Energy Based Control System Designs for Underactuated Robot Fish Propulsion

In nature through millions of years of evolution fish and cetaceans have developed fast efficient and highly manoeuvrable methods of marine propulsion. A recent explosion in demand for sub sea robotics, for conducting tasks such as sub sea exploration and survey has left developers desiring to capture some of the novel mechanisms evolved by fish and cetaceans to increase the efficiency of speed and manoeuvrability of sub sea robots. Research has revealed that interactions with vortices and other unsteady fluid effects play a significant role in the efficiency of fish and cetaceans. However attempts to duplicate this with robotic fish have been limited by the difficulty of predicting or sensing such uncertain fluid effects. This study aims to develop a gait generation method for a robotic fish with a degree of passivity which could allow the body to dynamically interact with and potentially synchronise with vortices within the flow without the need to actually sense them. In this study this is achieved through the development of a novel energy based gait generation tactic, where the gait of the robotic fish is determined through regulation of the state energy rather than absolute state position. Rather than treating fluid interactions as undesirable disturbances and `fighting' them to maintain a rigid geometric defined gait, energy based control allows the disturbances to the system generated by vortices in the surrounding flow to contribute to the energy of the system and hence the dynamic motion. Three different energy controllers are presented within this thesis, a deadbeat energy controller equivalent to an analytically optimised model predictive controller, a $H_\infty$ disturbance rejecting controller with a novel gradient decent optimisation and finally a error feedback controller with a novel alternative error metric. The controllers were tested on a robotic fish simulation platform developed within this project. The simulation platform consisted of the solution of a series of ordinary differential equations for solid body dynamics coupled with a finite element incompressible fluid dynamic simulation of the surrounding flow. results demonstrated the effectiveness of the energy based control approach and illustrate the importance of choice of controller in performance

Elevation leads to altruistic behavior.

Feelings of elevation, elicited by witnessing another person perform a good deed, have been hypothesized to motivate a desire to help others. However, despite growing interest in the determinants of prosocial behavior, there is only limited evidence that elevation leads to increases in altruistic behavior. In two experiments, we tested the relationship between elevation and helping behavior. Prior to measuring helping behavior, we measured elevation among participants in an elevation-inducing condition and control conditions in order to determine whether witnessing altruistic behavior elicited elevation. In Experiment 1, participants experiencing elevation were more likely to volunteer for a subsequent unpaid study than were participants in a neutral state. In Experiment 2, participants experiencing elevation spent approximately twice as long helping the experimenter with a tedious task as participants experiencing mirth or a neutral emotional state. Further, feelings of elevation, but not feelings of amusement or happiness, predicted the amount of helping. Together, these results provide evidence that witnessing another person's altruistic behavior elicits elevation, a discrete emotion that, in turn, leads to tangible increases in altruism

Biologically reinforced geopolymer composites

A series of studies detailing the characteristics of biologically reinforced geopolymers is presented. Cork particle reinforced sodium geopolymer composites were shown to have a maximum flexural strength of 2.5 MPa, and an average strain-to-failure of 0.75%. Abaca fiber reinforced sodium geopolymer composites had flexural strengths exceeding 25 MPa. The main focus of this study was abaca fiber reinforced potassium geopolymer composites, which had flexural strengths exceeding 50 MPa at 8 wt% abaca fibers. This new composite was shown to have good water and saltwater durability, decent sodium hydroxide and freeze cycle durability, and poor sulfuric acid durability. The composite was also tested for heat sensitivity, and showed a steady decrease in flexural strength as it was exposed to higher temperatures. The composite was unable to carry any load after being treated to 300°C. Weibull statistical analysis was used to better understand the range of flexural strengths within different sample groups. Finally, SEM analysis was employed to characterize fracture surfaces and mode of failure in the different sample sets

Evaluating the use of lithium sulphur batteries for a deep ocean pressure balanced AUV energy source

Lithium sulphur batteries offer a huge potential advantage over established AUV energy sources, such as Lithium polymer or Lithium ion batteries. The high energy density and low specific gravity make them an ideal choice for pressure balanced systems which could significantly improve AUV endurance. This paper aims to evaluate the current technology readiness for deployment in the AUV industry

Problem and treatment of DC offsets in FDTD simulations

Journal ArticleThis paper discusses the causes of and some solutions to the commonly observed problem of dc field offsets in finite-difference time-domain (FDTD) simulations. DC electric and magnetic field offsets are shown to be valid calculated responses of the modeled systems, resulting from interaction between the turn-on characteristics of the source and the properties of the models. The dc offsets may be avoided in the time domain by tailoring the source waveforms or in the frequency domain by post-processing the FDTD output

Examining the Relationship between Brand Emotion and Brand Extension among Supporters of Professional Football Clubs

Purpose: There is debate and controversy about the use of branding in sport. Often, fans show loyalty to their club that many brands could only dream of, and a key argument of previous research is that supporters do not like to think of their club in commercial terms, as a brand (Chadwick and Beech, 2007; Chadwick and Holt, 2006). However, we argue that in today’s environment fans have a pragmatic attitude towards the necessity of branding and its importance in the future success of their clubs. Thus a model conceptualising the relationship between supporters’ emotional attachment, supporters’ brand perception/strength and their support for brand extension was developed and tested. Methodology: In-depth interviews with, players, clubs’ officials and supporters, leading to the design of a survey instrument completed by 852 supporters of two professional Norwegian football clubs. Findings: The model confirms that fans that have a strong emotional attachment to their club have a stronger perception of the club as a brand and support brand extension. Research limitations: This is a one country study. Practical implications: Club management needs to be careful when extending its brand. Brand extension must be designed to reflect the heritage and tradition of the club. Also, club management needs to show in brand extension an element of competitiveness which improves brand image, strengthens supporters’ belief in their club and attracts new supporters. Originality/value: We provide new evidence which contradicts existing theory. The study challenged the widely accepted argument that supporters of football clubs are likely to disapprove of and reject the thought of their favourite football club as a brand

‘How the Other Half Live’: Poor and Rich Citizenship in Austere Welfare Regimes

A growing body of research quantifies the recent impact of fiscal consolidation and public service reform in liberal welfare regimes. However, less is known about how this is affecting the common terms upon which citizenship status is granted and experienced. With this in mind, this article examines what bearing the political crafting of welfare austerity is having on the status, rights and identity of notionally equal citizens. To do so, this article draws on a qualitative study examining lived experiences of poor and rich citizenship in New Zealand and the UK. Despite policy programmes idiosyncratic to their institutional context, both countries exhibit a similarly bifurcated system of social citizenship that is serving to structure, rather than moderate, material and status inequalities in austere welfare regimes

Genetic dissection of triplicated chromosome 21 orthologs yields varying skeletal traits in Down syndrome model mice

Down syndrome (DS) phenotypes result from triplicated genes, but it is generally unknown how specific three copy human chromosome 21 (Hsa21) orthologous genes or interactions between genes affect these traits. A mouse mapping panel genetically dissecting Hsa21 syntenic regions was used to investigate the contributions and interactions triplicated Hsa21 orthologous genes on mouse chromosome 16 (Mmu16). Four-month-old femurs of male and female Dp9Tyb, Dp2Tyb, Dp3Tyb, Dp4Tyb, Dp5Tyb, Dp6Tyb, Ts1Rhr, and Dp1Tyb;Dyrk1a+/+/- mice were analyzed by micro-computed tomography and 3-point bending to assess skeletal structure and mechanical properties. Male and female Dp1Tyb mice, with the entire Hsa21 homologous region of Mmu16 in three copies, display specific bone deficits similar to humans with DS and were used as a baseline comparison for the other strains in the panel. Bone phenotypes varied based on triplicated gene content, sex, and bone compartment. Three copies of Dyrk1a played a sex-specific, essential role in trabecular deficits and may interact with other genes to influence cortical deficits related to DS. Triplicated genes in Dp9Tyb and Dp2Tyb mice improved some skeletal deficits. As triplicated genes may both improve and worsen bone deficits, it is important to understand the interaction between and molecular mechanisms of skeletal alterations affected by these genes

An outbreak investigation of paediatric severe acute respiratory infections requiring admission to intensive care units - Fiji, May 2016

Introduction Influenza-associated severe acute respiratory infections (SARI) are a major contributor to global morbidity and mortality. In response to a cluster of SARI cases and deaths in pregnant women, with two deceased cases testing positive for influenza A(H1N1)pdm09, an investigation was initiated to determine whether there was an increase of paediatric SARI cases admitted to divisional hospital intensive care units in Fiji in may 2016 compared to May 2013-2015. Methods Retrospective case finding was conducted at the paediatric intensive care units (PICUs) in Fiji's three divisional hospitals. Data were collected from 1 January 2013 to 26 May 2016. Cases were identified using a list of clinical diagnoses compatible with SARI. Results A total of 632 cases of paediatric SARI with complete details were identified. The median age of cases was 6 months (Interquartile range: 2-14 months). Children aged less than 5 years had a higher rate of paediatric SARI requiring admission to a divisional hospital PICU in May 2016 compared to May 2013-2015 (Incidence rate ratio: 1.7 [95% CI: 1.1-2.6]). This increase was not observed in children aged 5-14 years. The case-fatality ratio was not significantly different in 2016 compared to previous years. Conclusion The investigation enabled targeted public health response measures, including enhanced SARI surveillance at divisional hospitals and an emergency influenza vaccination campaign in the Northern Division

Medusan Morphospace: Phylogenetic Constraints, Biomechanical Solutions, and Ecological Consequences

Medusae were the earliest animals to evolve muscle-powered swimming in the seas. Although medusae have achieved diverse and prominent ecological roles throughout the world\u27s oceans, we argue that the primitive organization of cnidarian muscle tissue limits force production and, hence, the mechanical alternatives for swimming bell function. We use a recently developed model comparing the potential force production with the hydrodynamic requirements of jet propulsion, and conclude that jet production is possible only at relatively small bell diameters. In contrast, production of a more complex wake via what we term rowing propulsion permits much larger sizes but requires a different suite of morphological features. Analysis of morphometric data from all medusan taxa independently confirms size-dependent patterns of bell forms that correspond with model predictions. Further, morphospace analysis indicates that various lineages within the Medusozoa have proceeded along either of two evolutionary trajectories. The first alternative involved restriction of jet-propelled medusan bell diameters to small dimensions. These medusae may be either solitary individuals (characteristic of Anthomedusae and Trachymedusae) or aggregates of small individual medusan units into larger colonial forms (characteristic of the nectophores of many members of the Siphonophorae). The second trajectory involved use of rowing propulsion (characteristic of Scyphozoa and some hydromedusan lineages such as the Leptomedusae and Narcomedusae) that allows much larger bell sizes. Convergence on either of the differing propulsive alternatives within the Medusozoa has emerged via parallel evolution among different medusan lineages. The distinctions between propulsive modes have important ecological ramifications because swimming and foraging are interdependent activities for medusae. Rowing swimmers are characteristically cruising predators that select different prey types from those selected by jet-propelled medusae, which are predominantly ambush predators. These relationships indicate that the different biomechanical solutions to constraints on bell function have entailed ecological consequences that are evident in the prey selection patterns and trophic impacts of contemporary medusan lineages