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Physical Science, Measurement and Instrumentation, Management and Education - Reviews, IEE Proceedings A

Issue 8 • Date Nov 1988

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Displaying Results 1 - 15 of 15
  • Research co-operatives: experiences with a small-scale approach

    Page(s): 539 - 540
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    Small research groups, jointly sponsored by several industrial companies, have been used to address common technological problems at the precompetitive stage. The authors discuss experiences in forming and operating the groups. View full abstract»

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  • Whitney forms: a class of finite elements for three-dimensional computations in electromagnetism

    Page(s): 493 - 500
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (911 KB)  

    It has been recognised that numerical computations of magnetic fields by the finite-element method may require new types of elements, whose degrees of freedom are not field values at mesh nodes, but other field-related quantities like e.g. circulations along edges of the mesh. A rationale for the use of these special `mixed¿¿ elements can be obtained if one cxpresses basic equations in terms of differential forms, instead of vector fields. The paper gives an elementary introduction to this point of view, presents Whitney forms (the mixed finite elements alluded to), and sketches two numerical methods (dual, in some sense), for eddy-current studies, based on these elements. View full abstract»

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  • Comparison of different boundary integral formulations when coupled with finite elements in three dimensions

    Page(s): 501 - 507
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (822 KB)  

    Several boundary integral formulations are described and compared for calculating the `outside stiffness matrix¿¿ for a hybrid finite-element boundary-integral method in three-dimensional (3D) electromagnetic modelling. The methods of single-layer sources and of Green's identity, as well as the Trefftz method, have been analysed when using, respectively, collocation and variational techniques for the numerical discretisation. The analysis shows that results obtained by both of the Green's identity and the single-layer methods are similar, and that the Trefftz method can be seen as a special case of the latter method. In other respects, as the single-layer method is more convenient in exterior field calculation, it has been adopted by the authors. The choice of the source distribution and the treatment of singularities by using a semi-analytical technique or by locating the virtual sources separated from the boundary are also discussed. The different methods have been numerically implemented in the `Trifou¿¿ (3D eddy-current computation) code. Calculations for a test example, concerning eddy currents in a hollow sphere, have been completed. The obtained results have been compared and the corresponding conclusions are given at the end of the paper. View full abstract»

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  • `Local¿ conditioning of broad-area vacuum-insulated high-voltage electrodes

    Page(s): 508 - 514
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (905 KB)  

    A new in situ `local¿ conditioning technique is described for improving the hold-off capability of a high-voltage vacuum gap. This involves spatially locating individual prebreakdown electron emission sites and then selectively eliminating them by some form of `zapping¿ probe. Three types of probe have been evaluated, namely focused ion and electron beams, and needle spark knocking. For OFHC copper electrodes, the ion-beam probe was consistently the most effective, routinely giving an improvement of 200% in the insulating capability of the gap. As a control, the performance of this `local¿ conditioning technique is compared with the conventional glow-discharge and gas-sputtering `total-electrode¿ conditioning techniques. View full abstract»

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  • Computation of fields due to current sources

    Page(s): 515 - 522
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    In finite-element codes where the magnetic field is split into a reduced magnetic intensity and the gradient of a scalar field, the computational effort spent in calculating the field due to impressed currents can be great. This contribution seeks to show that there are an infinite number of ways of calculating the field due to these currents, and that a proper choice can greatly increase the computational efficiency of the finite-element method. View full abstract»

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  • Electromagnetism and semantics

    Page(s): 523 - 527
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (795 KB)  

    The terminology still in common use by many writers on electromagnetic topics is unconsciously related to the original Maxwell ether model, which gives the E, D, B and H vectors equal status as a set of four fundamental field quantities. Maxwell's equations are usually presented in terms of all four quantities, together with the `constitutive relationships of the medium¿¿: This is an unnecessarily complicated and physically unrealistic approach, which is a source of much confusion both in students and in practising engineers. Observation demonstrates that only three axioms underlie classical electromagnetism: the invariance of electric charge, Coulomb's law, and the constancy of the velocity of light. These axioms lead to Maxwell's equations via special relativity and the Lorentz transformation; i.e. without any necessity for an ether concept. Further consideration of the physical implications leads to a strong recommendation that the continued use of semantically misleading terminology, such as `magnetic field strength H¿¿ or `the permittivity of free space¿¿, should be discouraged. A tentative glossary of acceptable terminology is put forward for consideration by teachers and by authors. View full abstract»

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  • Book review: Business for Engineers

    Save to Project icon | PDF file iconPDF (174 KB)  
    Freely Available from IEEE
  • Knowledge-based project control employing heuristic optimisation

    Page(s): 529 - 538
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1292 KB)  

    One particular problem of great commercial significance which professional project engineers confront is that of expeditious control of resources to achieve timely completion of complex plans. A wealth of expertise exists, little if any of which has been formalised, so as to permit the development of computer-based aids for intelligent project control. The paper describes a heuristic algorithm which has been developed in close consultation with expert project engineers. It has been integrated within an intelligent knowledge-based system (IKBS) and the resultant computer tool evaluated in a real-world project management situation. The algorithm incorporates six variables which have been carefully formulated to assess the merit of expediting selected activities in project plans within a hierarchical framework of control strategies. An empirical study of these heuristics, taken in conjunction with the IKBS, is presented, and some parallels are drawn with an expert project engineeer's performance on a typical project plan. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Research co-operatives: experiences with a small-scale approach

    Page(s): 539 - 540
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (310 KB)  

    Small research groups, jointly sponsored by several industrial companies, have been used to address common technological problems at the precompetitive stage. The paper discusses experiences in forming and operating the groups View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Whitney forms: a class of finite elements for three-dimensional computations in electromagnetism

    Page(s): 493 - 500
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (620 KB)  

    It has been recognised that numerical computations of magnetic fields by the finite-element method may require new types of elements, whose degrees of freedom are not field values at mesh nodes, but other field-related quantities like, e.g. circulations along edges of the mesh. A rationale for the use of these special `mixed' elements can be obtained if one expresses basic equations in terms of differential forms, instead of vector fields. The authors gives an elementary introduction to this point of view, presents Whitney forms (the mixed finite elements alluded to), and sketches two numerical methods (dual, in some sense), for eddy-current studies, based on these elements View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • `Local' conditioning of broad-area vacuum-insulated high-voltage electrodes

    Page(s): 508 - 514
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (516 KB)  

    A new in situ `local' conditioning technique is described for improving the hold-off capability of a high-voltage vacuum gap. This involves spatially locating individual prebreakdown electron emission sites and then selectively eliminating them by some form of `zapping' probe. Three types of probe have been evaluated, namely focused ion and electron beams, and needle spark knocking. For OFHC copper electrodes, the ion-beam probe was consistently the most effective, routinely giving an improvement of 200% in the insulating capability of the gap. As a control, the performance of this `local' conditioning technique is compared with the conventional glow-discharge and gas-sputtering `total-electrode' conditioning techniques View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Knowledge-based project control employing heuristic optimisation

    Page(s): 529 - 538
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (904 KB)  

    One particular problem of great commercial significance which professional project engineers confront is that of expeditious control of resources to achieve timely completion of complex plans. A wealth of expertise exists, little if any of which has been formalised, so as to permit the development of computer-based aids for intelligent project control. The authors describe a heuristic algorithm which has been developed in close consultation with expert project engineers. It has been integrated within an intelligent knowledge-based system (IKBS) and the resultant computer tool evaluated in a real-world project management situation. The algorithm incorporates six variables which have been carefully formulated to assess the merit of expediting selected activities in project plans within a hierarchical framework of control strategies. An empirical study of these heuristics, taken in conjunction with the IKBS, is presented, and some parallels are drawn with an expert project engineer's performance on a typical project plan View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Comparison of different boundary integral formulations when coupled with finite elements in three dimensions

    Page(s): 501 - 507
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (564 KB)  

    Several boundary integral formulations are described and compared for calculating the `outside stiffness matrix' for a hybrid finite-element boundary-integral method in three-dimensional (3D) electromagnetic modelling. The methods of single-layer sources and of Green's identity, as well as the Trefftz method, have been analysed when using, respectively, collocation and variational techniques for the numerical discretisation. The analysis shows that results obtained by both of the Green's identity and the single-layer methods are similar, and that the Trefftz method can be seen as a special case of the latter method. In other respects, as the single-layer method is more convenient in exterior field calculation, it has been adopted by the authors. The choice of the source distribution and the treatment of singularities by using a semi-analytical technique or by locating the virtual sources separated from the boundary are also discussed. The different methods have been numerically implemented in the `Trifou' (3D eddy-current computation) code. Calculations for a test example, concerning eddy currents in a hollow sphere, have been completed View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Electromagnetism and semantics

    Page(s): 523 - 527
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (552 KB)  

    The terminology still in common use by many writers on electromagnetic topics is unconsciously related to the original Maxwell ether model, which gives the E, D, B and H vectors equal status as a set of four fundamental field quantities. Maxwell's equations are usually presented in terms of all four quantities, together with the `constitutive relationships of the medium'. This is an unnecessarily complicated and physically unrealistic approach, which is a source of much confusion both in students and in practising engineers. Observation demonstrates that only three axioms underlie classical electromagnetism: the invariance of electric charge, Coulomb's law, and the constancy of the velocity of light. These axioms lead to Maxwell's equations via special relativity and the Lorentz transformation; i.e. without any necessity for an ether concept. Further consideration of the physical implications leads to a strong recommendation that the continued use of semantically misleading terminology, such as `magnetic field strength H' or `the permittivity of free space', should be discouraged. A tentative glossary of acceptable terminology is put forward for consideration by teachers and by authors View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Computation of fields due to current sources

    Page(s): 515 - 522
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (380 KB)  

    In finite-element codes where the magnetic field is split into a reduced magnetic intensity and the gradient of a scalar field, the computational effort spent in calculating the field due to impressed currents can be great. This contribution seeks to show that there are an infinite number of ways of calculating the field due to these currents, and that a proper choice can greatly increase the computational efficiency of the finite-element method View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.