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Xu S.,University of South Australia | Dogancay K.,University of South Australia | Hmam H.,DST Group
ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings | Year: 2016

This paper investigates the problem of how to optimize the path of a single moving own-ship for angle-of-arrival (AOA) target tracking in three-dimensional (3D) space. First, a novel 3D pseudolinear Kalman filter (PLKF) is proposed to reduce computational complexity and to improve stability of an extended Kalman filter solution. This filter consists of an xy-PLKF and a z-PLKF, transforming the nonlinear azimuth and elevation angle measurements into pseudolinear models. We show that when the own-ship and target are at the same height, the z-PLKF will be unbiased. Next, a gradient-descent path optimization algorithm is developed for the xy-PLKF aiming at minimizing the trace of the covariance matrix. Then, a grid search path optimization method is designed for the z-PLKF. Simulation examples verify the effectiveness of the proposed path optimization algorithm. © 2016 IEEE.

Ahamed J.,RMIT University | Joosten M.,RMIT University | Callus P.,DST Group | John S.,RMIT University | Wang C.H.,RMIT University
Composites Part A: Applied Science and Manufacturing | Year: 2016

Efficiently joining materials with dissimilar mechanical and thermal properties is fundamental to the development of strong and lightweight load-bearing hybrid structures particularly for aerospace applications. This paper presents a ply-interleaving technique for joining dissimilar composite materials. The load-carrying capacity of such a joint depends strongly on several design parameters such as the distance between ply terminations, the spatial distribution of ply terminations, and the stiffness and coefficients of thermal expansion of the composites. The effects of these factors on the strength of quasi-isotropic hybrid carbon/glass fibre composite are investigated using combined experimental, analytical and computational methods. Through fractographic analyses significant insights are gained into the failure mechanism of the hybrid joints, which are then used to aid the development of predictive models using analytical and high fidelity computational methods. To characterise the interaction between transverse matrix cracking and delamination, continuum damage mechanics model and cohesive zone model are employed. The predictions are found to correlate well with experimental data. These modelling tools pave the way for optimising hybrid joint concepts, which will enable the structural integration of dielectric windows required for multifunctional load-bearing antenna aircraft structures. © 2016 Elsevier Ltd. All rights reserved.

Shrestha A.,University of Adelaide | Spooner N.A.,University of Adelaide | Spooner N.A.,DST Group | Qiao S.Z.,University of Adelaide | Dai S.,University of Adelaide
Physical Chemistry Chemical Physics | Year: 2016

The quantum dots (QDs) of lead sulphide (PbS) are attractive near-infrared (NIR) active materials and have promising applications in a wide variety of applications. Till date many efforts have been made on optimizing its synthesis; however, current mechanistic understanding involving the nucleation and growth of these QDs has not reached the same level as that for other QDs. In this study, we present a detailed understanding on synthesis mechanism of PbS QDs so as to provide guidance for future QDs synthesis. The synthesis of PbS QDs is largely independent of classical nucleation process and the hot-injection of precursors may not be necessary for the successful synthesis of PbS QDs. The synthesis is basically a growth dominated process and is controlled by the Ostwald ripening of PbS QDs. In addition, reaction temperature and ligand are the key parameters for controlling QD growth. Temperature provides energy for overcoming activation barrier of QD growth while the ligands enhance QD growth via altering the environment for QD growth. Following the mechanism governing the synthesis of PbS QDs, we demonstrate that the size tuning of PbS QDs in ultra-small (<2 nm) can be achieved, which has been typically challenging following the hot injection synthesis. © The Owner Societies 2016.

Ahamed J.,RMIT University | Joosten M.,RMIT University | Callus P.,DST Group | Wisnom M.R.,University of Bristol | Wang C.H.,RMIT University
Materials and Design | Year: 2016

Hybridisation of multiple materials is emerging as a key strategy to achieve high performance lightweight structures while keeping the cost low. Fundamental to creating strong and cost-effective hybrid composites is the ability to efficiently join dissimilar materials. Herein we present a novel co-curing ply-overlap joint technique for integrating dissimilar composite materials. Experimental studies are conducted to identify the dominant failure mechanisms and the effect of design parameters, such as the spatial distances between ply terminations and overlap length, on the strength of hybrid composite ply-overlap joints. To enable optimisation of ply-overlap joints, analytical and computational models are developed and validated against the experimental data. The results demonstrate that ply-overlap joints are capable of approaching the un-notched strength of the glass composite material. The validated predictive tools enable design optimisation of hybrid composite structures. © 2016 Elsevier Ltd.

Grellet-Tinner G.,Flinders University | Grellet-Tinner G.,CONICET | Spooner N.A.,University of Adelaide | Spooner N.A.,DST Group | Worthy T.H.,Flinders University
Quaternary Science Reviews | Year: 2016

The iconic Australian Genyornis newtoni (Dromornithidae, Aves) is the sole Pleistocene member of an avian clade now hypothesized to be alternatively in Anseriformes or the sister group of crown Galloanseres. A distinctive type of fossil eggshell commonly found in eroding sand dunes, has been referred to Genyornis newtoni since the 1980s. The 126 by 97 mm Spooner Egg, dated at 54.7 ± 3.1 ka by optical dating of its enclosing sediments, is a complete specimen of this eggshell type that was reconstructed from fragments of a broken egg. We show that the size of the eggs from which this '. Genyornis' eggshell derives, either as predicted from measurements of fragments, or as indicated by the Spooner Egg, is unexpectedly small given the size of G. newtoni, which has an estimated mass of 275 kg, or about seven times the mass of the emu that has a similar sized egg. We compared the microstructure of the putative Genyornis eggshell to that of other dromornithids and a range of galloanseriform taxa using several microcharacterisation techniques. The '. Genyornis' eggshell displays a mosaic of oological characters that do not unambiguously support referral to any known modern bird. Its shell structure, coupled with chemical compounds in the accessory layer, makes it unlikely to have been laid by a dromornithid, whereas several characters support a megapode origin. A potential candidate for the bird that laid the putative '. Genyornis' eggs in the Pleistocene fossil avifaunal record has been ignored: Progura, a genus of extinct giant megapodes, whose species were widespread in Australia. Regression of egg size of megapodes and body mass shows that the Spooner Egg approximates the expected size for eggs laid by species of Progura. We advance the suggestion that the fossil eggshell hitherto referred to Genyornis newtoni, is more likely to have been laid by species of the giant extinct Progura. As megapodes, the species of Progura were obligate ectothermic incubators, which we suggest laid their eggs into a hole dug in sand like the modern megapode Macrocephalon maleo, thus explaining the abundant '. Genyornis' eggshell in sand dunes. Referral of this eggshell to Progura means that the fossil record of Genyornis newtoni is limited to bones and the timing of the extinction of this last dromornithid is unknown. In addition, structural similarities of eggshell in megapodes, the putative Genyornis eggshell and dromornithids, raise the possibility that these taxa are phylogenetically more closely related to each other than any is to anseriforms. Specifically, this means that dromornithids might be a sister group to galliforms rather than to or within anseriforms. © 2015 Elsevier Ltd.

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