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Radio and Electronic Engineer

Issue 11.12 • Date November-December 1980

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Displaying Results 1 - 12 of 12
  • Remote sensing of the environment

    Page(s): 531 - 532
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    Freely Available from IEEE
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  • Engineering and education

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    Freely Available from IEEE
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  • Systems Engineering: an approach to whole-system design

    Page(s): 545 - 558
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1715 KB)  

    Since World War II the magnitude and complexity of technological enterprise has increased dramatically. So too have the costs of development, mistakes and failures. The old-style project engineer who could often be his own designer and project manager has been replaced by a team¿the systems engineering staff¿who integrate, co-ordinate and evaluate the realization of a project through all its evolutionary phases. In particular, systems engineering has produced an approach to design and project appraisal that integrates and balances the various technical, economic, reliability, safety, logistic, support criteria oriented towards future market and operational requirements evaluated over the whole-life of the system. This introductory paper provides an entry to the systems concepts that underlie systems engineering, and then illuminates the practice through the perspectives of systems organization, design and planning. View full abstract»

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  • Oblique h.f. radiowave propagation in the main trough region of the ionosphere

    Page(s): 559 - 566
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    The propagation of 7.335 MHz, c.w. signals over a 5212 km sub-auroral, west-east path is studied. Measurements and semi-empirical predictions are made of the amplitude distributions and Doppler shifts of the received signals. The observed amplitude distribution is fitted with one produced by a numerical fading model, yielding the power losses suffered by the signals during propagation via the predominating modes. The signals are found to suffer exceptionally low losses at certain local times under geomagnetically quiet conditions. The mid-latitude trough in the F2 peak ionization density is predicted by a statistical model to be at the latitudes of this path at these times and at low Kpvalues. A sharp cut-off in low-power losses at a mean Kpof 2.75 strongly implicates the trough in the propagation of these signals. The Doppler shifts observed at these times cannot be explained by a simple ray-tracing model. It is shown however, that a simple extension of this model to allow for the trough can reproduce the form of the observed diurnal variation. View full abstract»

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  • Monitoring of various atmospheric constituents using a c.w. chemical hydrogen/deuterium laser and a pulsed carbon dioxide laser

    Page(s): 567 - 574
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    Applications of a c.w. chemical hydrogen/deuterium fluoride laser and a pulsed TEA CO2laser for monitoring of atmospheric trace constituents and process control are reported. The c.w. HF/DF laser has been used for field measurements of the HF concentration in the exhaust of an aluminium plant. The laser has also been operated as a DF laser for measurements of the HDO concentration in natural water samples. In addition, using a pulsed TEA CO2 laser in connection with the differential absorption technique, range-resolved ambient air measurements of the water vapour distribution in the vicinity of a cooling tower as well as measurements of the ethylene concentration over the area of a refinery have been performed. The results have been further evaluated using simple and reasonable propagation models. From this both the diffusion parameters and the total mass emission of a source could be obtained. View full abstract»

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  • Computer processing of multi-layer imagery data

    Page(s): 575 - 584
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    The technique and methodology of computer-aided image processing has become a valuable tool for handling, processing and analysing multi-spectral imagery data acquired from sensors in aircraft and satellites. This paper describes some of the background and the rationale for performing computer processing and also discusses types and kinds of operations which come into use. The main purpose of the paper is to give a description of a software system for performing various tasks in computer-aided image processing. One interesting part of this system is a supervised classification program system for pixelwise (or objectwise) multi-layer classification. The classification algorithm performs class assignment in a linearly transformed space. It is a classifier whose c.p.u. time is approximately linearly dependent upon the number of layers (e.g. spectral features) compared with an approximate quadratic dependence for a classical implementation of the maximum-likelihood Bayes classifier for normally-distributed features. Examples of pilot and application studies of various problems in environmental monitoring and land use are also given. Forest monitoring is considered to be an important application in Sweden. The paper also shows the importance of incorporating non-spectral topographic) data for increased classification accuracy of detecting clear-cut areas. View full abstract»

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  • Some aspects of the construction and use of atmospheric acoustic sounders

    Page(s): 585 - 597
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    Acoustic sounder design and performance parameters are described. Various atmospheric features as recorded by the acoustic sounder, including thermal plumes, inversions and waves, are presented and their interpretation given. The use of the acoustic sounder to monitor the height of low level layer cloud and the depth of radiation fog is discussed as well as the detection and tracking of plumes of methane gas. View full abstract»

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  • Quantitative interpretation of acoustic echoes from the planetary boundary layer

    Page(s): 598 - 610
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    Recent advances in the quantitative application of acoustic sounders to studies of the atmospheric boundary layer are described. Precise measurement of the echo strength is shown to provide a means of estimating the structure parameters for wind velocity and temperature. Extraction of the Doppler shift provides a method for obtaining information on the mean airflow and small-scale fluctuations in wind velocity View full abstract»

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  • Remote sensing of the sea-surface by dekametric radar

    Page(s): 611 - 623
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    The evolution of the technique of remote sensing of the sea-surface by dekametric radar is traced from the original observation of the Bragg resonant scattering phenomenon by D. D. Crombie in 1955 to its present applications to the measurement of surface wind-direction and wind-speed, wave-height spectrum, wave-directional spectrum and surface-currents. The central role played by the Doppler spectrum of the radar echoes is illustrated. The generation and spectral properties of wind-driven waves on the sea-surface are discussed including wave-wave interactions and the nature of electromagnetic scattering by first and second-order processes is described. An account is given of the techniques used for UK experiments on ground-wave radar surveying the Celtic Sea from West Wales. Synthetic aperture experiments using a moving vehicle permitted the directional spectrum of the sea-surface to be determined. Sky-wave experiments from a radar in Southern England permitted comparisons with sea-state and surface winds measured in the Rockall Bank area of the North Atlantic by oceanographic vessels and buoys. Finally, work in progress in the US and UK on improved narrow beam and interferometer radars and new methods for inversion of measured Doppler spectra to yield seawave spectra are reviewed. View full abstract»

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  • The influence of the elasticity of magnetic tape on some parameters of magnetic recording

    Page(s): 624 - 630
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    A tape driven by an accurately running capstan between precisely aligned guides cannot be scanned exactly. Due to the elastic properties of the tape there are elastic displacements superposed on the nominal tape movement. These additional tape movements which are generated by tension disturbances or natural frequencies may affect the recording and the playback. This effect is considered and estimated View full abstract»

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