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Magnetics, IEEE Transactions on

Issue 3 • Date May 1982

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Displaying Results 1 - 25 of 27
  • [Front cover and table of contents]

    Page(s): 0
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    Freely Available from IEEE
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  • Some aspects of the present status of HGMS

    Page(s): 812 - 816
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    It is proposed that the magnetic force density can be regarded as the principal single parameter for the characterization of magnetic separation devices. A classification of the various devices is presented and the design features as well as the processing capabilities of both conventional and superconducting large-scale HGMS machines is discussed. Future developments of HGMS are also considered. View full abstract»

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  • A study of the mechanisms of particle buildup on single ferromagnetic wires and spheres

    Page(s): 817 - 821
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    Particle buildup processes for paramagnetic, diamagnetic and ferromagnetic particles in HGMS are reviewed, and new data are presented. Previously published data are discussed using the local flow velocity in the vicinity of a collection wire instead of the average flow velocity. View full abstract»

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  • Evaluation of magnetic filter performance

    Page(s): 822 - 826
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    In recent years, in high gradient magnetic separation, two mainstream lines of basic investigation have evolved. The first of these has involved theoretical and experimental research on the basic mechanisms of particle build-up on individual fibres. The second deals with the overall performance of filters comprising random matrices in high magnetic fields and, in particular, with the phenomenon of breakthrough. This paper attempts to correlate information from these two major lines of effort. View full abstract»

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  • Application of the theory of magnetic filtration in determining the optimum filter configuration

    Page(s): 827 - 832
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    The magnetic filter theory developed earlier Is applied in the determination of optimum filter dimensions. As an example a plan for a process for the purification of waste water from a hot rolling mill is discussed in detail. Estimates of the filtration costs as a function of filter size are given. View full abstract»

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  • The physics of high intensity dry magnetic separation

    Page(s): 833 - 835
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    A stream of particles, falling under gravity and influenced by air drag, is analysed under the influence of a transverse magnetic force. The magnetic particles are deflected and collide with other particles. Under reasonable approximations concerning the nature of the particles and the type of collisions, an average transverse magnetic velocity is derived, as well as a maximum stream width for complete separation, which may be as much as 0.6cm. This is then combined with the calculated throughput to obtain an optimised value, which may be as large as 6 tons/hour for a magnet of diameter 365mm. View full abstract»

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  • The use of magnetic techniques in the development of a hydrogenation process

    Page(s): 836 - 840
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    Finely divided Raney Nickel is widely used as a hydrogenation catalyst in the chemical industry and in the refining or hardening of oils and fats. Catalyst removal from process streams is usually carried out by filtration or by centrifugation. Catalyst recycle is difficult owing to the abrasive and pyrophoric nature of the catalyst, general solids handling problems and the propensity of the catalyst to form blockages in linework and in processing equipment. This paper describes the development of a novel design of reactor using magnetic techniques to overcome these problems. An electromagnetic coil is used at the end of a batch to induce sufficient magnetism within the Nickel particles suspended in the process liquor to cause flocculation or agglomeration of the catalyst particles into clusters. These agglomerates settle much faster than the original finely divided material and within minutes most of the catalyst settles out on the base of the vessel. The slight haze of catalyst which remains is removed using an external HGMS unit which is backflushed into the reactor by the following charge. Settled catalyst is easily resuspended by an agitator. Alternative ways of applying the magnetic flocculation technique are described and ways of improving the HGMS unit are discussed. View full abstract»

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  • A review of HGMS methods of coal cleaning

    Page(s): 841 - 846
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    High Gradient Magnetic Separation has been applied to the problem of cleaning coal in several ways. One is by direct mineral removal from coal slurried in water or oil. Similarly, attempts have been made to desulfurize dry coal. Coal liquids, or solvent refined coal, can have their sulfur and ash content reduced by the filtration or separation of undissolved well liberated minerals. The results of such efforts depend on the magnetic properties of the coal minerals. These have been studied and even altered to improve magnetic separation performance. HGMS has also been employed for indirect use in coal cleaning to recover heavy medium (magnetite) used in fine coal cleaning circuits. This paper is a review of our work on these applications and that of others over several years. View full abstract»

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  • High gradient magnetic separation of fly ash

    Page(s): 858 - 861
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    Preliminary experiments have been performed on the high gradient magnetic separation (HGMS) of three fly ash samples. The enrichment of trace elements has been studied in order to determine whether retrieval of raw materials and the removal of harmful elements which might otherwise be leached from the disposed fly ash are feasible. Results are analyzed in terms of the capture efficiency, the magnetization and the elemental composition of the magnetically separated fractions. In all samples the retrieval of iron was quite high, and for the Australian fly ash enrichment by at least a factor of 2 was observed for several trace elements. Explanations are offered for the differences in processing characteristics among the various fly ash samples, and suggestions are given for additional testing to confirm these theories. View full abstract»

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  • The influence of surface forces of magnetic separation

    Page(s): 862 - 865
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    Results of the experimental investigation of the influence of surface forces on high gradient magnetic separation of iron ores will be presented. Surface characteristics of the slurries of pure hematite and hematite ores ground below 100 μm and 40 μm were varied from pH = 1.5 to 11 and these test samples were treated in high gradient magnetic separator at magnetic fields from 0.1 T to 0.7 T. The experimental data indicate that the maximum of grade and recovery of magnetic fraction of the ore can be obtained at pH corresponding to the point of zero charge, while at other pH the grade and recovery decrease. Since pH of point of zero charge for iron oxide is different from pH corresponding to water used in iron dressing plant, adjustment of pH of the slurry could lead to a substantial increase in grade and recovery. These considerable variations of grade and recovery can be attributed to a higher probability of retention of the particles on the matrix, higher resistance of the deposited particles against the shear stress and to selective magnetic and ionic flocculation of magnetic or gangue particlec. View full abstract»

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  • Direct digital control of a superconducting magnet

    Page(s): 866 - 876
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    A microcomputer-based controller and its input/output interfaces have been developed for an inductor-converter unit (IC unit) which consists of a six-pulse Graetz-type converter and a solenoidal superconducting magnet (SM). The SM current is feedback-controlled through the following operations: detection of the SM current, comparison with the reference input for generation of the error signal, determination of the firing angle by the digital operation of compensation, and generation of the trigger pulses. The algorithms for digital compensation have been studied by experiments as well as computer simulations. Proportional-integral-derivative (PID), first-order exponential response with transport delay (Dahlin algorithm), and finite time settling control (FTSC) algorithms have been simulated and experimented by using the IC unit. Accurate agreements between the results of simulations and experiments have been obtained for the PID and Dahlin algorithms. The FTSC algorithm has shown the best response of the three methods. View full abstract»

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  • Selective microelectrodeposition of Ni-Fe patterns

    Page(s): 877 - 879
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    Ni-Fe patterns of reproducible high quality for integrated thin film heads can be made by selective microelectrodeposition. A Ni-Fe bath characterized by improved microthrowing and long bath operation time has been used for this technique. Precise replication of mask profile, uniformity of thickness and chemical composition, and favorable magnetic properties of the microstructures of varying size are significant features of the technique. View full abstract»

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  • Wall clusters and domain structure conversions

    Page(s): 880 - 887
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    The significance of wall clusters, which is a new concept in the theory of soft magnetic materials, is experimentally demonstrated in thin Permalloy configurations. The wall cluster is a collection of domain walls that have one intersection line in common. The transformation of the domain structures takes place through a coherent movement of the domain walls. The correlation between the walls is especially dominant at the intersection line of the walls, called the cluster knot. Relations for the mutual positions of the walls in the wall clusters of great practical relevance are derived explicitly and verified experimentally. The domain structure is formed by the concatenation of wall clusters. The clock sense of the rotation over the walls in the clusters determine which walls of two clusters are linked during the formation of the domain structure. The creation of new clusters takes place through the unfolding of the walls of the clusters which originally coincide with the so-called creation line. As is demonstrated fully, the application of these ideas improves the insight into the complex process of domain structure transformations. View full abstract»

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  • Third-order theory and bang-bang control of voice coil actuators

    Page(s): 888 - 892
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    A theory of voice coil motor actuators involving third-order differential terms in displacement that includes the inductance of the motor coil has been developed for bang-bang control time-optimal performance. Universal curves have been obtained using the theory that exhibits relationships between dimensionless quantities. The curves enable designers to choose appropriate actuator performance parameters to meet design objectives. Experimental methods have been described to determine some of the important parameters involved in the theory. View full abstract»

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  • Dependence of reproducing gap null on medium permeability and spacing

    Page(s): 893 - 897
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    Experimental evidence and theoretical calculations show that the position of the reproducing gap null is influenced by the anisotropic permeability of the recording medium and the head-to-medium separation. Results indicate a stronger influence than expected from previous theory. The shift is typically 4 percent for a mean relative permeability of two and minimal head separation. View full abstract»

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  • A model of anisotropic Alnico magnets for field computation

    Page(s): 898 - 904
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    The modeling of an anistropic Alnico magnet for the purpose of field computation involves assigning a value for the material's permeability in the transverse direction. This is generally based upon the preferred direction properties, being all that are easily available. By analyzing the rotation of intrinsic magnetization due to the self-demagnetizing field, it is shown that the common assumptions relating the transverse to the preferred direction are not accurate. Transverse magnetization characteristics are needed, and these are given for Alnico 5, 5-7, and 8 magnets, yielding appropriate permeability values. View full abstract»

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  • The influence of applied tensile stress on power loss in Co-rich amorphous Co-Fe-Si-B ribbons with induced magnetic anisotropy

    Page(s): 904 - 907
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    The influence on power loss PTof applied tensile stress σ in amorphous (Co0.89Fe0.11)72Mo3Si15B10(lambda_{s} > 0) and Co73Mo2Si15B10(lambda_{s} < 0) ribbons with different induced magnetic anisotropy Kuis reported. The losses are measured under sinusoidal flux conditions atf = 50Hz,J_{max} = 0.57T and atf = 400Hz,J_{max} = 0.10T. Measurements are carried out on samples in a stress-relieved state and with magnetic anisotropies induced by stress or field annealing. Atf = 50Hz, a minimum m Ptversus σ is observed. The σ-value (sigma_{min}) corresponding to the minimum PTincreases with increasing |Ku|. Atf = 400Hz, a minimum in PTversus σ is observed in the samples with induced magnetic anisotropy, whereassigma_{min} = 0in the stress-relieved samiales. However, no correlation between andsigma_{min}and Kuis possible from the present data. View full abstract»

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  • Effect of field annealing angle on the magnetic properties of an amorphous Fe-B-Si-C alloy

    Page(s): 908 - 910
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    Annealing amorphous ribbons in a field in the plane at an angle to the long axis induces an easy axis also at an angle to the long axis and decreases the domain width. These effects result in a decrease in the 60-Hz losses and for domain rotations of less than approximately 5°, there is no increase in exciting voltamperes or decrease in remanence. For domain rotations of greater than about 5° the losses continue to decrease, but the exciting voltamperes increase and the remanance decreases. These effects are consistent with the domain rotation induced by the annealing. View full abstract»

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  • Vector potential and magnetic field of current-carying finite arc segment in analytical form, part II: Thin sheet approximation

    Page(s): 911 - 917
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    Analytical expressions for the components of the vector potential and magnetic field of a thin circular conic cylinder segment of arbitrary azimuthal and axial length, and carrying a constant peripheral current are derived. All the expressions developed consist of known functions such as Jacobian elliptic functions, and complete and incomplete elliptic integrals of the first, second, and third kind and thus permit a new time-saving efficient computation algorithm. View full abstract»

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  • Finite element analysis of leakage magnetic flux from an induction heating system

    Page(s): 917 - 920
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    The finite element method is applied to calculate the leakage magnetic field from an induction heating system consisting of an exciting coil and a conducting circular plate. The basic technique of the method is to draw a mathematical sphere to enclose the system. The total energy functional is assumed to be given by the interior and exterior functionals. The former is represented by using the usual axisymmetric triangular elements. On the other hand, the latter is given in a simple form by expanding exterior fields in terms of the solutions of a differential equation governing exterior empty spaces. The interior and exterior potentials are then matched on the spherical interface. After the validity of the method is verified by comparing results with analytic solutions for a single coil, the leakage magnetic flux from an induction heating system is computed at large distances. View full abstract»

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  • Principles of three-dimensional magnetohydrostatic axial separation system

    Page(s): 921 - 928
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    A three-dimensional magnetohydtostatic axial system comprises a magnetic field with its gradient set high vertically and low horizontally. The vertical gradient is used for levitation, with its axial rate of change monitored through the horizontal gradient. Useful fields are obtainable with pole faces generating a two-dimensional potential function multiplied by an axial function which obeys the Laplace equation; a tilted two-dimensional profile produces the same apparent effect. Experiment and theory show that the resolving power of the axial system is superior to that of its two-dimensional counterparts. View full abstract»

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  • Magnetoelastic soliton

    Page(s): 929 - 930
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    For the stationary solitary magnetoelastic waves (magnetoelastic solitons) propagation along the equilibrium direetions of ferro-and antiferromagnetic vectors M and L in uniaxial crystals, exact solutions of coupled magnetization motion equations (Landau-Lifshitz) and elastic equations are obtained. The types of oscillations depending on the propagating velocity are determined. It is shown that velocity spectrum in the vicinity of sound velocity has a gap of magnetoelastic origin where oscillation character changes. Changing of oscillation type can also take place near the maximum propagating velocity of the magnetoelastic soliton. View full abstract»

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Aims & Scope

IEEE Transactions on Magnetics publishes research in science and technology related to the basic physics and engineering of magnetism, magnetic materials, applied magnetics, magnetic devices, and magnetic data storage.

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Meet Our Editors

Editor-in-Chief
Pavel Kabos
National Institute of Standards and Technology