Bird, TS 1980, 'Asymptotic behaviour of TE11 mode coupling in circular apertures', Electronics Letters, vol. 16, no. 14, pp. 529-530.
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An asymptotic formula for mode coupling in a finite planar array of circular apertures, which was derived previously, is compared with the exact solution for the case of TE11 mode coupling in two circular waveguides. It is shown that for dominant mode operation of a circular waveguide the asymptotic formula is accurate enough for most practical purposes, even for aperture spacings of the order of a wavelength. © 1980, The Institution of Electrical Engineers. All rights reserved.
Bird, TS & Boomars, JL 1980, 'EVALUATION OF FOCAL FIELDS AND RADIATION CHARACTERISTICS OF A DUAL-OFFSET REFLECTOR ANTENNA.', IEE Proceedings H: Microwaves Optics and Antennas, vol. 127, no. 4, pp. 209-218.
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A receive-mode analysis of a dual-offset reflector antenna consisting of an offset paraboloid and an offset hyperboloid is presented. In this analysis the field scattered from the offset paraboloid is determined using a g. t. d. formulation involving two edge points and a reflection point, if one exists. A method is described for deciding whether there is a reflection point from the gradient of the path length at the edge points. The focal-region fields and the radiation characteristics are computed by numerical integration of the physical optics current on the offset hyperboloid. An experimental antenna operating at 35 GHz is described. Results of measurements of radiation patterns and of the power coupled into a circular waveguide array feed are compared with theory. In each case reasonable agreement is achieved for copolarized directed components. However, the experimental antenna produced higher crosspolarization than expected.
Clark, BE & Shannon, AG 1980, 'A module in mathematics: Description and evaluation', International Journal of Mathematical Education in Science and Technology, vol. 11, no. 1, pp. 133-141.
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This paper describes an approach to the problem of teaching first year tertiary level mathematics students who have widely varying levels of achievement and ability in mathematics. The evaluation of some aspects of the proposed solution to the problem is based on a semantic differential and a Likert-type questionnaire. © Taylor & Francis Group, LLC.
Dovey, KA 1980, 'Politics and Guidance: An Overview of the South African School Guidance Service', British Journal of Guidance & Counselling, vol. 8, no. 1, pp. 1-10.
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The South African guidance service is an example of the way in which the population can be manipulated when a guidance service is used to serve the political and economic ends of a ruling group. The South African government views the guidance service as an ‘auxiliary education service’, the function of which is to ensure conformity to the official Christian National Education policy for White schools. ‘Pedagogy’ provides a theoretical explanation for deviance from Christian National norms, and thus is emphasised in the training of guidance personnel. The focus of the guidance service is upon the identification and reorientation of children who are ‘different’. The overview presented here provides an example of the consequences of unquestioning compliance of a guidance service with the values and norms of the dominant culture. It is argued that all guidance services constantly need to make explicit, and to question, the cultural assumptions upon which they operate. © 1980, American Industrial Hygiene Association. All rights reserved.
Goodwin, GC, Doan, HB & Cantoni, A 1980, 'Application of ARMA models to automatic channel equalization', Information Sciences, vol. 22, no. 2, pp. 107-129.
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This paper describes a novel approach to automatic channel equalization in digital transmission systems. The approach is based on the use of a finite-dimensional rational approximation to the channel characteristics. This class of channel approximation has the following advantages: it allows a finite parametrization of the channel impulse response which may be of infinite duration, it allows for the possibility of the noise being colored, it applies to either single- or multiple-channel systems, and it has the pedigogical advantage that many other algorithms in current use are based on models which are special cases of this model. The rational approximation to the channel characteristics is used in the paper to develop a new receiver structure using fixed-lag smoothing ideas. Simulation studies are presented showing that the receiver offers advantages over other algorithms for mitigating the effects of intersymbol and interchannel interference including those arising from carrier phase errors. © 1980 Elsevier North Holland, Inc. All rights reserved.
Heiman, JL, Bakoss, SL, Burfitt, AJ & Cridland, L 1980, 'MEASURED AND PREDICTED AXIAL STRAINS AND DEFORMATIONS IN A COLUMN OF A TALL REINFORCED CONCRETE BUILDING.', Institution of Engineers, Australia, Civil Engineering Transactions, vol. CE22, no. 3, pp. 193-201.
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A site investigation was carried out to determine the axial deformations of a column in a tall reinforced concrete building. Strains were measured in the column concrete using vibrating wire gages and the column deformations were measured by precise leveling. In addition to strain measurements on standard laboratory shrinkage and creep specimens, strain data were obtained from tests that related more closely to the site conditions. Appreciable differences occurred between shrinkage and creep strains measured in the laboratory and some of those obtained by methods given in codes. Shortcomings were found in some of the equations used to predict long-term creep strains from laboratory data and a hyperbolic equation was developed that enabled more accurate predictions to be made. Measured strains in the column were compared with predicted values obtained by two calculation methods and good agreement was obtained.
Kumar, A & Waldron, KJ 1980, 'DEXTROUS WORKSPACE.', American Society of Mechanical Engineers (Paper), no. 80 -DET-108.
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The concept of a dextrous workspace, the space in which a manipulator hand can reach any point and rotate fully about any axis through that pont, is introduced. It is shown that the extrous workspace is bounded by surfaces generated by the algorithm presented in another paper. It is also demonstrated that classes of manipulator geometries possessing dextrous workspaces do exist.
Kumar, A & Waldron, KJ 1980, 'WORKSPACES OF A MECHANICAL MANIPULATOR.', American Society of Mechanical Engineers (Paper), no. 80 -DET-107.
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A new theory and a resulting algorithm for tracing the bounding surfaces of mechanical manipulator workspaces is presented. The natures of the numerous singular configurations and means of accommodating them within the algorithm are also studied. In order to sort surfaces of interest from the large number of possible solutions, a numerically implementable labelling technique is also presented. The algorithm is applicable to all practicable manipulator configurations with three, or more, degrees of freedom.
Loganathan, P & Balakrishnamurti, TS 1980, 'Effects of NPK fertilizers on young coconut (cocos nucifera) on a sandy soil in Sri Lanka', Experimental Agriculture, vol. 16, no. 1, pp. 41-48.
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In a 4 × 4 × 4 NPK field experiment with coconut on a sandy soil, N increased girth, height and leaf production during the pre-bearing period, but phosphorus (up to 6½ years) and K (up to 3½ years) had no effect on any vegetative growth parameters. The rates of fertilizers for optimum copra and nut yield (13 to 16 years) were 0.35, 0.73 and 0.64 kg N, PO and KO/palm/ year respectively. The high P requirement was due to the low solubility of the saphos phosphate in these sandy soils. A positive N × P interaction was also observed. © 1980, Cambridge University Press. All rights reserved.
Loganathan, P & Fernando, WT 1980, 'Phosphorus sorption by some coconut‐growing acid soils of Sri Lanka and its relationship to selected soil properties', Journal of the Science of Food and Agriculture, vol. 31, no. 7, pp. 709-717.
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Phosphorus (P) sorption in the presence of 10−2M calcium chloride by ten coconut‐growing acid soil samples of Sri Lanka belonging to the Ultisol, Alfisol and Entisol orders was evaluated using the Langmuir sorption isotherm. The data for all samples fitted the single‐site Langmuir sorption isotherm when equilibrium P was less than 1 μg ml−1, but showed some deviations at larger concentrations of P. A two‐site Langmuir sorption isotherm was successfully used to describe the sorption data of three samples at these high concentrations. The single‐site Langmuir sorption maxima were greater for Ultisols (349–825 μg g−1) than for the other soils (136–345 μg g−1). These sorption maxima were significantly correlated with %‐clay, %‐silt, dithionite‐extractable iron, and 1M ammonium acetate (pH 4.8)‐extractable aluminium. Regression analysis of P sorption on different forms of iron (Fe) and aluminium (Al) indicated that crystalline ‘free Fe oxides’ (dithionite‐extractable Fe minus 0.3M oxalate‐extractable Fe) and ‘active Al’ which consists of hydroxy Al monomers and polymers [1M ammonium acetates, (pH 4.8)‐extractable Al minus 1M potassium chloride extractable Al] were the important factors contributing towards P sorption. Copyright © 1980 John Wiley & Sons, Ltd
PHUOC, HB & TANNER, RI 1980, 'THERMALLY-INDUCED EXTRUDATE SWELL', JOURNAL OF FLUID MECHANICS, vol. 98, no. MAY, pp. 253-271.
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