# Showing papers in "IEEE Transactions on Magnetics in 1983"

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TL;DR: Two general methods for the deduction of global information from the final result of the finite element computation of an electromagnetic device, called the local jacobian derivative and the stationary property of the field solution are presented.

Abstract: The paper will present two general methods for the deduction of global information from the final result of the finite element computation of an electromagnetic device. The first one, called the local jacobian derivative, may be used for evaluation of the derivative of any integral quantity versus the parameter of motion of a rigid body. Typically, this method when applied to electromagnetic systems, can be used for the computation of magnetic force or torque by virtual-work principle. Compared with the popular Maxwell's tensor method, this procedure is easier to implement in a finite element package especially for 3D problems. The second method which is based on a stationary property of the field solution, allows the evaluation of a second order derivative of any integral quantity. For instance, computation of the stiffness of a magnetic system (derivative of a force or a torque) may be achieved as the second order derivative of the magnetic energy. It may be pointed out that this method requires the field computation once for a linear problem as well as for a non-linear one.

359 citations

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TL;DR: In this paper, an equation describing the initial magnetisation curve and hysteresis loops of ferromagnetic materials has been derived theoretically based on a mean field approximation, where the mutual interaction of the moments is expressed as a coupling coefficient and a restraining force on the motion of the domain walls, caused by the pinning of the walls at defect sites, is expressed by a pinning coefficient.

Abstract: An equation describing the initial magnetisation curve and hysteresis loops of ferromagnetic materials has been derived theoretically based on a mean field approximation. The mutual interaction of the moments is expressed as a coupling coefficient and a restraining force on the motion of the domain walls, caused by the pinning of the walls at defect sites, is expressed as a pinning coefficient. The resulting equation of state for the model is a first order linear differential equation incorporating the two parameters and a scaling parameter λ which represents the ratio of the coupling to the two fields H and M.

313 citations

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TL;DR: Two applications of the variational formulation of the eddy-currents problem using the magnetic field h as state variable are described: computation of the impedance of a probe in non-destructive testing and prediction of the characteristics of a new design of an iron-free machine.

Abstract: In [1] and [2], a variational formulation of the eddy-currents problem using the magnetic field h as state variable was introduced. We describe here two applications of the method: computation of the impedance of a probe in non-destructive testing and prediction of the characteristics of a new design of an iron-free machine. The basic idea is first exposed, leaving aside difficulties like multiple connectedness. These are treated more thoroughly in Part 3, after the description of applications in Part 2.

172 citations

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TL;DR: In this paper, a new magnetic solid state memory is proposed, which utilizes usual bubble garnet films, which is composed of a conductor-drive bubble-propagation major line and long stripe domains aligned in parallel which constitute minor loops to accommodate vertical Bloch line pairs.

Abstract: A new magnetic solid state memory is proposed, which utilizes usual bubble garnet films. The "1" or "0" is stored by the presence or absence of a negative vertical Bloch line pair in the stripe domains. The memory chip organization is composed of a conductor-drive bubble-propagation major line and long stripe domains aligned in parallel which constitute minor loops to accommodate vertical Bloch line pairs. When doing the writing, the presence and absence of the bubbles in the major line is converted to the presence and absence of the vertical Bloch line in the storage area. When doing the reading, the reverse is true. The Bloch line pair is replicated in the stripe domains, and the converted bubbles are detected by the usual stretcher detector. The Bloch lines propagate under the successively applied bias pulsed fields. The bit density increases drastically, and we can expect around 1.6 Gbit/cm2using 0.5 μm bubble garnet films.

169 citations

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TL;DR: In this article, an informative new way of plotting magnetization data for transition-metal alloys is described, which is used to distinguish a variety of generic alloy types including magnetically strong and weak amorphous alloys, and Co alloys with metalloids such as Si and P, exhibit regular, easily interpreted behavior.

Abstract: An informative new way of plotting magnetization data for transition-metal alloys is described. The plot is used to distinguish a variety of generic alloy types including: 1) a large class for which the magnetization data fall near a common straight line, 2) magnetically strong and weak amorphous alloys, and 3) Co alloys with metalloids, such as Si and P, exhibit regular, easily interpreted behavior. Self-consistent spin-polarized energy-band calculations are used to explain the trends revealed by the plotting construction.

162 citations

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TL;DR: In this paper, a novel formulation for eddy current calculations in 3D is derived, which promises to require the minimum set of degrees of freedom, and also to be numerically stable.

Abstract: A novel formulation for eddy current calculations in 3-D is derived.The method promises to require the minimum set of degrees of freedom, and also to be numerically Stable. A magnetic vector potential is used inside conducting regions, and it is shown that the gauge of this potential is implicit in the formulation. In non-conducting regions a magnetic scalar potential is used. The vector and scalar potentials are coupled on the interface between the two regions by the field continuity conditions, which implies zero current flow across the interface Computed results are compared with the analytic solutios of a conducting permeable sphere in an external field, and with measurements on a conducting block is a spatially varying field.

153 citations

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TL;DR: Application of the mesh generator to a variety of problems in magnetic field design shows it to be one of the most powerful and easy to use systems yet devised.

Abstract: A two-dimensional finite element analysis package is described which automatically generates optimal finite element meshes for magnetic field problems. The system combines the concept of Delaunay triangulation with variational principles to provide a grid which adapts to the characteristics of the solution. In this procedure, two different approximate solutions to the magnetic field are derived, the difference between the two approximate solutions providing an element by element measure of the accuracy of the solution. By refining those elements having the largest errors and recomputing the solution iteractively, finite element meshes having a uniforrn error density are obtained. The system is menu oriented and utilizes multiple command and display windows to create and edit the object description interactively. Matrix solution is by means of a rapid pre-conditioned conjugate gradient algorithm, and a wide variety of post-processing operations are supported. Application of the mesh generator to a variety of problems in magnetic field design shows it to be one of the most powerful and easy to use systems yet devised.

153 citations

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TL;DR: In this article, a novel circuit consisting of solid-state diodes and a biased superconducting coil is presented for limiting the fault currents in three phase ac systems, where a modification of the basic circuit results in a solid state ac breaker with current limiting features.

Abstract: A novel circuit, consisting of solid-state diodes and a biased superconducting coil, for limiting the fault currents in three phase ac systems is presented. A modification of the basic circuit results in a solid-state ac breaker with current limiting features. The operating characteristics of the fault current limiter and the ac breaker are analyzed. An optimization procedure for sizing the superconducting coil is derived.

148 citations

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TL;DR: In this article, a new switching dc-to-dc converter is synthesized which consist of the least number of storage elements (inductive and capacitive) and switches, and yet truly emulates the ideally desired dc to dc transformer having both input and output currents as pure dc quantities with no ripple.

Abstract: A new switching dc-to-dc converter is synthesized which consist of the least number of storage elements (inductive and capacitive) and switches, and yet truly emulates the ideally desired dc-to-dc transformer having both input and output currents as pure dc quantities with no ripple. This result was facilitated by implementation of a new concept termed integrated magnetics, which leads in some special switching structures to the integration of otherwise independent and separate magnetic components (inductors and transformers) into a single magnetic circuit.

145 citations

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IBM

^{1}TL;DR: The magnetic properties of RF sputtered Co-Pt alloy thin films were studied as a function of Pt content from 0 to 80 at%. At room temperature, ferromagnetic films were obtained in the range 0-32 and 40-80 at% Pt; discontinuities in the magnetization, magnetostriction and coercivity versus Pt content were observed; however no discontinuity was observed in the resistivity as mentioned in this paper.

Abstract: The magnetic properties of RF sputtered Co-Pt alloy thin films were studied as a function of Pt content from 0 to 80 at%. At room temperature, ferromagnetic films were obtained in the range 0-32 and 40-80 at% Pt. For Pt contents between 32 and 40 at%, discontinuities in the magnetization, magnetostriction, and coercivity versus Pt content were observed; however no discontinuity was observed in the resistivity. The structure of films containing about 25 at% Pt is a mixture of hexagonal and face-centered cubic (FCC) phases. At this composition the magnetostriction is small, but coercivities are large-700 to 2000 Oe-and dependent upon film thickness. The coercivities of these films do not change with heat treatment up to temperatures of 600°C but decrease markedly at 700°C. The properties of equiatomic Co-Pt film s are similar to those of bulk alloys. In particular the large coercivity observed in films after heal treatment at 500° to 700°C is due to the formation of an ordered tetragonal phase within the face-centered cubic matrix. The structure of films of about 75 at% Pt is initially a disordered face-centered cubic phase and with heat treatment beginning at 500°C an ordered face-centered cubic phase forms. The coercivity of these films (∼200 Oe) does not change with annealing at 500°C. It decreases slightly upon further annealing at 600°C to 700°C. Electron microscope observations were used to correlate the magnetic properties with film structure.

139 citations

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Hewlett-Packard

^{1}TL;DR: In this article, a model for medium noise in thin film and particulate discs is presented based on both time jitter and spectrum analyzer measurements, and a signal-to-noise ratio equal to the signal/rms noise measured at the predetection filter output gives accurate prediction of peak jitter only if the noise is measured at transitlon density giving maximum noise.

Abstract: A model for medium noise in thin film and particulate discs is presented. The model is based on both time jitter and spectrum analyzer measurements. Thin metallic film discs have different noise mechanisms from either particulate or sputtered γ-Fe 2 O 3 discs. A signal-to-noise ratio equal to the signal /rms noise measured at the predetection filter output gives accurate prediction of peak jitter only if the noise is measured at the transitlon density giving maximum noise.

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TL;DR: In this article, a generalized HGMS theory describing particle capture of ultra-fine particles is formulated and the conditions for the appearance of the dynamic and static buildup are analyzed, and a particle size criterion for the generalized and conventional theories to become coincidental is established.

Abstract: A generalized HGMS theory describing particle capture of ultra-fine particles is formulated and the conditions for the appearance of the dynamic and static buildup are analyzed. A particle size criterion for the generalized and conventional theories to become coincidental is established. Typical examples of capture of paramagnetic, diamagnetic and ferromagnetic particles are used to illustrate the consequences of the new theory.

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TL;DR: In this article, an analysis has been made of published data comprising at least six manufacturers and spanning a range of critical current density at 4.2 K, 8 T of 50 to 108 kA/cm2, and linear equations have been found to fit the data over a wide range of field B and temperature T.

Abstract: Short sample 4.2 K experimental facilities are plentiful, but equipment for measurements of current as functions of temperature and field is scarce. An analysis has been made of published data comprising at least six manufacturers and spanning a range of critical current density at 4.2 K, 8 T of 50 to 108 kA/cm2, and linear equations have been found to fit the data over a wide range of field B and temperature T. For a constant temperature of 4.2 K, the following expression holds for B in the range of 3 to 10 T: j c (B, T = 4.2 K) = j o [1 - 0.096B], where [B c2 (4.2 K)]-1= 0.096 with a standard deviation of 3% for ten samples. The constant j o can be determined for any sample from a single point measurement at a convenient field. For a constant field of 8 T, the following expression holds for T in the range of 2 to 5.5 K: j c (B = 8 T, T) = j' o [1 - 0.177T], where [T c (8 T)]-1= 0.177 with a standard deviation of less than 1%. Linear equations have also been obtained for higher fields and lower temperatures. The critical field vs temperature is B c2 (T) = B c2 (0) [1 - (T/T c (0))n], where B c2 (0) = 14.5 T, T c (0) = 9.2 K, and n = 1.7 (not 2, which is used in theoretical derivations). For more accurate critical temperature calculations above 10 T, this equation can be used with the modification B c2 (0) = 14.8 T. No one simple power law for the upper critical field holds over the whole temperature range.

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TL;DR: In this article, the application of high gradient magnetic separation to the capture of submicron-sized particles is studied and the steady state solution of the diffusion equation applicable to diffusion processes taking place under the influence of external forces is obtained.

Abstract: The application of high gradient magnetic separation to the capture of submicron-sized particles is studied. The steady state solution of the diffusion equation applicable to diffusion processes taking place under the influence of external forces is obtained. The relevance of the critical particle size to the phenomena of dynamic and static capture is discussed for various materials ranging from ferromagnetic to diamagnetic. The experimental results obtained are shown to be in satisfactory agreement with the theoretical predictions.

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Bell Labs

^{1}TL;DR: In this paper, D.C.Josephson tunnel junctions with critical current density up to 1300 A/cm2 and V m = i c R(2mV) between 15mV and 47mV at 4.2K were obtained.

Abstract: Josephson tunnel junctions of the types Nb/Al-oxide-Nb and Nb/Al-oxide-Al/Nb, where Al represents thin (∼50A) films of Al, were prepared by D.C. magnetron sputtering. The tunnel barrier was formed by in-situ thermal oxidation. Individual junctions were defined using photolithography coupled with the plasma etching technique. Junctions with critical current density up to 1300 A/cm2and V m = i c R(2mV) between 15mV and 47mV at 4.2K were obtained.

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TL;DR: In this article, a fast annealing method was proposed to improve the magnetic properties of amorphous alloys by fast heating of short electric current pulse flowing through the sample.

Abstract: A new method to improve the magnetic properties of amorphous alloys by fast annealing is introduced. The zero-magnetostrictive Fe 4.7 Co 70.3 Si 15 B 10 amorphous alloy was flash-annealed by the resistive heating of short (of the order of a second) electric current pulse flowing through the sample. The heating/cooling rate was of the order of 104-105K/min. This enables the sample to be annealed at much higher temperatures (estimated 800°C) without causing crystallization, compared to the conventional annealing methods. The maximum permeability of a zeromagnetostrictive alloy obtained by this method is higher than those obtained by the conventional annealing, with the additional benefit of smaller disaccomodation effect.

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TL;DR: In this paper, the common physical basis for active dc, residual and ac methods of specimen magnetization is described and the finite element analysis techniques originally developed for the study of fields in electrical machinery can be extended to predict electromagnetic NDT transducer signals for all three forms of specimen excitation.

Abstract: Electromagnetic field interactions with metals can be used to determine both material properties and the presence of defects. Such techniques are used widely in the nondestructive testing of critical components for aerospace, transportation, energy and metals industries where reliability, safety and product quality considerations are important. This paper describes the common physical basis for active dc, residual and ac methods of specimen magnetization and shows how finite element analysis techniques originally developed for the study of fields in electrical machinery can be extended to predict electromagnetic NDT transducer signals for all three forms of specimen excitation.

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TL;DR: In this article, high-resolution electron microscopy of a set of Sm(Co.725 Fe.20 Cu.055 Zr.02 ) 7.5 magnets has been used to characterize the structure and the size of the various micro-phases present.

Abstract: High resolution electron microscopy of a set of Sm(Co .725 Fe .20 Cu .055 Zr .02 ) 7.5 magnets has been used to characterize the structure and the size of the various micro-phases present. Our investigations of the samples, which were sintered at 1215°C, subsequently isothermally aged in steps of 50° at temperatures between 700°C and 900°C and step aged at 400°C, revealed changes in the shape and size of the rhomboid cellular microstructure with aging temperature. Lattice fringe images show the coherent precipitation of the cell boundary phase and of the cell interior phases. The platelet phase, consisting of a hexagonal 2:17 -layer, and twin boundaries have been characterized within the cell interiors. It is shown that the intrinsic coercive force, being determined by the domain wall pinning at the continuous cell boundary phase, is correlated with the morphology of the precipitation structure and depends on the heat treatment of the magnets.

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NEC

^{1}TL;DR: Sputtered Co-Pt thin films have been shown to have excellent corrosion resistance and magnetic properties as discussed by the authors, which is a new material medium for high density longitudinal recording, and they have a maximum Hc value near X=20.

Abstract: This paper describes a new material medium for high density longitudinal recording. Sputtered Co-Pt thin films will be shown to have excellent corrosion resistance and magnetic properties. Co-Pt thin films do not need a thick overcoat like plated Co-Ni-P films do, and have higher remanent flux density than ferrite thin films. Co 1-x Pt x (X=0-0.60) thin films prepared by r.f. diode sputtering have a maximum Hc value near X=20. The Hc, Bs and squareness, for 20 at.% Pt film are 1,100 Oe, 12,000 G and 0.80-0.90, respectively, at 0.1 μm film thickness. These values are not changed over 1-15 Watt/cm2power densities, corresponding to 6-85nm/min deposition rates. Films with more than 28 at.% Pt have no Bs change after immersion in water for over one month, indicating that the films are passive by this test, at least. Ni additions improve magnetic and corrosion properties. There is no Bs change for Co 0.070 Ni 0.010 Pt 0.020 films after immersion in water for over one month. Finally, 51 KFRPI linear recording density was obtained, at D 50 , using a Co 0.70 Ni 0.10 Pt 0.20 thin film disc with a 0.46 μm gap length head and a 0.12 μm head-medium spacing.

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IBM

^{1}TL;DR: In this article, a simple structure, called a moat, is proposed to reduce the probability of flux-trapping in Josephson SQUIDs, where rectangular channels in the groundplane surrounding the SQUID's provide preferred sites for trapping flux, thus preventing such flux from coupling to the SquID.

Abstract: We report experimental investigations of a simple structure, called a moat, which significantly reduces the probability of flux-trapping in Josephson SQUIDs. Proper operation of Josephson logic and memory circuits requires that the SQUIDs be free of stray magnetic flux that may become trapped in the superconducting groundplane upon cooling through the critical temperature. The problem is particularly severe for so-called holey SQUIDs which rely on holes in the groundplane to obtain suitably large device inductances. Moats are rectangular channels in the groundplane surrounding the SQUID's which provide preferred sites for trapping flux, thus preventing such flux from coupling to the SQUID. We have measured the effectiveness of moats by monitoring the flux trapped in the moats and comparing it to the flux trapped in the associated SQUID as a function of applied field. The number of flux quanta in the moat is determined by measuring the shift of the threshold curve of a two-junction SQUID coupled to the moat. The data indicates that at fields on the order of a mG, moats reduce the sensitivity of holey SQUIDs to trapped flux by at least several orders of magnitude. As the chips are cooled through T c , transient magnetic fields are produced in the metallic sample holder parts surrounding the chip by thermal-gradient-induced EMF's. The effects of such magnetic fields on the flux trapping behaviour of the SQUIDs are also reported.

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TL;DR: In this paper, the magnetic flux distribution in the grain-oriented steel core transformer is investigated with the finite element method and a mathematical model (Model II) is obtained for the reluctivity tensor.

Abstract: In this work the magnetic flux distribution in the grain-oriented steel core transformer is investigated with the finite element method. A mathematical model (Model II) is obtained for the reluctivity tensor. The model, optimized by means of experimental values of the B-H curve, predicts different directions of the magnetization field, not just along the rolling and transverse directions of the material. The results are the flux maps, as well as the reactance values and the electrodynamic forces on the windings. These results, obtained by means of the isotropic model and the anisotropic first model [1], are compared with the experimental ones.

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TL;DR: In this article, the use of numerical methods in simulating and solving problems that arise in the electroheat industry is reviewed. But the focus is on the coupled electrothermal and induction stirring problems that are typical of this industry.

Abstract: This paper reviews the use of numerical methods in simulating and solving problems that arise in the electroheat industry. Particular attention is given to the coupled electrothermal and induction stirring problems that are typical of this industry. Following a brief review of the nature of electrothermal problems, the Finite Difference, Volume Integral Equation and Finite Element simulation techniques are critically examined. It is shown that each technique has a definite role and each is illustrated with practical examples. A brief discussion of unsolved problems is presented.

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TL;DR: In this paper, a planar dc SQUID with an integral matching transformer is proposed to couple a 1 μH signal source to a 16 pH SQUID loop, which has an energy sensitivity of 1.3 × 10-32J/Hz.

Abstract: We demonstrate a new way to couple efficiently to a low-inductance, low-noise SQUID. We have built and tested a planar dc SQUID with an integral matching transformer. The measured coupling agrees with our calculations. We demonstrate that this configuration can efficiently couple a 1 μH signal source to a 16 pH SQUID loop. We have also built an uncoupled SQUID of this design that has an energy sensitivity, referred to the SQUID inductor, of 1.3 × 10-32J/Hz = 20 h over a flux range of about 0.15 φ 0 .

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TL;DR: In this paper, the authors have developed a novel process for fabricating all refractory Josephson tunnel junctions whose base and counter electrodes are composed of (Nb-NbN) double-layered films.

Abstract: We have developed a novel process for fabricating all refractory Josephson tunnel junctions whose base and counter electrodes are composed of (Nb-NbN) double-layered films. In this process, tunnel junctions have been isolated using a reactive ion etching from a junction sandwich which had been formed on an entire silicon wafer, and also the reactive ion etching has been used for patterning electrodes and insulation layers in devices. Fabricated junctions have yielded good tunneling characteristics with excellent uniformity and reproducibility. The maximum critical current density was widely changed from 300 A/cm2to 8 kA/cm2. All refractory single flux quantum(SFQ) memory cells in a 32×32 arrangement have been integrated with a 2.5 μm minimum linewidth on a chip using this process, and an SFQ cell in the memory array has been successfully operated. The maximum deviation of critical currents in the memory array was measured to be ±6.5%.

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TL;DR: In this article, a triangular mesh generator for integral equation applications is described, where the mesh quality is controlled by integers specifying for each edge (a) the number of segments, their sizing, and triangle decay rate into contiguous faces.

Abstract: A triangular mesh generator, suitable for integral equation applications, is described. Given global coordinates of the vertices of the polyhedra and topological information (edge definition and face connectivity) a triangular mesh is produced over the surfaces of all the bodies. Mesh quality is controlled by integers specifying for each edge (a) the number of segments, (b) their sizing, and (c) triangle decay rate into contiguous faces. The number of segments can be increased in regions where highest accuracy is required. Their spacing may be made uniform, or can be concentrated toward either or both vertices defining an edge.

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TL;DR: In this paper, it was shown that the change in flux density caused by a single stress cycle of fixed amplitude is proportional to the difference between the initial flux density B i and the anhysteretic flux density H i at the same field, H.

Abstract: The application of stress cycling to 1% manganese steel at low magnetic fields causes an irreversible shift in the magnetization towards the anhysteretic due to domain walls breaking away from their pinning sites under stress. The change in flux density ΔB caused by a single stress cycle of fixed amplitude \sigma_{\max} has been found to be proportional to the difference between the initial flux density B i and the anhysteretic flux density B an at the same field, H. The change in flux density as a function of stress has been found to be approximately proportional to σ.

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TL;DR: In this article, the analysis of RF electromagnetic fields is considered as a linear eigenvalue problem, for which a primitive variable approach based on the electric field, E, is given.

Abstract: This paper presents a formulation and some calculations for the three dimensional analysis of RF electromagnetic fields by using the finite element method. We adopted the penalty method to obtain an approximate solution of the stationary Maxwell equations. The discussion is focused on the analysis of electromagnetic waves as a linear eigenvalue problem, for which a primitive variable approach based on the electric field, E, is given. We confirmed the validity of this method by two dimensional calculations and developed a three dimensional calculation code MAX3D. Satisfactory results are obtained for rectangular cavities, cylindrical cavities and those cavities with smoothly deformed parts.

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TL;DR: In this article, the MO calculation for the EPR and susceptibility of Cs 3 CoCl 5 is proposed on the basis of an approximate SCF d-orbital theory.

Abstract: At the present time there is no satisfactory theory for the paramagnetic crystals which relates its energy levels to its crystal structure. In this work the MO calculation for the EPR and susceptibility of Cs 3 CoCl 5 is proposed on the Basis of an approximate SCF d-orbital theory. The results are in good agreement with experiments.

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TL;DR: A simplified version of the Fully Flexible Arnstein cable with an improved new superinsulation saving the nitrogen cooling stage is proposed, based on the corrugated tube principle and offers an economically competitive and technically superior construction compared to presently favoured watercooled cables in the power range of 1 GW or even lower.

Abstract: Field trials of a Fully Flexible Superconducting Cable (60 kV/1000 A, design Klaudy-Kabelmetal) including the necessary potheads were performed successfully in a real grid for the first time in the world during the years 1977-1980 at Arnstein (Austria). The cable met all electrotechnical and cryotechnical field and test conditions. Encouraged by this success and based on the experiences gained in Arnstein as well as on further theoretical and practical investigations, the authors propose a simplified version of the Fully Flexible Arnstein cable with an improved new superinsulation saving the nitrogen cooling stage. The proposed cable is based on the corrugated tube principle (Wellmantel-technique of Kabelmetal) and offers an economically competitive and technically superior construction compared to presently favoured watercooled cables in the power range of 1 GW or even lower. This power rating is of interest already today for the electricity supply in densely populated areas and industrial centers. Fully Flexible Superconducting Cables have the following essential advantages over other superconducting and conventional cables: 1. The cable can be fabricated in great lengths (a couple of hundred meters) at low cost with well proven methods and equipment. 2. They can be reeled, shipped, and laid like any conventional cable in individual sections. 3. They require no sophisticated expansion elements as the thermal length changes occuring during cooling cycles of the cables are compensated for thanks the elasticity of the corrugated tubes. 4. They guarantee high operational safety since only a small number of splices and joints are necessary for connecting the individual sections of the cables. 5. They offer a high lifetime compared to conventional cables. 6. They are especially suited for the transmission of base load power at power ratings down to 1 GW and at voltages of 100 - 140 kV. 7. Being superconducting cables, they offer the possibility of perfect electromagnetic shielding towards their environment. Shield currents cause practically no losses. 8. The cables require surprisingly small trench widths - an advantage which can not be achieved with any type of normal conducting cables. Consequently Fully Flexible Superconducting Cables of the corrugated tube design will be of importance in connection with electrical high power transmission in future.

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TL;DR: In this article, a new formulation for skin effect problems in current carrying conductors is presented, in which the total measurable currents in conductors rather than local current density distributions are given.

Abstract: This paper presents a new formulation for skin effect problems in current carrying conductors. The specific difficulties arising in such problems stem from the fact that total measurable currents in conductors rather than local current density distributions are required to be given. These difficulties are particularly significant in the case of three-dimensional (3-D) problems. A new approach presented in this paper attempts to circumvent these difficulties by means of special modification of field equations outside the conductors. As a result of such a modification, the total currents in the conductors appear explicitly in the formulation through the boundary conditions.