DOI:10.1049/ecej:19910001

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper describes the architecture, facilities and usage of the London University interactive video education network (LIVE-NET), which connects a number of sites in the University. The extension of the reach of the network by use of a direct broadcast satellite (DBS) is described. The paper discusses how the video facilities are being supplemented by interactive digital services, and how packet video is being used to link the network to others in the USA. Finally the paper considers the administrative support which is provided to assist operations.

DOI:10.1049/ecej:19910003

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The paper discusses the current status of passive millimetre wave radiometry as an imaging technique. The major problems are poor spatial resolution and lack of thermal sensitivity. Techniques for overcoming these difficulties are identified, including the use of aperture synthesis, multichannel receivers, correlation and inverse transform techniques.

DOI:10.1049/ecej:19910004

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Computer and data networks are the mechanism by which information systems are interconnected. The underlying techology and the principles of design for the architectures of such networks are still limited but the demands placed upon them are of continually increasing sophistication. The paper reviews the ways in which a classification of networks can be determined, thereby providing a perspective for the designers of modern communication networks. It is the classification of networks (based upon wide-area networks, metropolitanarea networks and local-area networks) which causes great confusion and so the paper sets out to explain how the ‘spirit’ of classification should be used and not necessarily the ‘law’ in order to appreciate the characteristics of the various types of network.

DOI:10.1049/ecej:19910005

出版商:IEE    

年代:1991

数据来源: IET

摘要:

The requirement for improved picture quality in videophone and videoconference systems operating at low bit-rates has stimulated interest in model-based image coding. In this paper, two model-based coding techniques are described which are capable of producing either improved picture quality at bit-rates around 64 kbit/s or acceptable picture quality at bit-rates far lower than 64 kbit/s. The first technique produces facial expressions by using feature code-books; the second technique produces facial expressions by distorting an underlying three-dimensional model. The problems of image analysis and synthesis, which are concomitant in model-based coding, are discussed.

DOI:10.1049/ecej:19910006

出版商:IEE    

年代:1991

数据来源: IET

摘要:

Transformation of a segment of acoustic signal, by processing into a vectorial representation such as the spectrum, can permit the identification of the constituent phonemes within spoken speech. Subsequent comparison against a previously stored representation using techniques such as dynamic time warping or hidden Markov modelling then permits a speech recognition operation to be accomplished. These signal-processor-intensive transform and graph-search-based pattern-matching techniques are reviewed and currently achievable recognition accuracies are reported.

DOI:10.1049/ecej:19910007

出版商:IEE    

年代:1991

数据来源: IET