Polarisation-insensitive, near-travelling-wave semiconductor laser amplifiers at 1.5 mu m

A polarisation-insensitive, near-travelling-wave semiconductor laser amplifier (TWSLA) is presented. Polarisation sensitivity of less than 1 dB is demonstrated. This may be the lowest reported polarisation sensitivity for a TWSLA. In addition, the saturated output power is in excess of 5.2 dBm.<>     

A parallel median algorithm

We give a deterministic algorithm for finding the kth smallest item in a set of n items, running in O((log log n)²) parallel time on O(n) processors in Valiant's comparison model.     

A method for interconnecting heterogeneous computer networks

The real problems of network interconnection lie in the management of heterogeneity. The heterogeneity is not confined to the mechanical protocols but to much wider issues such as service philosophy (connection-orientated vs connectionless), addressing, routing, applications models, management facilities and the foresight of the network designers in allowing for interconnection with alien networking systems. This paper describes a system which interconnects two heterogeneous networking environments through a third (local) system. Application layer relaying was chosen to provide the services of computer mail and remote terminal access. The interconnection architecture uses special network front-ends and a local area network to provide a flexible and manageable system. A transport service interface is used to provide functional separation between the front-ends and general purpose computers, including the relays.     

Conclusions from CALtastrophes

What are the barriers to the widespread introduction of computer aided teaching? Information is collected from a large scale observational study of over 150 lessons which involved CAL, together with reports from 30 teachers who look part in an in-service training course which introduced them to CAL. Examples of problems encountered are classified under five headings: acquiring a reliable computer, setting it up so the whole class can see it, choosing software, learning to drive it and integrating it into the lesson and the curriculum. Conclusions are drawn about how to overcome these problems, in the form of advice to teachers, advisors and LEAs, and lessons for software designers. CAL is not likely to become widespread unless we act on the lessons we have drawn from these observations, and indeed, unless those of us who are responsible for educational innovation set up a dialogue between teachers and software designers.     

Rainfall attenuation at 36 GHz and 55 GHz

Simultaneous rainfall measurements at 36 GHz and 55 GHz on a common 4.1 km path show, under the conditions of these experiments, that the attenuation due to rainfall lies between the attenuation values predicted by the lognormal and the Best rain drop size distributions.     

THE MYCOFLORA OF BARLEYS ACCEPTED AND REJECTED FOR MALTING

Barleys were examined by direct and dilution plating before purchase for drying and subsequent malting. The mould flora of barleys rejected because of heating was characterised by lower proportions of field fungi, particularly Cladosporium spp, and higher proportions of storage fungi, particularly Aspergillus glaucus (group), than in undried barleys which had not heated. Results indicated that microbiological analysis could be used to resolve whether self-heating of undried barley has occurred on the farm before the barley has been delivered free of heat to meet a purchaser's specification.     

The future of the microcomputer as a classroom teaching aid: An empirical approach to crystal gazing

A microcomputer can be a valuable teaching aid but its current use in secondary schools is so infrequent as to make it difficult to assess its future potential. We observed 174 school lessons during which 17 teachers employed a microcomputer regularly with a chosen class for a whole term. The aim was to provide a glimpse into the future when there will be better computer facilities and more expertise among teachers. During the term, we detected no drop in interest as the novelty diminished and lessons tended to improve as teachers became more experienced in using the medium. Two terms later the majority of teachers were still using a microcomputer regularly as a teaching aid and there was some spread of interest to other teachers in the same schools. The results suggest that, in subjects like mathematics, computer-aided teaching will be successfully adopted by the majority of teachers if the necessary resources are available. The computer appears to be a very versatile teaching aid and we found no grounds for strongly recommending any particular style of use.     

A cost-effective eigensolution method for large systems with Rockwell NASTRAN

The Lanczos method with reorthogonalization based on Householder transformations has been implemented in Rockwell's version of the COSMIC-released NASTRAN program for partial solution of a large-scale symmetric eigenvalue problem. A special technique has been included for restarting Lanczos iteration with a new random vector, partly to avoid premature termination associated with a null or linearly dependent Lanczos feed vector and partly to discover multiple eigenvalues. The developed Lanczos-Householder algorithm with built-in random restart capability shows appreciable cost-savings over the conventional subspace iteration technique as well as the COSMIC NASTRAN method, FEER, which utilizes the modified Gram-Schmidt process to reorthogonalize the Lanczos feed vector with respect to those previously converged.