We present ongoing work to develop a power transformer condition monitoring system. Energy harvesting will be used to power the sensor nodes measuring the vibration of the transformer. A subset of this work will be demonstrated.

The uniformly most powerful invariant (UMPI) test is derived for detecting a target with unknown location in a noise sequence. This test has the property that for each possible target location it has the greatest power of all tests which are invariant to cyclic permutations of the observations. The test is compared to the generalised likelihood ratio test (GLRT), which is commonly used as a solution to this detection problem. Monte-Carlo simulations show that the powers of the two tests are comparable, thereby justifying near-optimality of the GLRT.

Fractal image compression is a technique based on the representation of an image by a contractive transform, on the space of images, for which the fixed point is close to the original image. This broad principle encompasses a very wide variety of coding schemes, many of which have been explored in the rapidly growing body of published research. While certain theoretical aspects of this representation are well established, relatively little attention has been given to the construction of a coherent underlying image model that would justify its use. Most purely fractal-based schemes are not competitive with the current state of the art, but hybrid schemes incorporating fractal compression and alternative techniques have achieved considerably greater success. This review represents a survey of the most significant advances, both practical and theoretical, since the publication of Jacquin's (1990) original fractal coding scheme.

The EM algorithm is a commonly cited solution in the literature for the problem of maximum likelihood estimation of covariance matrices under a Toeplitz constraint. In this paper, the solution is extended to the case of two-dimensional signals, where spatial stationarity enforces a Toeplitz-block-Toeplitz structure on the covariance matrix. A further generalisation which is presented involves the estimation of the covariance when the observations are subject to subspace interference. It is shown that this situation is amenable to a missing data interpretation, and can be incorporated into the EM iteration with moderate ease. The solution shares all the characteristics of the I-D Toeplitz estimate. The need to solve this problem arises in many invariance applications, where it is required to fit a stationary multivariate normal model to data which is subject to a certain type of interference. The case of unknown DC offset is included in this class.

This paper describes an active vision approach to rock recognition for the purpose of measuring rock size distributions or fragmentation. Such a measure is useful in the mining industry to facilitate the control and monitoring of autogenous mills. A new approach for recognising and segmenting rock images is described. It is based on rapid identification of targets at which attention is focused for analysis. In addition, a multiscalar image pyramid is used in a novel way to allow target detection and analysis to be optimised for a particular size, thereby improving their performances. The results that have been obtained with this approach are both robust and accurate.

Traditional block transform image coding systems generate artifacts near block boundaries which degrade low bit rate coded images. To reduce these artifacts, a class of unitary transformations, called lapped orthogonal transforms (LOT), is investigated. The basis function on which the signal is projected are overlapped for adjacent blocks. An example of an LOT optimized in terms of energy compaction is numerically derived, using an augmented Lagrangian optimization algorithm. Using this LOT, intraframe coding experiments for 256*240 pixel images were performed at bit rates between 0.1 and 0.35 bits/pixel. The LOT improved the coded image subjective quality over other transforms. The LOT was also used in interframe full-motion video coding experiments for head and shoulder sequences at 28 and 56 kb/s. Significant improvement resulted at low data rates and if no motion compensation were used. However, the improvement was no longer significant at 56 kb/s with full motion compensation.>