Response‐correction‐based fault detection in small linear microstrip patch arrays using magnitude‐only far‐field pattern samples

We present a computationally efficient method for detecting faulty elements in a small linear microstrip patch array from samples of the array's far‐field magnitude radiation pattern (here represented by realistic EM simulations). Regardless of the array size, our method requires only one expensive full‐wave entire‐array simulation—compared to, e.g., the 696 required by the previous best method (Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775–777) for a 16‐element array. This one simulation gives the accurate far‐field magnitude pattern of the original defect‐free array, and is used in conjunction with the defect‐free array's analytical array factor to formulate a response correction function, which can then be used to construct an accurate approximation of the EM‐simulated pattern of any arbitrary faulty array at very low cost. The low cost and high accuracy of these approximations make possible an enumeration strategy for identifying the faulty elements, which would have been computationally prohibitive were EM‐simulated patterns to be used. Our method was robust in handling arrays of double the size considered in Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775–777, while expanding on (Patnaik et al., IEEE Trans Antennas Propag 55 (2007), 775–777) by also addressing partial faults and measurement noise. Accuracies in detecting up to three faults (including partial ones) in arrays of 16 and 32 elements exceeded 97% under noise‐free conditions, and were above 93% in the presence of 2 dB measurement noise. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:683–689, 2016.     

Silence detection for multimedia communication systems

Silence detection and removal is an essential building block of any multimedia video conferencing system. It reduces the bandwidth requirements of the underlying network transport service and helps to maintain an acceptable end-to-end delay for audio. We analyze the requirements for a silence detection algorithm hosted on a multimedia communication system, and propose a novel low-complexity algorithm operating in the non-linear domain. After discussing the constraints which are imposed by the architecture of the system hardware (computer, packet-based network), we show that several recently proposed silence detection algorithms fail to meet all of these constraints. A new approach is then introduced, based on the small- and large-signal behavior of the speech waveform in the -law domain. The new algorithm is compared with a recent design that meets several of our requirements; experimental results indicate that it performs significantly better in the particular environment at hand.     

Fast change of basis in algebras

Given ann-dimensional algebraA represented by a basisB and structure constants, and given a transformation matrix for a new basisC., we wish to compute the structure constants forA relative to C. There is a straightforward way to solve this problem inO(n ⁵) arithmetic operations. However given an O(n ) matrix multiplication algorithm, we show how to solve the problem in time O(n ₊₁). Using the method of Coppersmith and Winograd, this yields an algorithm ofO(n ^3.376).This research was partially supported by NSF Grant #CCR8905534     

The Language of Resilience: Ideas and Action in Contemporary Policy-making

ABSTRACT

It is difficult not to have noticed that in the last decade or so the notion of resilience has been adopted by many practitioners in Anglophone nations as part of a strategy for political engagement. Very often, those who advocate a resilience agenda concede that the insidious effects of globalized forms of capitalism cannot effectively be resisted and therefore it is necessary to accommodate to this reality by adapting and becoming resilient to any shocks that might arise. The aims of this paper are to explore not only some of the reasons why resilience has such appeal, but also to make some critical observations about policy responses at a time of increasing uncertainty. Amongst the questions addressed are: what might the use of resilience by policy-makers reveal about the conduct of government? Can its popularity within government agencies provide some insights as to why tangible reform remains elusive? Is there a form of resilience strategy that could serve to counter the pernicious effects of austerity and neoliberal policy responses? Amongst the arguments proposed is that, at best, resilience has only limited utility and at worst serves as a distraction to developing more incisive and lasting forms of political engagement.     

Book reviews

Housing Finance in the 1990s. C. Whitehead & B. Turner (Eds)National Swedish Institute for Building Research, Gavle, 1993, 330 pp., ISBN 91–7111–068–2

Markets and Managers—New Issues in the Delivery of Welfare. Peter Taylor Gooby & Robyn Lawson (Eds) Buckingham, Open University Press, 1993, 190 pp., £37.50 hardback, £12.99 paperback

Housing Finance and Subsidies in Britain. Duncan Maclennan & Kenneth Gibb (Eds) Aldershot, Avebury, 1993, 218 pp., £35

The Estate Action Initiative: Council Housing Renewal, Management and Effectiveness. Ricardo Pinto Aldershot, Avebury, 1993, 286 pp., £35

Keeping to the Marketplace: the Evaluation of Canadian Housing Policy. John C. Bacher Montreal and Kingston, McGill‐Queens University Press, 1993, 327 pp., C$55.00, £42.45 UK

The Reform of Housing in Eastern Europe and the Soviet Union. B. Turner, J. Hegedüs & I. Tosics London, Routledge, 1992, 362 pp., £45 hardback

Neighbour Disputes: Responses by Social Landlords. Valerie Karn, Rachel Liskinn, David Hughes & John Cawley Coventry Institute of Housing, 1993, 158 pp.     

Book reviews

Theories of Urban Politics. David Judge, Gerry Stoker & Harold Wolman (Eds). London, Sage, 1995, 310 pp. £11.99 pb. ISBN: 0 8039 8865 6

The Faces of Homelessness in London. Jeanne Moore, David Canter, Des Stockley & Madeline Drake. Aldershot, Dartmouth, 1995, 339 pp, £30.00. ISBN: 1 85521 252 8

Housing, ‘Race’, Social Policy and Empowerment. Malcolm Harrison. Aldershot, Avebury, 1995, 176 pp., £32.50. ISBN: 1 85628 860 9

Empowerment and Estate Regeneration: A Critical Review. Murray Stewart & Marilyn Taylor. Bristol, Policy Press 1995, 90 pp., £11.95. ISBN: 1 86134 001 X

Old and Homeless—Double Jeopardy. Diane Wiatt Rich, Thomas Rich & L. C. Mullins (Eds). Connecticut, Auburn House, 1995, 142 pp., £39.95. ISBN 0 86569 246 7

Building the Workingman's Paradise: The Design of American Company Towns. Margaret Crawford. London and New York, Verso, 1995, 248 pp., £44.95. ISBN: 0 86091 4216     

A sensitivity study for the visualisation of bacterial weathering of concrete and stone with computerised X-ray microtomography

Geologists and engineers recently have adopted computerised X-ray microtomography (microCT), a radiological imaging technique, for geological and petrophysical applications such as the assessment of sediment characteristics, CT-measurement of compressibility and compaction, multiphase flow studies, measurement of bulk density and moisture content, and of porosity and permeability. This study focuses on another application: the monitoring of biological weathering of natural building stones and concrete. Microbial activity as a determining factor in the deterioration process of building materials has a major economic impact. Because of its non-destructive character, microCT could be the ideal monitoring technique. With this technique, three-dimensional (3D) images of the entire inner structure of the material can be obtained, together with quantitative data. In depth changes of porosity of concrete and stone specimens due to bacterial weathering were assessed in this work. Also, porosity was visualised based on 3D data with homemade software. Scanning electron microscopy (SEM) images provided additional information and supported conclusions drawn from the X-ray microCT data. Resolution improvement will make the study of petrophysical aspects of physical weathering and/or biological deterioration processes of natural building stones and concrete a promising subject for further microCT-application.