It is difficult to define precisely what is meant by an explanation. The author therefore assumes that explanations provide information that people need and provide answers to questions which people ask when they are ...
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It is difficult to define precisely what is meant by an explanation. The author therefore assumes that explanations provide information that people need and provide answers to questions which people ask when they are learning about some new area of interest. Three major points are addressed: what is needed for explanations for ITSs, what is currently available and how to begin to provide what is needed.< >
Phased arrays are a major class of antennas which offer many important features such as electronic beam scanning. Their flexibility has to be assessed against their complexity and cost. The fundamental principles of a...
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Phased arrays are a major class of antennas which offer many important features such as electronic beam scanning. Their flexibility has to be assessed against their complexity and cost. The fundamental principles of a phased array are described. The properties of radiating apertures are given first, as these are basic to both aperture antennas and arrays as sampled apertures. Linear array analysis then introduces beam steering and null steering. Array beamforming shows how array excitation is controlled. This is followed by discussion of the effects of systematic or random excitation errors. Planar array analysis includes different array grid structures and the important topic of mutual coupling. Finally active arrays are briefly introduced.< >
MESAR (Multifunction Electronically Scanned Adaptive Radar) is an experimental phased array radar which exploits recent advances in technology to reduce cost and realize the potential of phased array radar to a far gr...
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MESAR (Multifunction Electronically Scanned Adaptive Radar) is an experimental phased array radar which exploits recent advances in technology to reduce cost and realize the potential of phased array radar to a far greater extent than has so far been achieved. It employs a solid state active array and has a digital beamformer together with programmable waveform generation and signal processing. MESAR is a collaborative and jointly funded venture between Plessey Radar and the Admiralty Research Establishment and has been in development since 1982.< >
Discusses some factors which a radar designer should consider in assessing which type of phased array system (if any) to employ, and outlines some fundamental antenna characteristics which may influence the radar desi...
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Discusses some factors which a radar designer should consider in assessing which type of phased array system (if any) to employ, and outlines some fundamental antenna characteristics which may influence the radar design. The principal functions required from primary radar are general surveillance, target tracking, and non-co-operative target identification. In situations where space is at a premium, as in ships, it is desirable to provide all these functions in one radar. The fully-active, beam-agile array with a comprehensive selection of transmitter modulations appears to be an ideal solution, apart from cost.< >
With recent developments, the array designer now has the option of placing active elements at the array face for both transmit and receive functions, and to perform digitally programmable operations on the signals at ...
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With recent developments, the array designer now has the option of placing active elements at the array face for both transmit and receive functions, and to perform digitally programmable operations on the signals at each element. The spatial filtering functions required of the array; and the techniques and architectures which are available for their realisation are examined. Attention is focussed on the receiving function of the array, since this is generally more demanding in terms of the number of beams to be generated and their sidelobe performance than the transmit function.< >
Reviews application of optical signal distribution in phased arrays. Properties of the fibre transmission medium are described. The performance of optical sources and detectors is reviewed, leading to calculations of ...
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Reviews application of optical signal distribution in phased arrays. Properties of the fibre transmission medium are described. The performance of optical sources and detectors is reviewed, leading to calculations of loss and signal to noise ratio for the complete distribution system. Novel beam forming networks using dispersive and nondispersive optical fibre trees are introduced. Optically controlled microwave devices are described and their application to phased arrays discussed. The paper concludes with an assessment of the current status of optically controlled phased arrays and predictions of future trends.< >
A method of designing intelligent tutoring systems (ITS) is described which stresses the importance of providing the user with knowledge about a given problem-domain before problem solving skills are put to the test. ...
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A method of designing intelligent tutoring systems (ITS) is described which stresses the importance of providing the user with knowledge about a given problem-domain before problem solving skills are put to the test. Central to this approach is the condition that knowledge about a given problem-domain can be 'decomposed' according to some well-grounded principle. The result of this decomposition is a body of information that is organised according to semi-autonomous topics into a hierarchy of functionally related information structures.< >
The article reviews the experience gained in implementing intelligent courseware using two expert system building tools: SAPS and Crystal. SAPS offers assistance on the preparation and interpretation of the sources an...
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The article reviews the experience gained in implementing intelligent courseware using two expert system building tools: SAPS and Crystal. SAPS offers assistance on the preparation and interpretation of the sources and applications of funds statement (SAFS) which is attached to all published accounts. It also offers some aspects of the functionality of an expert system. Crystal is an expert system shell with strong procedural functionality and was used for knowledge base development.< >
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