Search PubMed⌕ Search

Biomedical subjects

A F Starr

Publications and source records attributed to A F Starr.

5 recordsLinked to original sources
PubMed2005

Gradient index metamaterials.

Metamaterials--artificially structured materials with tailored electromagnetic response--can be designed to have properties difficult or impossible to achieve with traditional materials fabrication methods. Here we present a structured metamaterial, based on conducting split ring resonators (SRRs), which has an effective index of refraction with a constant spatial gradient. We experimentally confirm the gradient by measuring the deflection of a microwave beam by a planar slab of the composite metamaterial over a range of microwave frequencies. The gradient index metamaterial may prove an advantageous alternative approach to the development of gradient index lenses and similar optics, especially at higher frequencies. In particular, the gradient index metamaterial we propose may be suited for terahertz applications, where the magnetic resonant response of SRRs has recently been demonstrated.

Journal Article↗
PubMed2004

Enhanced diffraction from a grating on the surface of a negative-index metamaterial.

We show by numerical simulation as well as by measurements on negative-index metamaterial wedge samples, that the unavoidable stepping of the refraction interface-due to the finite unit-cell size inherent to metamaterials-can give rise to a well-defined diffracted beam in addition to the negatively refracted beam. The direction of the diffracted beam is consistent with elementary diffraction theory; however, the coupling to this higher order beam is much larger than would be the case for a positive index material. The results confirm recent theoretical predictions of enhanced diffraction for negative-index grating surfaces.

Journal Article↗
PubMed1989

Automatic speech recognition for disabled people.

It has been suggested that one of the most promising areas for the application of speech recognition is in helping handicapped people (Leggett and Williams, 1984). Within the last decade, many improvements have been made in the performance of automatic speech recognisers and current technology is discussed in relation to the needs of the disabled population. Recent research developments in the field of automatic speech recognition are reviewed, with particular reference to voice control of robotic arms and environmental control units. This includes a description of a Voice Activated Domestic Appliance System (VADAS), whose evaluation has just been completed. The general conclusion reached is that although speech recognition applications for disabled people are well within the capacity of available technology, it is primarily a lack of human factors work which is impeding developments in this field. Several human factors issues are identified; the most important of these being the need to increase the reliability of present speech recognisers, before they can confidently be incorporated into the lives of the disabled population.

Journal Article↗
PubMedDate not supplied

User involvement in the early stages of the development of an aircraft warning system.

There is an increasing awareness of the importance and the benefits to be attained from consulting the end-users during system and product development. Although the rationale of utilizing the expertise of end-users in the system development life cycle appears to provide an apparently straightforward, even 'ideal' approach, there are many difficulties associated with eliciting the required knowledge from experts, both general and specific to every user group. Furthermore, many developers do not know how to involve users, or if they do, they do not utilize them to best effect. In the avionics sphere, the wealth of knowledge possessed by line pilots and flight engineers represents a vital information resource for the design of future flight-deck systems. As a specific example, this paper overviews some of the considerations which arose from working with these end-users in the early stages of the development of a warning and diagnostic system for civil aircraft. The end-goal of this particular phase of the work was the generation of guidelines for the design of the interface for the software engineers to use when building the prototype, and the methodological approach taken to achieve this is reported here.

Aircraft↗