Showing papers on "Electromagnetics published in 1989"

Advanced engineering electromagnetics

Abstract: Time--Varying and Time--Harmonic Electromagnetic Fields. Electrical Properties of Matter. Wave Equation and Its Solutions. Wave Propagation and Polarization. Reflection and Transmission. Auxiliary Vector Potentials, Contruction of Solutions, and Radiation and Scattering Equations. Electromagnetic Theorems and Principles. Rectangular Cross--Section Waveguides and Cavities. Circular Cross--Section Waveguides and Cavities. Spherical Transmission Lines and Cavities. Scattering. Integral Equations and the Moment Method. Geometrical Theory of Diffraction. Greena s Functions. Appendices. Index.

Actuators for micro robots

Abstract: The problem of scaling robot actuators down to microscopic scale is examined in a review. It is shown that several forces scale well into the micro domain. These include electrostatics, hydraulics, pneumatics, and biological forces. Electromagnetic forces have a less favorable scaling. The scaling of electrostatics and electromagnetics is explained, and two electrostatic actuators are presented. The first actuator is a harmonic electrostatic motor. This motor uses rolling surfaces that reduce friction, and has an integral gear reduction that increases the torque output of the motor. The second actuator is designed to move fibers into alignment with other fibers. >

The spectral domain method in electromagnetics

Abstract: Presents an introduction to spectral domain techniques and illustrates their application to a variety of electromagnetic boundary value problems. An integrated approach to the solution of seemingly diverse problems is presented in order to show the underlying unity of solution. Complex problems can

A new technique for numerical electromagnetics

Abstract: A new method for numerically solving electromagnetic boundary value problems has been independently developed by at least five groups worldwide [l-61. The unique feature of the technique is that the unknowns are analytic solutions of the field equations corresponding to sources that are some distance away from the surface where a boundary condition is being enforced. A generic name for the technique has not yet been generally accepted. Proposed names include "Extended Source Technique," "Generalized Source Technique," and "Generalized Multipole Technique," with the latter being favored by most of the workers using the method. It is hoped that a special session can be arranged for this technique at the next AP meeting in San Jose, and anyone working on this type of solution is invited to submit a paper to the AP session.

Cerebral and Carotid Haemodynamic Changes Following Cervical Spinal Cord Stimulation. An Experimental Study

Abstract: Since it is accepted that spinal cord stimulation may produce segmentary vasodilation, it is presumable that when applied in the high cervical segments some carotid and cerebral blood flow changes can be expected. Following this assumption, 25 dogs and 25 goats were used. Under routine experimental conditions a C 7 laminectomy was performed in these animals and a bipolar lead introduced and manipulated in the epidural space till the right C 2 segment. Right common and internal carotid arteries of the dogs were isolated and electromagnetics probes placed for continuous monitoring of blood flow changes. Right internal maxillary artery was isolated and its branches ligated for flowmetry of hemispheric blood flow in the goat. 131I antipyrine also studied to control regional cerebral blood flow changes. Arterial pressure and blood gasometry were periodically determined to avoid masking results. Pulse width of 0.1 to 0.2 msec, 80 to 120 cps and amplitude to muscle contraction threshold at low rate were used as electrical parameters. After stimulation common and internal carotid blood flow increased with a mean of 60% and hemispheric blood flow with a mean of 55% according to flowmetry findings. Iodoantipyrine studies showed an average increase of 35%. These changes were not modified by atropine, morphine and naloxone and partially blocked by indomethacin, Cimetidine and propanolol.

Electromagnetic remote sensing. Low frequency electromagnetics

Abstract: : A series of lectures are presented on the topic of the location and identification of compact objects by low frequency electromagnetics. These lectures were presented as a portion of two graduate level courses in electrical engineering at the University of Toronto in 1985 and 1987. magnetostatics, electrostatics and electromagnetic induction techniques are discussed in detail. Keywords: Magnetic, Canada, Remote sensing, Detectors, Magnetostatics, Electromagnetic detectors, Electromagnetic induction, Electrostatics, Compact, Object, Detection, Location, Identification, Quasiremote, Remote sensing.

Direct and efficient solutions of integral equations for scattering from strips and slots

Abstract: Singular integral or integro‐differential equations (SIE or SIDE) are often used for the analytical formulation of two‐dimensional boundary‐value problems. The methods for solving them depend primarily on the complexity of their kernel and on the kind (first or second) of the SIE itself. First‐kind SIEs with a Laplacian kernel are characteristic in electrostatics. A successful method for solving them is a regularization approach based on the transformation of the SIE to an equivalent Fredholm regular integral equation of the second kind. Well‐known inversion formulas are essential to this approach. In electromagnetics, a Hankel‐type kernel complicates matters considerably; inversion formulas and regularization techniques end up as cumbersome indirect procedures making necessary the recourse to a more direct method. Such a method is developed in this paper in combination with a very suitable expansion of the Bessel function, that multiplies the logarithmic singularity of the Hankel kernel, into a series of Chebyshev polynomials of the first or second kind. It is essentially a direct analytical approach that requires fewer expansion functions per wavelength than the method of moments and whose matrix elements are not numerical integrals of singular functions, but quite concise and rapidly convergent series expansions. The efficiency of the method is shown by applying it to scattering of E‐polarized waves from a strip conductor right on the interface between two different dielectric half‐spaces and of E‐ or H‐polarized waves from a slot in the presence of a uniaxially gyrotropic half‐space. Asymptotic expressions for the far‐scattered field are given in all these cases and numerical results are plotted and compared with existing similar ones in certain special situations.

Dynamic modeling of an induction motor connected to an adjustable speed drive

Abstract: A method that treats electromagnetics, circuits, and mechanical dynamics as a coupled set of equations is described. The finite-element method is used along with a numerical integration method for time stepping, and the Newton-Raphson scheme is used to model saturation. Moving parts are described in terms of a moving, deformable finite-element mesh. A 9000 HP squirrel cage induction motor is used as an example of the application of the method. >

Palmietfontein kimberlite pipe, South Africa—A case history

Abstract: The Palmietfontein kimberlite pipe is located 150 km northwest of Johannesburg, South Africa. It was emplaced at the contact between mafic rocks of the Bushveld complex and syenites of the Pilanesberg complex, and coincides with the intersection of two major faults. Palmietfontein is one of the larger known kimberlite pipes in South Africa; it has a surface area of 12 ha and is diamondiferous. The present geophysical study was designed to assist in planning an extensive program of trenching and drilling. Unweathered kimberlite has geophysical responses very similar to the country rock at Palmietfontein. Weathering and alteration of the upper 50 m of the pipe, however, have resulted in various physical changes, which has made the target amenable to investigation by various geophysical techniques. The surveys used in this study are gravity, electrical, seismic refraction, and airborne and ground magnetics and electromagnetics (EM). The boundary of the pipe was accurately defined, and the dip of the wallrock...

Proceedings of the Fifth International Symposium on Numerical Methods in Engineering

Abstract: Contents: Volume 1: Foreword.- Invited papers.- Minisymposia.- Oral presentations: Solid mechanics.- Fluid mechanics.- Volume 2: Foreword.- Combustion and thermal analysis.- Electromagnetics.- Finite element methods.- Numerical analysis and software.- Vector and parallel computing.- Solid mechanics.- Fluid mechanics.- Thermal problems.- Finite element methods.- Software.

From "reaction concept" to "conjugate gradient": have we made any progress

Abstract: The objective of this paper is to trace the roots of development of various numerical techniques used in electromagnetics. The rates of convergence of each of the techniques is also outlined. Finally, we present the differences among the techniques from a purely numerical standpoint.

Engineering Design for Electrical Engineers

Abstract: I. PRINCIPLES. 1. Engineering Design. 2. Project Implementation. 3. Design Guidelines and Implementation. 4. Project Communication. II. PRACTICE. 5. Digital Module. 6. Analog Module. 7. Electromagnetics Module. 8. Feedback Control Module. 9. Communications Module. 10. Power Module.

Numerical techniques for microwave and millimeter- wave passive structures, edited by Tatsuo Itoh [Book review]

Abstract: As newly-ap ointed AP-S Chapter Activity Chairman, I would li k“ e to thank our past Chairman, Jay Schindler, for his outstanding contributions in supporting all the Chapters. In the last several years, we have experienced growing interest in Chapter activities, as evident from our last year’s activity reports. It is our belief that local Chapters are capable of improving and increasing interest and interaction among the AP-S members. This is primarily achieved by organizing regular meetin s and inviting outstanding speakers, who address techcal areas of current interest to the local members. As a new Chairman, I would like to assist Chapters as much as possible, and I hope that we will be able to effectively serve our members. There are different types of Chapter activities which are available for each Chapter, based on its needs. It is the Chapter officers’ responsibility to bring their Chapter’s needs to my attention. As it was explained in our Chapter officers’ meeting in San Jose, Chapters who request financial support must justify their requests carefully and properly.

Comments about time domain techniques in electromagnetics

Abstract: Nowadays, electromagnetic wave propagation and scattering are studied directly in the time-domain, whereas previously one consldered sine-wave excitations and Fourier transformations into the frequencydomain. Time-domain approaches are certainly much closer to the physical reality, but how do they deal with propagation within (or with scattering from) material media, since material properties are dispersive (frequency-dependant), at least over parts of the frequency spectrum? It is not obvious that timedomain approaches can determine the resulting distortion of the signal.

DTRC laboratory electromagnetic accelerator system design, modeling and simulation

Abstract: The authors describe the development of an analytical model which was used to simulate and aid in the design of a coaxial accelerator. The model is based on a variable set of differential equations that represent the electromagnetics of the system coupled with the mechanical equations of motion. It is concluded that this approach in modeling results in excellent accuracy, is numerically efficient and stable, and can be run on a desk top computer. The resultant design was used to build a full-scale laboratory model which was instrumented and tested. Some results from the actual device are included for comparison with the simulation results. >

Magical microwaves: the exploitation of the century

Abstract: The celebrated discoveries of Maxwell, Hertz and many others heralded a century rich in the exploitation of ideas to create electronic systems beneficial to mankind. This address focuses on the recent exploitation of electromagnetics concerning the sensing of images, generation of force and dispensing of heat thus highlighting important trends in the kindred RF and microwave industries. A recapitulation of the milestones in the advances over the century emphasises the interdependence of theory, material development and system innovation. Today's CAD/CAM and chip-integration philosophies have taken the batch-oriented microwave component industry to the threshold of mass production. Improving both the accuracy of electromagnetic design equations and the manufacturing technology are critical issues, and the revolutionary antenna phased array technology well illustrates these challenges. The diverse advances in passive and active image sensing systems rely heavily on signal processing, and examples include the radiometric sensing of temperature and microwave diffraction tomography in medical diagnostics, and the synthetic aperture radar scanning of the earth. A complementary topic concerns the disguise of radar target signatures, mainly in defence, and the use of ingenious electromagnetic wave scattering behaviour. Equally daunting is the invention of microwave sources with astronomical power levels that make defensive electromagnetic beam weapons a possibility, and fascinating experiments on electromagnetic rocket launchers and guns for space scenarios have been reported. Finally commonplace microwave domestic cooking is seen to be but one of a multitude of applications including pest control, seed germination and cancer therapy. Skill shortages, achieving the potential of CAD in mass production, and exploiting the emerging technologies, are some of the stimulating challenges ahead.

Advanced engineering electromagnetics, by Constantine A. Balanis [Book review]

Abstract: This volume is a welcome additin to the collection of texts available for adoption in graduate electromagnetic theory courses. Given its length, collection of topics, and readability, it is clearly appropriate for a two-semester course in advanced electromagnetic theory. It also will find considered use as a reference text

Applications of model-based parameter estimation in electromagnetic computations

Abstract: A widely used computer model in electromagnetics is the method of moments (MM) whereby an integral equation is discretized and approximated as a matrix whose solution yields a sampled representation of the physical problem of interest. The computer time T required to evaluate a MM model at a single frequency depends on the number of unknowns or equations N as T approximately AN/sup 2/+BN/sup 3/, where A and B are computer- and algorithm-dependent constants. Many frequency samples F may be required to establish a response over a prescribed frequency range, leading to a computer time proportional to TF. One way of reducing this time is by minimizing the number of frequencies at which the MM calculation must be done, i.e. by reducing F using prior knowledge of the expected frequency behavior in the form of a model, a pole series, for example. Another is to reduce T, which for some problems is dominated by the matrix fill time, or the A term. Both possibilities are candidates for model-based parameter estimation (MBPE) as demonstrated here, the first using a predetermined, pole-series model and latter a multinomial, self-organizing model. >

An optimum finite element grid generator for triangulating rotating and fixed objects in electromagnetics

Abstract: A description of an automatic two-dimensional finite-element grid generator which greatly assists in improving preprocessing operations and geometry handling for electromagnetic field computations is presented. The algorithm developed iteratively triangulates a set of points, defining a field region, into optimal finite-element meshes. The proposed mesh generator uses an approach proven to be user-friendly and efficient, especially in analysis of medical devices. This is because instead of using node-insertion techniques, as employed in most grid generators, the user gives dimensions and characteristics of each subregion in the large region to be analyzed. Furthermore, it is possible to add, delete, or modify a region configuration and grid without gross efforts. The triangulation and mesh refinements are performed automatically by the software without user intervention. The mathematical procedure used in developing the algorithm is based on the concept of Delauney triangulation. Variational principles are used to solve the electromagnetic field problem. Several examples are presented to show the effectiveness of this grid generator in handling a variety of problems and geometrical configurations. >

WEMAP-a computer aided instructional tool for electromagnetics

Abstract: WEMAP is an electromagnetic analysis computer code for teaching electromagnetics to power engineering students. WEMAP is a stand-alone interactive graphics system for electromagnetic analysis, which includes electrostatics, magnetostatics, eddy currents (time harmonic as well as transient), and permanent magnet fields. These capabilities are described, and examples are given to illustrate how this program can enhance the classroom presentation of some of the electromagnetic phenomena. >

Numerical modeling of monopoles on radial-wire ground screens

Abstract: The monopole antenna on a radial-wire ground screen has been particularly resistant to numerical modeling due to the difficulty of treating the effect of the air-ground interface and the large total electrical length of wire involved. A moment-method code capable of modeling ground screens and other antennas near to or buried in the ground was developed in the code NEC-3 (numerical electromagnetics code-3). A version of NEC-3 known as NEC-GS was then specialized to model vertical monopoles or uniform radial-wire ground screens, taking maximum advantage of the symmetry of the screens and their currents. Some results of this code are presented to compare the performance of ground screens of varying dimensions and configurations, and to determine optimum design parameters. >

Decomposition Of The Moment Method Impedance Matrix Into Quasi-Static And Residual Components

Abstract: Since 1968 when Harrington first introduced the use of the moment method in electromagnetics [1,2], the coefficient of the unknown currents has been characterized as an "impedance" matrix. Since then a large body of work has appeared in the literature extending and refining this technique. Recent efforts to discover faster ways of filling the impedance matrix in MININEC [3,6] have resulted in a new interpretation of the impedance matrix. By extending the concept of separating the Green's function into singular and nonsingular parts to an additive decomposition of the impedance matrix, three matrices are defined: a static elastance matrix which alone determines the static charge; a static inductance matrix which, combined with the elastance matrix determines reactive behavior below resonance; and a residual frequency dependent matrix. Using the quasi-static solution and a first-order approximation for the residual mat.rix, an equivalent circuit valid up to about one-half of the resonant frequency was obtained.

Parallel computation of electromagnetic scattering from arbitrary structures

Abstract: The method of moments is used to solve functional equations arising in electromagnetics. A specific area, scattering from conducting structures, is treated by developing techniques for reducing the CPU time using concurrent and vector processing. A noniterative and an iterative technique are used to solve the matrix equation. The algorithm developed was run on an Alliant FX180 parallel computer. >