A hidden Markov model and relative entropy rate approach to vision-based dim target detection for UAV sense-and-avoid

Uninhabited aerial vehicles (UAVs) are a cutting-edge technology that is at the forefront of aviation/aerospace research and development worldwide. Many consider their current military and defence applications as just a token of their enormous potential. Unlocking and fully exploiting this potential will see UAVs in a multitude of civilian applications and routinely operating alongside piloted aircraft. The key to realising the full potential of UAVs lies in addressing a host of regulatory, public relation, and technological challenges never encountered be- fore. Aircraft collision avoidance is considered to be one of the most important issues to be addressed, given its safety critical nature. The collision avoidance problem can be roughly organised into three areas: 1) Sense; 2) Detect; and 3) Avoid. Sensing is concerned with obtaining accurate and reliable information about other aircraft in the air; detection involves identifying potential collision threats based on available information; avoidance deals with the formulation and execution of appropriate manoeuvres to maintain safe separation. This thesis tackles the detection aspect of collision avoidance, via the development of a target detection algorithm that is capable of real-time operation onboard a UAV platform. One of the key challenges of the detection problem is the need to provide early warning. This translates to detecting potential threats whilst they are still far away, when their presence is likely to be obscured and hidden by noise. Another important consideration is the choice of sensors to capture target information, which has implications for the design and practical implementation of the detection algorithm. The main contributions of the thesis are: 1) the proposal of a dim target detection algorithm combining image morphology and hidden Markov model (HMM) filtering approaches; 2) the novel use of relative entropy rate (RER) concepts for HMM filter design; 3) the characterisation of algorithm detection performance based on simulated data as well as real in-flight target image data; and 4) the demonstration of the proposed algorithm's capacity for real-time target detection. We also consider the extension of HMM filtering techniques and the application of RER concepts for target heading angle estimation. In this thesis we propose a computer-vision based detection solution, due to the commercial-off-the-shelf (COTS) availability of camera hardware and the hardware's relatively low cost, power, and size requirements. The proposed target detection algorithm adopts a two-stage processing paradigm that begins with an image enhancement pre-processing stage followed by a track-before-detect (TBD) temporal processing stage that has been shown to be effective in dim target detection. We compare the performance of two candidate morphological filters for the image pre-processing stage, and propose a multiple hidden Markov model (MHMM) filter for the TBD temporal processing stage. The role of the morphological pre-processing stage is to exploit the spatial features of potential collision threats, while the MHMM filter serves to exploit the temporal characteristics or dynamics. The problem of optimising our proposed MHMM filter has been examined in detail. Our investigation has produced a novel design process for the MHMM filter that exploits information theory and entropy related concepts. The filter design process is posed as a mini-max optimisation problem based on a joint RER cost criterion. We provide proof that this joint RER cost criterion provides a bound on the conditional mean estimate (CME) performance of our MHMM filter, and this in turn establishes a strong theoretical basis connecting our filter design process to filter performance. Through this connection we can intelligently compare and optimise candidate filter models at the design stage, rather than having to resort to time consuming Monte Carlo simulations to gauge the relative performance of candidate designs. Moreover, the underlying entropy concepts are not constrained to any particular model type. This suggests that the RER concepts established here may be generalised to provide a useful design criterion for multiple model filtering approaches outside the class of HMM filters. In this thesis we also evaluate the performance of our proposed target detection algorithm under realistic operation conditions, and give consideration to the practical deployment of the detection algorithm onboard a UAV platform. Two fixed-wing UAVs were engaged to recreate various collision-course scenarios to capture highly realistic vision (from an onboard camera perspective) of the moments leading up to a collision. Based on this collected data, our proposed detection approach was able to detect targets out to distances ranging from about 400m to 900m. These distances, (with some assumptions about closing speeds and aircraft trajectories) translate to an advanced warning ahead of impact that approaches the 12.5 second response time recommended for human pilots. Furthermore, readily available graphic processing unit (GPU) based hardware is exploited for its parallel computing capabilities to demonstrate the practical feasibility of the proposed target detection algorithm. A prototype hardware-in- the-loop system has been found to be capable of achieving data processing rates sufficient for real-time operation. There is also scope for further improvement in performance through code optimisations. Overall, our proposed image-based target detection algorithm offers UAVs a cost-effective real-time target detection capability that is a step forward in ad- dressing the collision avoidance issue that is currently one of the most significant obstacles preventing widespread civilian applications of uninhabited aircraft. We also highlight that the algorithm development process has led to the discovery of a powerful multiple HMM filtering approach and a novel RER-based multiple filter design process. The utility of our multiple HMM filtering approach and RER concepts, however, extend beyond the target detection problem. This is demonstrated by our application of HMM filters and RER concepts to a heading angle estimation problem.

Industrial design in endoscopy : the development of a tissue and organ extractor

Throughout history, developments in medicine have aimed to improve patient quality of life, and reduce the trauma associated with surgical treatment. Surgical access to internal organs and bodily structures has been traditionally via large incisions. Endoscopic surgery presents a technique for surgical access via small (1 Omm) incisions by utilising a scope and camera for visualisation of the operative site. Endoscopy presents enormous benefits for patients in terms of lower post operative discomfort, and reduced recovery and hospitalisation time. Since the first gall bladder extraction operation was performed in France in 1987, endoscopic surgery has been embraced by the international medical community. With the adoption of the new technique, new problems never previously encountered in open surgery, were revealed. One such problem is that the removal of large tissue specimens and organs is restricted by the small incision size. Instruments have been developed to address this problem however none of the devices provide a totally satisfactory solution. They have a number of critical weaknesses: -The size of the access incision has to be enlarged, thereby compromising the entire endoscopic approach to surgery. - The physical quality of the specimen extracted is very poor and is not suitable to conduct the necessary post operative pathological examinations. -The safety of both the patient and the physician is jeopardised. The problem of tissue and organ extraction at endoscopy is investigated and addressed. In addition to background information covering endoscopic surgery, this thesis describes the entire approach to the design problem, and the steps taken before arriving at the final solution. This thesis contributes to the body of knowledge associated with the development of endoscopic surgical instruments. A new product capable of extracting large tissue specimens and organs in endoscopy is the final outcome of the research.

Tendering ethics : a study of collusive tendering from a marketing perspective

This thesis provides a behavioural perspective to the problem of collusive tendering in the construction market by examining the decision making factors of individuals potentially involved in such agreements using marketing ethics theory and techniques. The findings of a cross disciplinary literature review were synthesised into a model of factors theoretically expected to determine the individual's behavioural intent towards a set of collusive tendering agreements and the means of reaching them. The factors were grouped as internal cognitive (the individuals' value systems) and affective (demographic and psychographic characteristics) as well as external environmental (legal, industrial and organisational codes and norms) and situational (company, market and economic conditions). The model was tested using empirical data collected through a questionnaire survey of estimators employed in the largest Australian construction firms. All forms of explicit collusive tendering agreements were considered as having a prohibitive moral content by the majority of respondents who also clearly differentiated between agreements and discussions of contract terms (which they found to be a moral concern but not prohibitive) or of prices. The comparisons between those of the respondents that would never participate in a collusive agreement and the potential offenders clearly showed two distinctly different groups. The law abiding estimators are less reliant on situational factors, happier and more comfortable in their work environments and they live according to personal value and belief systems. The potential offenders on the other hand are mistrustful of colleagues, feel their values are not respected, put company priorities above principles and none of them is religious or a member of a professional body. The research results indicate that Australian estimators are, overall law abiding and principled and accept the existing codification of collusion as morally defensible and binding. Professional bodies' and organisational codes of conduct as well as personal value and belief systems that guide one's own conduct appear to be deterrents to collusive tendering intent and so are moral comfort and work satisfaction. These observations are potential indicators of areas where intervention and behaviour modification can increase individuals' resistance to collusion.

Dangerous places: A novel

Dangerous Places is a novel about the gap between mythological (or 'dreamed') constructions of reality and actual life. The story centres on V en, a married woman with two young children. Her love for her children is fiercely protective and encompassing, but she feels alienated from her husband and to a certain extent her society; so when her first love, Yanni, re-enters her life,she is strongly tempted to resume her affair with him. She is however seduced more by the memories she has 'mythologized' about him than by his physical reality; in the course of the novel she is forced to come to terms with her own delusions. The subplot of the novel involves other characters who are caught between illusion and reality as well, and who deal with 'truth' in differing ways. The themes of the book are explored using a number of structures which underlie and support the surface story. The Greek myths of Adonis/ Aphrodite and Hades/Persephone are framing agents for the plot, and the setting in contemporary Brisbane and North Stradbroke Island is symbolic.

Marginalising the mainstream : a signed performance of The Miracle Worker places deaf issues centre-stage

William Gibson’s The Miracle Worker was staged at the Brisbane Powerhouse June 2009 by Crossbow Productions. In this adaption, people with hearing impairment were privileged through the use of shadow-signing, unscripted signing and the appropriation of signing as a theatrical language in itself. 250 people living with hearing impairment attended the production, 70 had never attended a theatrical event before. During the post-performance discussions hearing audience members expressed feelings of displacement through experiencing the culture of the deaf society and not grasping some of the ideas. This paper argues that this inversion enhanced meaning making for all and illustrates a way forward to encourage the signing of more theatrical events.

An investigation into how the imagining of the nation is affected by understandings of the Internet

My research is located in an abiding concern with the nation and takes a special interest in the predictions and expectations surrounding the impact of the Internet on how this institution is lived. It is my hypothesis that the effects of the Internet are not limited only to those who are users but extends even to those who may never have witnessed its workings. The research question I began with: how is the imagining of the nation affected by our understandings and expectations of the Internet, developed through the writing of the first three chapters to: how is the living of the nation affected by the Internet’s inflection on lived time and lived space?

The miracle worker

Helen Keller’s fight to speak, to understand, to love aided by her teacher Annie Sullivan was nothing short of a miracle. This is her story. Crossbow Productions staged six performances of The Miracle Worker at the Brisbane Powerhouse in June 2009 to raise awareness of people living with disabilities. The play was shadow signed for the hearing impaired and tactile tours of the set were held before each performance for the vision impaired. Over 200 hearing and vision impaired attended and 70 of these had never been to the theatre before. I’m deaf and we should be able to go to anything, and you’ve done that for us. As a blind person, I got a great deal from it. I found it extremely moving. There should be a thousand or so in the audience rather than a hundred so that everyone can experience it.

Who benefits from marriage?

The phenomenon that married men earn higher average wages than unmarried men, the so-called marriage premium, is well known. However, the robustness of the marriage premium across the wage distribution and the underlying causes of the marriage premium deserve closer scrutiny. Focusing on the entire wage distribution and employing recently developed semi-nonparametric tests for quantile treatment effects, our findings cast doubt on the robustness of the premium. We find that the premium is explained by selection above the median, whereas a positive premium is obtained only at very low wages. We argue that the causal effect at low wages is probably attributable to employer discrimination.

The inadequacy of embedded markup for cultural heritage texts

Embedded generalized markup, as applied by digital humanists to the recording and studying of our textual cultural heritage, suffers from a number of serious technical drawbacks. As a result of its evolution from early printer control languages, generalized markup can only express a document’s ‘logical’ structure via a repertoire of permissible printed format structures. In addition to the well-researched overlap problem, the embedding of markup codes into texts that never had them when written leads to a number of further difficulties: the inclusion of potentially obsolescent technical and subjective information into texts that are supposed to be archivable for the long term, the manual encoding of information that could be better computed automatically, and the obscuring of the text by highly complex technical data. Many of these problems can be alleviated by asserting a separation between the versions of which many cultural heritage texts are composed, and their content. In this way the complex inter-connections between versions can be handled automatically, leaving only simple markup for individual versions to be handled by the user.

Quantification of the relationship between Fuser Roller Temperature and Laser Printer Emissions

Recently published studies not only demonstrated that laser printers are often significant sources of ultrafine particles, but they also shed light on particle formation mechanisms. While the role of fuser roller temperature as a factor affecting particle formation rate has been postulated, its impact has never been quantified. To address this gap in knowledge, this study measured emissions from 30 laser printers in chamber using a standardized printing sequence, as well as monitoring fuser roller temperature. Based on a simplified mass balance equation, the average emission rates of particle number, PM2.5 and O3 were calculated. The results showed that: almost all printers were found to be high particle number emitters (i.e. > 1.01×1010 particles/min); colour printing generated more PM2.5 than monochrome printing; and all printers generated significant amounts of O3. Particle number emissions varied significantly during printing and followed the cycle of fuser roller temperature variation, which points to temperature being the strongest factor controlling emissions. For two sub-groups of printers using the same technology (heating lamps), systematic positive correlations, in the form of a power law, were found between average particle number emission rate and average roller temperature. Other factors, such as fuser material and structure, are also thought to play a role, since no such correlation was found for the remaining two sub-groups of printers using heating lamps, or for the printers using heating strips. In addition, O3 and total PM2.5 were not found to be statistically correlated with fuser temperature.

“Entrepreneurial management” as a strategic choice in firm behavior : linking it with performance

Establishing the core principals of “entrepreneurial management” within an organization describes a certain strategic choice that affects a company in six dimensions, according to Stevenson (1983). Our aim is to empirically measure entrepreneurial management (it’s existence and degree) and to link this measured strategic choice (for or against) entrepreneurial management with firm performance. Our argument here is that companies that follow core principals of entrepreneurial management should outperform other more administrative firms in certain measures of strategic performance. This paper builds on an empirical investigation published by Brown, Davidson & Wiklund (2001), who have developed and tested a reliable measurement instrument for Stevenson’s definition of “entrepreneurial management” (Stevenson 1983, Stevenson & Jarillo 1990). In the first part of our paper we aim to replicate and to some extent improve this study. In the second part we link the measured degree of “entrepreneurial management” with firm performance. To our knowledge, even so Stevenson’s definition of entrepreneurial management is commonly acknowledged and Brown et al. (2001) developed a reliable instrument to empirically capture this behavioral approach to management, the construct of entrepreneurial management never before has been linked to firm performance in an empirical study. Since most papers on corporate entrepreneurship and firm performance are based on Covin & Slevin’s (1991) or Miller’s (1983) concept of entrepreneurial orientation, we contribute to the literature on corporate entrepreneurship in a novel way, given the fact that the entrepreneurial management dimensions measured in our study can theoretically and empirically be clearly distinguished from the construct of entrepreneurial orientation as defined by Covin & Selvin (1991).

Issues and challenges in higher education leadership : engaging for change

It is proposed from this study that engaging productively with others to achieve change has never been more critical in educational environments, such as universities. Via semi-structured interviews with a cohort of senior leaders from one Australian university, this paper explores their perceptions of the key issues and challenges facing them in their work. The study found that the most significant challenges centred around the need for strategic leadership, flexibility, creativity and change-capability; responding to competing tensions and remaining relevant; maintaining academic quality; and managing fiscal and people resources. Sound interpersonal engagement, particularly in terms of change leadership capability, was found to be critical to meeting the key challenges identified by most participants. In light of the findings from the sample studied some tentative implications for leadership and leadership development in university environments are proposed, along with suggestions for further empirical exploration.

Exploring the Pro‐Am interface between production and produsage

This conference celebrates the passing of 40 years since the establishment of the Internet (dating this, presumably, to the first connection between two nodes on ARPANET in October 1969). For a gathering of media scholars such as this, however, it may be just as important not only to mark the first testing of the core technologies upon which much of our present‐day Net continues to build, but also to reflect on another recent milestone: the 20th anniversary of what is today arguably the chief interface through which billions around the world access and experience the Internet – the World Wide Web, launched by Tim Berners‐Lee in 1989.

The probability archive : from essence to uncertainty in the growth of knowledge

From a ‘cultural science’ perspective, this paper traces one aspect of a more general shift, from the realist representational regime of modernity to the productive DIY systems of the internet era. It argues that collecting and archiving is transformed by this change. Modern museums – and also broadcast television – were based on determinist or ‘essence’ theory; while internet archives like YouTube (and the internet as an archive) are based on ‘probability’ theory. The paper goes through the differences between modernist ‘essence’ and postmodern ‘probability’; starting from the obvious difference that in a museum each object is selected by experts for its intrinsic properties, while on the internet you don’t know what you will find. The status of individual objects is uncertain, although the productivity of the overall archive is unlimited. The paper links these differences with changes in contemporary culture – from a Newtonian to a quantum universe, progress to risk, institutional structure to evolutionary change, objectivity to uncertainty, identity to performance. Borrowing some of its methodology from science fiction, the paper uses examples from museums and online archives, ranging from the oldest stone tool in the world to the latest tribute vid on the net.

Marital loss, mental health and the role of perceived social support : findings from six waves of an Australian population based panel study

Objectives: To investigate the impact of transitions out of marriage (separation, widowhood) on the self reported mental health of men and women, and examine whether perceptions of social support play an intervening role. ---------- Methods: The analysis used six waves (2001–06) of an Australian population based panel study, with an analytical sample of 3017 men and 3225 women. Mental health was measured using the MHI-5 scale scored 0–100 (α=0.97), with a higher score indicating better mental health. Perceptions of social support were measured using a 10-item scale ranging from 10 to 70 (α=0.79), with a higher score indicating higher perceived social support. A linear mixed model for longitudinal data was used, with lags for marital status, mental health and social support. ---------- Results: After adjustment for social characteristics there was a decline in mental health for men who separated (−5.79 points) or widowed (−7.63 points), compared to men who remained married. Similar declines in mental health were found for women who separated (−6.65 points) or became widowed (−9.28 points). The inclusion of perceived social support in the models suggested a small mediation effect of social support for mental health with marital loss. Interactions between perceived social support and marital transitions showed a strong moderating effect for men who became widowed. No significant interactions were found for women. ---------- Conclusion: Marital loss significantly decreased mental health. Increasing, or maintaining, high levels of social support has the potential to improve widowed men's mental health immediately after the death of their spouse.