Defence Science and Technology Organisation

About: Defence Science and Technology Organisation is a nonprofit organization based out in Canberra, Australian Capital Territory, Australia. It is known for research contribution in the topics: Radar & Clutter. The organization has 2465 authors who have published 3856 publications receiving 90614 citations.

Thermoelastic stress analysis with a compact low-cost microbolometer system

Abstract: This article describes the development and validation of a novel thermoelastic stress analysis (TSA) system based on a low-cost microbolometer device. The use of a microbolometer for a highly synchronous and delicate temperature measurement breaks a longstanding and exclusive reliance on high performance, cooled photon detectors for thermoelastic applications. It is shown that despite markedly inferior noise equivalent temperature detectivity and dynamic response specifications, microbolometers are capable of achieving comparable levels of stress measurement performance. The practical implications for experimental stress analysis are significant. Microbolometers are relatively low in capital cost, small in size, have good tolerance to shock and vibration and consume less power than their photon counterparts, attributes that confer enormous practical advantages. It is argued that the emergence of TSA systems that are more affordable and better suited to in-service application could help to promote a much b...

Adaptive cancellation of nonstationary interference in HF antenna arrays

Abstract: The paper statistically analyses and compares temporal variability in the spatial structure of two HF interference signals propagated from known locations via ionospheric channels with different spatial and temporal characteristics. The impact of the particular ionospheric paths propagating HF interference on the cancellation performance of various adaptive beamforming algorithms is investigated using data collected by the receiving antenna array of the Jindalee Facility Alice Springs OTH radar in Alice Springs, Australia. Measurements and analysis statistically confirm that the spatial properties of HF interference signals, and the actual performance improvements gained through the use of adaptive beamforming techniques, are highly dependent on the spatio-temporal characteristics of the prevailing ionospheric circuits linking the particular source location to the receiving array at the selected operating frequency.

Modeling Compressive Skin Failure of Sandwich Composites in Fire

Abstract: A thermal-mechanical model is presented for calculating the residual compressive strength of flammable sandwich composite materials in fire. The model can also estimate the time-to-failure of the laminate face skin to sandwich composites exposed to fire. The model involves a two-stage analysis: thermal modeling and mechanical modeling. The thermal component of the model predicts the temperature profile and amount of decomposition through sandwich composites exposed to one-sided heating by fire. The mechanical component of the model estimates the residual compressive strength of the sandwich composite and the onset of skin failure. The model is tested for sandwich composite materials with combustible glass/ vinyl ester skins and balsa core. Experimental fire tests are performed on the sandwich composites under combined compressive loading and one-sided heating at constant heat flux levels between 10 kW/m 2 (Tmax · 250°C) and 50 kW/m2 (·600°C). The model predicts that the time-to-failure increases with the ...

Hybrid Poisson and multi-Bernoulli filters

Abstract: The probability hypothesis density (PHD) and multi-target multi-Bernoulli (MeMBer) filters are two leading algorithms that have emerged from random finite sets (RFS). In this paper we study a method which combines these two approaches. Our work is motivated by a sister paper, which proves that the full Bayes RFS filter naturally incorporates a Poisson component representing targets that have never been detected, and a linear combination of multi-Bernoulli components representing targets under track. Here we demonstrate the benefit (in speed of track initiation) that maintenance of a Poisson component of undetected targets provides. Subsequently, we propose a method of recycling, which projects Bernoulli components with a low probability of existence onto the Poisson component (as opposed to deleting them). We show that this allows us to achieve similar tracking performance using a fraction of the number of Bernoulli components (i.e., tracks).

Recursive state estimation for multiple switching models with unknown transition probabilities

Abstract: This work considers hybrid systems with continuous-valued target states and discrete-valued regime variable. The changes (switches) of the regime variable are modeled by a finite state Markov chain with unknown and random transition probabilities following Dirichlet distributions. Our work analytically derives the marginal posterior distribution of the states and regime variables, the transition probabilities being integrated out. This leads to a variety of recursive hybrid state estimation schemes which are an appealing intuitive and straightforward extension of standard algorithms. Their performance is illustrated by a maneuvering target tracking example.