge) subfamily Orthocladiinae (Diptera: Chironomidae) represents a model system for investigating the role that population fragmentation and isolation has played at different evolutionary scales. A pilot study by Krosch et al (2009) indentified several highly divergent lineages restricted to ancient rainforest refugia and limited gene flow among proximate sites within a refuge for one member of this clade, Echinocladius martini Cranston. This study provided a framework for investigating the evolutionary history of this taxon and its relatives more thoroughly. Populations of E. martini were sampled in the Paluma bioregion of northeast Queensland to investigate patterns of fine-scale within- and among-stream dispersal and gene flow within a refuge more rigorously. Data was incorporated from Krosch et al (2009) and additional sites were sampled up- and downstream of the original sites. Analyses of genetic structure revealed strong natal site fidelity and high genetic structure among geographically proximate streams. Little evidence was found for regular headwater exchange among upstream sites, but there was distinct evidence for rare adult flight among sites on separate stream reaches. Overall, however, the distribution of shared haplotypes implied that both larval and adult dispersal was largely limited to the natal stream channel. Patterns of regional phylogeographic structure were examined in two related austral orthoclad taxa – Naonella forsythi Boothroyd from New Zealand and Ferringtonia patagonica Sæther and Andersen from southern South America – to provide a comparison with patterns revealed in their close relative E. martini. Both taxa inhabit tectonically active areas of the southern hemisphere that have also experienced several glaciation events throughout the Plio-Pleistocene that are thought to have affected population structure dramatically in many taxa. Four highly divergent lineages estimated to have diverged since the late Miocene were revealed in each taxon, mirroring patterns in E. martini; however, there was no evidence for local geographical endemism, implying substantial range expansion post-diversification. The differences in pattern evident among the three related taxa were suggested to have been influenced by variation in the responses of closed forest habitat to climatic fluctuations during interglacial periods across the three landmasses. Phylogeographic structure in E. martini was resolved at a continental scale by expanding upon the sampling design of Krosch et al (2009) to encompass populations in southeast Queensland, New South Wales and Victoria. Patterns of phylogeographic structure were consistent with expectations and several previously unrecognised lineages were revealed from central- and southern Australia that were geographically endemic to closed forest refugia. Estimated divergence times were congruent with the timing of Plio-Pleistocene rainforest contractions across the east coast of Australia. This suggested that dispersal and gene flow of E. martini among isolated refugia was highly restricted and that this taxon was susceptible to the impacts of habitat change. Broader phylogenetic relationships among taxa considered to be members of this Gondwanan orthoclad group were resolved in order to test expected patterns of evolutionary affinities across the austral continents. The inferred phylogeny and estimated divergence times did not accord with expected patterns based on the geological sequence of break-up of the Gondwanan supercontinent and implied instead several transoceanic dispersal events post-vicariance. Difficulties in appropriate taxonomic sampling and accurate calibration of molecular phylogenies notwithstanding, the sampling regime implemented in the current study has been the most intensive yet performed for austral members of the Orthocladiinae and unsurprisingly has revealed both novel taxa and phylogenetic relationships within and among described genera. Several novel associations between life stages are made here for both described and previously unknown taxa. Investigating evolutionary relationships within and among members of this clade of proposed Gondwanan orthoclad taxa has demonstrated that a complex interaction between historical population fragmentation and dispersal at several levels of evolutionary scale has been important in driving diversification in this group. While interruptions to migration, colonisation and gene flow driven by population fragmentation have clearly contributed to the development and maintenance of much of the diversity present in this group, long-distance dispersal has also played a role in influencing diversification of continental biotas and facilitating gene flow among disjunct populations.

Optical non-destructive evaluation of articular cartilage integrity : a review

This paper reviews the current status of the application of optical non-destructive methods, particularly infrared (IR) and near infrared (NIR), in the evaluation of the physiological integrity of articular cartilage. It is concluded that a significant amount of work is still required in order to achieve specificity and clinical applicability of these methods in the assessment and treatment of dysfunctional articular joints.

Sustainable assessment for large science classes : non-multiple choice, randomised assignments through a Learning Management System

This paper reports on the development of a tool that generates randomised, non-multiple choice assessment within the BlackBoard Learning Management System interface. An accepted weakness of multiple-choice assessment is that it cannot elicit learning outcomes from upper levels of Biggs’ SOLO taxonomy. However, written assessment items require extensive resources for marking, and are susceptible to copying as well as marking inconsistencies for large classes. This project developed an assessment tool which is valid, reliable and sustainable and that addresses the issues identified above. The tool provides each student with an assignment assessing the same learning outcomes, but containing different questions, with responses in the form of words or numbers. Practice questions are available, enabling students to obtain feedback on their approach before submitting their assignment. Thus, the tool incorporates automatic marking (essential for large classes), randomised tasks to each student (reducing copying), the capacity to give credit for working (feedback on the application of theory), and the capacity to target higher order learning outcomes by requiring students to derive their answers rather than choosing them. Results and feedback from students are presented, along with technical implementation details.

Equity in the twenty-first century

Issues of equity and inequity have always been part of employment relations and are a fundamental part of the industrial landscape. For example, in most countries in the nineteenth century and a large part of the twentieth century women and members of ethnic groups (often a minority in the workforce) were barred from certain occupations, industries or work locations, and received less pay than the dominant male ethnic group for the same work. In recent decades attention has been focused on issues of equity between groups, predominantly women and different ethnic groups in the workforce. This has been embodied in industrial legislation, for example in equal pay for women and men, and frequently in specific equity legislation. In this way a whole new area of law and associated workplace practice has developed in many countries. Historically, employment relations and industrial relations research has not examined employment issues disaggregated by gender or ethnic group. Born out of concern with conflict and regulation at the workplace, studies tended to concentrate on white, male, unionized workers in manufacturing and heavy industry (Ackers, 2002, p. 4). The influential systems model crafted by Dunlop (1958) gave rise to The discipline’s preoccupation with the ‘problem of order’ [which] ensures the invisibility of women, not only because women have generally been less successful in mobilizing around their own needs and discontents, but more profoundly because this approach identifies the employment relationship as the ultimate source of power and conflict at work (Forrest, 1993, p. 410). While ‘the system approach does not deliberately exclude gender . . . by reproducing a very narrow research approach and understanding of issues of relevance for the research, gender is in general excluded or looked on as something of peripheral interest’ (Hansen, 2002, p. 198). However, long-lived patterns of gender segregation in occupations and industries, together with discriminatory access to work and social views about women and ethnic groups in the paid workforce, mean that the employment experience of women and ethnic groups is frequently quite different to that of men in the dominant ethnic group. Since the 1980s, research into women and employment has figured in the employment relations literature, but it is often relegated to a separate category in specific articles or book chapters, with women implicitly or explicitly seen as the atypical or exceptional worker (Hansen, 2002; Wajcman, 2000). The same conclusion can be reached for other groups with different labour force patterns and employment outcomes. This chapter proposes that awareness of equity issues is central to employment relations. Like industrial relations legislation and approaches, each country will have a unique set of equity policies and legislation, reflecting their history and culture. Yet while most books on employment and industrial relations deal with issues of equity in a separate chapter (most commonly on equity for women or more recently on ‘diversity’), the reality in the workplace is that all types of legislation and policies which impact on the wages and working conditions interact, and their impact cannot be disentangled one from another. When discussing equity in workplaces in the twenty-first century we are now faced with a plethora of different terms in English. Terms used include discrimination, equity, equal opportunity, affirmative action and diversity with all its variants (workplace diversity, managing diversity, and so on). There is a lack of agreed definitions, particularly when the terms are used outside of a legislative context. This ‘shifting linguistic terrain’ (Kennedy-Dubourdieu, 2006b, p. 3) varies from country to country and changes over time even within the one country. There is frequently a division made between equity and its related concepts and the range of expressions using the term ‘diversity’ (Wilson and Iles, 1999; Thomas and Ely, 1996). These present dilemmas for practitioners and researchers due to the amount and range of ideas prevalent – and the breadth of issues that are covered when we say ‘equity and diversity in employment’. To add to these dilemmas, the literature on equity and diversity has become bifurcated: the literature on workplace diversity/management diversity appears largely in the business literature while that on equity in employment appears frequently in legal and industrial relations journals. Workplaces of the twenty-first century differ from those of the nineteenth and twentieth century not only in the way they deal with individual and group differences but also in the way they interpret what are fair and equitable outcomes for different individuals and groups. These variations are the result of a range of social conditions, legislation and workplace constraints that have influenced the development of employment equity and the management of diversity. Attempts to achieve employment equity have primarily been dealt with through legislative means, and in the last fifty years this legislation has included elements of anti-discrimination, affirmative action, and equal employment opportunity in virtually all OECD countries (Mor Barak, 2005, pp. 17–52). Established on human rights and social justice principles, this legislation is based on the premise that systemic discrimination has and/or continues to exist in the labour force and particular groups of citizens have less advantageous employment outcomes. It is based on group identity, and employment equity programmes in general apply across all workplaces and are mandatory. The more recent notions of diversity in the workplace are based on ideas coming principally from the USA in the 1980s which have spread widely in the Western world since the 1990s. Broadly speaking, diversity ideas focus on individual differences either on their own or in concert with the idea of group differences. The diversity literature is based on a business case: that is diversity is profitable in a variety of ways for business, and generally lacks a social justice or human rights justification (Burgess et al., 2009, pp. 81–2). Managing diversity is represented at the organizational level as a voluntary and local programme. This chapter discusses some major models and theories for equity and diversity. It begins by charting the history of ideas about equity in employment and then briefly discusses what is meant by equality and equity. The chapter then analyses the major debates about the ways in which equity can be achieved. The more recent ideas about diversity are then discussed, including the history of these ideas and the principles which guide this concept. The following section discusses both major frameworks of equity and diversity. The chapter then raises some ways in which insights from the equity and diversity literature can inform employment relations. Finally, the future of equity and diversity ideas is discussed.

Focusing on patients : differences between the practice of expert and non-expert nephrology nurses

Specialisation in nursing enables a nurse to focus, in much greater depth, on the requisite knowledge and skills for providing patients with the best possible care. Nephrology nursing is one such area where specialisation has evolved. The characteristic focus of practice emerged as an important feature during a study into the process of expertise acquisition in nephrology nursing practice. Using grounded theory methodology, this study involved 6 non-expert and 11 expert nurses and took place in one renal unit in New South Wales. Nephrology nursing practice was observed for 103 hours, and this was immediately followed by semi-structured interviews. The characteristic of focus was conceptualised as the nurses' centre of attention or concentration while they were undertaking nursing activities. Focus ranged from inexperienced non-expert nurses concentrating predominantly on the immediate task at hand, experienced non-expert nurses who focussed on the medium term to expert nurses who viewed actions (and their possible consequences) more broadly and in the longer term. Of significance to nursing, is how nephrology nurses alter their focus of practice as they acquire and exercise their developing expertise in this specialty.