Australian National University

About: Australian National University is a education organization based out in Canberra, Australian Capital Territory, Australia. It is known for research contribution in the topics: Population & Galaxy. The organization has 34419 authors who have published 109261 publications receiving 4315448 citations. The organization is also known as: The Australian National University & ANU.

Stable adaptive observers for nonlinear time-varying systems

Abstract: An adaptive observer/identifier for single input/single output observable nonlinear systems that can be transformed to a certain observable canonical form is described. Sufficient conditions for stability of this observer are provided. These conditions are in terms of the structure of the system and canonical form, the boundedness of the parameter variations, and the sufficient richness of some signals. The scope of the canonical form and the use of the observer/identifier is motivated by the presentation of applications to time-invariant bilinear systems, nonlinear systems in phase-variable form a biotechnological process, and a robot manipulator. In each case, the specific stability conditions are presented. >

Ultrasensitive hyperspectral imaging and biodetection enabled by dielectric metasurfaces

Abstract: Metasurfaces based on resonant subwavelength photonic structures enable novel ways of wavefront control and light focusing, underpinning a new generation of flat-optics devices1. Recently emerged all-dielectric asymmetric metasurfaces, composed of arrays of metaunits with broken in-plane inversion symmetry2–7, exhibit high-quality resonances originating from the intriguing physics of bound states in the continuum. Here, we combine dielectric metasurfaces and hyperspectral imaging to develop an ultrasensitive label-free analytical platform for biosensing. Our technique can acquire spatially resolved spectra from millions of image pixels and use smart data-processing tools to extract high-throughput digital sensing information at the unprecedented level of less than three molecules per μm2. We further show spectral data retrieval from a single image without using spectrometers, enabled by our unique sensor design, paving the way for portable diagnostic applications. This combination of nanophotonics and imaging optics extends the capabilities of dielectric metasurfaces to analyse biological entities and atomic-layer-thick two-dimensional materials over large areas. Spatially resolved spectra from millions of pixels and information extraction from three molecules per μm2 is now possible using dielectric metasurfaces.

Recursive estimation of mixed autoregressive-moving average order

Abstract: SUMMARY The order, (p, q), of an autoregressive-moving average sequence, y(t), may be estimated- by minimizing a criterion, log &2 + (p + q) log T/T, with respect to p and q, where ^2 is the maximum likelihood estimate of the variance of the innovations, ?(t). It is suggested that, instead, a2 be estimated from a series of regressions of y(t) on y(t-1),y(t-2),...,y(t-p), 5(t-1),...,?(t-q), where the ?(t) are obtained by fitting a long autoregression to the data. It is shown how the sequence of regressions may, for p = q, be economically recursively calculated by embedding them in a sequence of bivariate autoregressions. Asymptotic properties of the procedure are established under very general conditions.