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In this work, the influence of the magnetic field on the alignment degree of the magnetic particles and on the magnetic energy flux of elastomer bonded magnets are investigated. For the investigations, a strontium ferrite filled nitrile butadiene rubber is used. The change of magnetic flux density in the injection molding tool cavity was realized by changing the current at the rectifier. The alignment degree of the magnetic particles increases with increasing magnetic field in the injection molding tool cavity. Above a certain current strength, a saturation behavior of the alignment degree of the magnetic particles and the magnetic energy flux is reached. The change of the cavity magnetic field leads to an improvement of the pole angle error up to a current of 10 A. An increase of the current above 10 A leads to hardly any improvement of the pole angle error, since a saturation in the alignment of the magnetic particles has already been reached. KEYWORDS alignment degree, bonded magnets, elastomer, magnetic field, magnetic filler, strontium ferrite, 1 | INTRODUCTION In the future, permanent magnets will be strongly represented in various areas such as electric cars, robotics, or household applications. These magnets generate a magnetic field that [...]

A novel silver hexacyanoferrate nanoparticles (AgHCFNPs) were synthesized through one step controllable electrochemical deposition. An AgHCFNPs/multi-wall carbon nanotubes (MWNTs)/Nafion modified glassy carbon electrode (GCE) was fabricated. Scanning electron microscopy (SEM) and electrochemical methods were used to characterize the AgHCFNPs/MWNTs/Nafion/GCE. The SEM images showed that the AgHCFNPs was evenly immobilized on MWNTs. The size of AgHCFNPs was examined around 100 nm. The AgHCFNPs/MWNTs/Nafion/GCE was used for the determination of phenol in 0.1 M K[H.sub.2]P[O.sub.4]--0.1 M [K.sub.2]HP[O.sub.4] buffer solution (pH 8.0). Under the optimal conditions, the current response of phenol increased linearly with its concentration from 0.6 to 60.0 µM, and the limit of detection was found to be 0.2 µM. The practical application of the present modified electrode was demonstrated by measuring the concentration of phenol in real water samples. Keywords: silver hexacyanoferrate nanoparticles, multi-wall carbon nanotubes, phenol, electroanalysis DOI: 10.1134/S1061934815090154, Aqueous aromatic compounds are human health-hazard chemicals and their pollution is considered a serious problem due to their known toxicity at low concentrations [1]. Phenol is often used as a [...]

This paper presents the use of the Jiles-Atherton model in fitting the major magnetization curves for two classes of composite magnetoelectric materials. These materials are: [(BaTi[O.sub.3]).sub.x][(Co[Fe.sub.2][O.sub.4]).sub.1-x] and[(BaTi[O.sub.3]).sub.x][(Co[Mn.sub.0.2][Fe.sub.1.8][O.sub.4]).sub.1-x], with x = 0.8, 0.6, and 0.4. The model's parameters result from finding the regression curves and give information about the micromagnetic state of the material. The dependencies of the model's parameters on the ratio of the two phases' concentrations have been analyzed. The values of the parameters for the two classes of materials have been compared, and the influence of Mn on the magnetic properties has been analyzed. Also presented here are the regression curves for a set of first order reversal curves using the same algorithm as the major magnetization curves. The dependence of the model's parameters on the reversal field has been analyzed. PACS Nos: 75.60.-d, 75.60.Ch, 75.60.Nt, 75.60.Ej Resume : Nous presentons ici le modele de Jiles-Atherton pour ajuster numeriquement les caracteristiques magnetiques majeure dans deux classes de materiaux composites magnetoelectriques. Ce sont le [(BaTi[O.sub.3]).sub.x][(Co[Fe.sub.2][O.sub.4]).sub.1-x] le [(BaTi[O.sub.3]).sub.x][(Co[Mn.sub.0.2][Fe.sub.1.8][O.sub.4]).sub.1-x],avec x = 0,8, 0,6 et 0,4. Les parametres du modele, obtenus des courbes de regression, nous renseignent sur l'etat micromagnetique du materiau. Nous analysons la dependance des parametres du modele sur le rapport de concentration des deux phases, comparons la valeur des parametres pour les deux classes de materiaux et analysons l' influence du manganese sur les proprietes magnetiques. Nous obtenons egalement les courbes de regression pour un ensemble de << first order reversal curves >> , en utilisant le meme algorithme que pour les caracteristiques magnetiques majeures et etudions la dependance des parametres sur l'inversion. [Traduit par la Redaction], 1. Introduction The development of magnetoelectric composite materials from raw material with high magnetostriction and piezoelectric coefficients has received great attention during the last years due to their possible applications [...]

In this paper, PCB embedded power inductors have been designed, fabricated, and characterized for low power compact DC-DC converter applications by using screen-printing and low temperature processing technologies. These proposed power inductors were comprised of screen-printed Ni-Zn soft ferrite composite cores and two layer vertically stacked spiral type coils. The double stacked spiral coil geometry was applied to reduce the size and to increase the inductance value of the proposed power inductor. The fabricated power inductor with double stacked circular type coils and 9 windings exhibited an inductance of 0.81 [micro]H, a quality factor of 45 at 10 MHz, and a DC rated current of 470 mA. Its size (4.5 mm x 4.5 mm x 0.5 mm (height)) was much smaller than the previously reported devices. The circular type power inductors had smaller size and better performance characteristics than the rectangular type ones. Index Terms--Composite material, low temperature process, Ni-Zn ferrite, PCB, power inductors, screen printing.

The thermal reduction of metal oxides as part of a thermochemical two-step water-splitting cycle requires the development of a high-temperature solar reactor operating at 1000-1500[degrees]C. Direct solar energy absorption by metal-oxide particles provides direct efficient heat transfer to the reaction site. This paper describes the experimental results of a windowed small reactor using an internally circulating fluidized bed of reacting metaloxide particles under direct solar-simulated Xe-beam irradiation. Concentrated Xe-beam irradiation directly heats the internally circulating fluidized bed of metal-oxide particles. Ni[Fe.sub.2][O.sub.4]/m-Zr[O.sub.2] (Ni-ferrite on zirconia support) particles are loaded as the working redox material and are thermally reduced by concentrated Xe-beam irradiation. In a separate step, the thermally reduced sample is oxidized back to Ni-ferrite with steam at 1000 [degrees]C. The conversion efficiency of ferrite reached 44% ([+ or -]1.0%), which was achieved using the reactor at 1 kW of incident Xe lamp power. The effects of preheating temperature and Ni[Fe.sub.2][O.sub.4]/m-Zr[O.sub.2] particle size on the performance of the reactor for thermal reduction using an internally circulating fluidized bed were evaluated. [DOI: 10.1115/1.3027511]

This paper presents, for the first time, a tunable left handed coplanar waveguide zeroth-order resonator on a ferrite substrate. Analysis and design procedures of the proposed resonator are introduced. The proposed resonator is designed to be tuned over the frequency band from 3 to 4.85 GHz with lower than 3-dB insertion loss and better than 10-dB return loss. The dimensions of the proposed resonator are 8.3 x 20 mm. The advantages of the proposed resonator are its tuning capability in addition to its compact size. Index Terms--Ferrite, left-handed media, metamaterials, resonator.

An integration methodology is presented to design antenna systems incorporating a ferrite circulator. Two integrated systems comprised of a microstrip circulator and Yagi planar--type antennas are presented as validation of the proposed methodology. Excellent pass band characteristics are observed in the experimental and numerical data for both systems. Furthermore, one system is magnetically tuned to realize 30 dB isolation over a bandwidth of 850 MHz. Both systems maintain excellent return loss and show improved insertion loss specifications even though the ferrite is biased into partial saturation. Extensive measurement data of the ferrite material and system network parameters are provided to corroborate the claims made herein. Index Terms--Ferrites, microstrip antennas, microwave circulators, Yagi-Uda arrays.

As landfills mature, biodegradable matter in leachate is consumed and remaining compounds are increasingly recalcitrant. In this work, ferrate was compared to Fenton's reagent for the purpose of removing nonbiodegradable organic compounds from mature leachate. Oxidation conditions (time, pH, and dose) were optimized to yield maximum organic removal using two leachate samples from 20- and 12-year-old solid waste cells. Results from this study demonstrated that Ferrate and Fenton's reagent had similar optimum pH ranges (3-5), but different organic removal capacities, ranging from 54 to 79% of initial leachate organic contents. An advantage of ferrate was that it was effective over a wide pH range. Advantages associated with Fenton's reagent include that it had higher organic removal capacity, produced more oxidized organic compounds (measured as chemical oxygen demand/dissolved organic carbon), and produced more biodegradable byproducts (measured as chemical oxygen demand/5-day biochemical oxygen demand). Finally, both treatments were found to attack larger molecules (> 1,000 Dalton), as indicated by an increase in smaller molecule contribution to organic carbon. DOI: 10.1061/(ASCE)0733-9372(2007)133:11(1042) CE Database subject headings: Oxidation; Chemical treatment; Landfills; Leaching; Organic compounds; Dissolved organic carbon; Biodegradation; Chemical oxygen demand.

Abstracts: Magnetic papers have been successfully prepared from unbleached kenaf (hibiscus cannabinus) kraft pulps via the lumen loading and in situ synthesis process. The lumen loading method allows the magnetic [...]

To understand the influence of cast iron microstructure on its machinability, a numerical model that simulates machined material on a microstructure scale was developed. This microstructure-level model assembles individual constituents into a composite material based on microstructural composition, grain size, and distribution. Extensive experimentation was performed to determine strain, strain rate, temperature, and load history dependent material properties. The purpose of this work is to validate the microstructure-level model on machining of ductile iron and two of its constituents: pearlite and ferrite. Orthogonal cutting experiments were conducted of the three materials. The measured chip morphology and machining forces were compared with the model predictions, and a good correlation between them was found. [DOI: 10.1115/1.1557295]

A mechanistic model for the micro-endmilling process is developed that explicitly accounts for the different phases while machining heterogeneous materials. It is shown that frequencies in the cutting force signal higher than those that can be explained by the kinematics of the process can be explained by considering the multiple phases in the material. Experiments are performed on two compositions of ductile iron, pure ferrite and pearlite workpieces. These experiments show that the nature of the variation in the ductile iron cutting force signals can be attributed to the mixture of the phases. Additionally, simulation studies show that the frequency component of the variation is related to the spacing of the secondary (ferrite) phase and the magnitude of this component is determined by the size of the secondary phase particles. [DOI: 10.1115/1.1556402]

A novel approach toward the removal of iron and nonferrous metals from typical South African acid mine drainage (AMD) waters was investigated. The approach involves the controlled oxidation of ferrous-containing AMD water at ambient temperatures in the presence of magnetite seed. The resulting oxidation product is the ferrite ([M1.sup.3+.sub.2][M2.sup.2+][O.sub.4]) magnetite ([Fe.sub.3][O.sub.4]) which has the capacity for nonferrous metal removal by cation substitution. Mossbauer spectroscopy, x-ray diffraction, and scanning electron microscopy analyses confirmed the precipitant to be magnetite. The effects of four parameters are reported: airflow rate, seed concentration, pH, and temperature. All of these independently affect the % ferrous in the final precipitant. In all experiments, the airflow rate was found to be rate limiting with respect to the kinetics of ferrous removal. The retention time for the complete removal of 1,200 mg Fe/L was 0.3-1.6 h (corresponding to airflow rates of 0.05-0.6 L/min, respectively). The precipitant settled well and showed complete stability at pH 5. The total iron concentration in the raw effluent was always less than 1 mg/L, representing an iron removal efficiency of greater than 99.9%. CE Database keywords: Oxidation; Acid mine water; Wastewater treatment.

Acting as a powerful oxidant, efficient coagulant, and effective disinfectant, ferrate is a good multifunctional agent for water and wastewater purification. In this study, some of these key aspects were studied for treating water containing fulvic acid, including the reduction efficiency of fulvic acid (FA) in drinking water and the optimum conditions for reducing FA using ferrate prepared in the laboratory. Jar tests and pilot tests were employed in the studies and the results of FA reduction were analyzed spectrophotometrically. Ferrate in these tests exhibited good oxidation capacity on FA. The ultraviolet absorption (UVA) of 2 mg/L FA in water can be reduced about 90% when the weight ratio of ferrate to FA was 12:1. Adsorption to and coprecipitation with Fe[(OH).sub.3] precipitate produced by ferrate decomposition can also result in additional FA reduction. In the presence of turbidity, ferrate can oxidize and adsorb simultaneously and over 95% of UVA was reduced with the same weight ratio of 12:1. Combining the application of ferrate and polyaluminum chloride (PAC) or iron chloride (Fe[Cl.sub.3]) was more effective for FA reduction. The UVA of 2 mg/L FA was reduced 100% in synthetic drinking water by a joint treatment with 8 mg/L ferrate (Fe[O.sup.2-.sub.4] by weight) and 0.8 mg/L PAC (Al by weight) or 6 mg/L ferrate (Fe[O.sup.2-.sub.4] by weight) and 0.8 mg/L [Fe.sup.3+] (Fe by weight). The pilot test performed more effectively for FA reduction than did the jar test. CE Database keywords: Ferrates; Oxidation; Coagulation; Acids; Potable water; Water treatment.

In this paper, the nodal finite-element method is used to analyze the differential phase shift of a nonreciprocal remanence ferrite phase shifter in a grooved waveguide. Instead of the former twin-slab model, an improved analytical model is adopted, where the effect of every part of a ferrite toroid on the differential phase shift has been considered. This analysis may replace the correcting factor with good agreement with the experimental data. Furthermore, this analysis is employed to investigate the effect of corner chamfering on the figure-of-merit (differential phase shift per decibel insertion loss) of a ferrite phase shifter. The numerical results are found to agree with the experiments in the literatures. Index Terms--FEM, ferrite toroid corner chamfering, grooved waveguide, improved analysis, nonreciprocal remanence ferrite phase shifter.

A numerical code has been developed for the full-wave determination of the resonant frequencies and quality factors of microstrip patches with right-angle corners of arbitrary shape in the case in which the substrate of the patches is a magnetized ferrite with arbitrarily oriented bias magnetic field. The code is based on the solution of an electric-field integral equation by means of Galerkin's method in the spectral domain. The evaluation of the infinite integrals arising from the application of the numerical method is efficiently carried out by means of a technique based on the interpolation of the spectral dyadic Green's function. The numerical results obtained indicate that microstrip patches fabricated on ferrite substrates present cutoff frequency regions in which resonances cannot occur owing to the excitation of magnetostatic modes. The limits of these cutoff regions are shown to be dependent on the orientation and the magnitude of the bias magnetic field, on the shape of the patches, and even on the nature of every particular resonant mode. The numerical results also show that the resonant frequencies of microstrip patches on magnetized ferrites can always be tuned over a wide frequency range provided the orientation of the bias magnetic field is suitably chosen. Index Terms--Magnetic tuning, magnetostatic modes, microstrip resonators, microwave ferrites, spectral-domain approach.

The development and current status of microwave ferrite technology is reviewed in this paper. An introduction to the physics and fundamentals of key ferrite devices is provided, followed by a historical account of the development of ferrimagnetic spinel and garnet (YIG) materials. Key ferrite components, i.e., circulators and isolators, phase shifters, tunable filters, and nonlinear devices are also discussed separately. Index Terms--Ferrite circulators, ferrite isolators, ferrite materials, ferrite phase shifters, YIG filters, YIG limiters.

This paper presents a compilation of the important milestones in the development and applications of microwave technology from the time of Hertz until 1980. The years from 1980 to the present are not addressed since this period will be covered in depth in other papers of this TRANSACTIONS. The primary technology areas addressed are electromagnetics, guided microwave structures, free-space propagation, power generation using tubes and solid-state devices, passive devices, microwave integrated circuits, ferrites, microwave acoustics, and microwave biological effects. The primary application areas are communications, radar, heating, and medical applications. Design techniques, measurements, and instrumentation are also discussed. Index Terms--Microwave applications, microwave detection, microwave ferrites, microwave generation, microwave history, microwave integrated circuits, microwave passive devices, microwave solid-state devices, microwave tubes, waveguides.

Research demonstrates mechanistic pathways for the conversion of methanol to formaldehyde by transition metal complexes, ferrate and protonated ferrates, using density functional theory approach. The reaction pathway follows an addition-elimination mechanism by O--H cleavage to Fe--O bond containing intermediate, which undergoes a C--H cleavage forming a formaldehyde complex.

Refrigerator magnet (RM)-based demonstrations of scanning probe microscopy, magnetic field imaging, and magnetic read-and-write processes suitable for the classroom are explored. Flexible-sheet RMs, such as promotional items, can be used for experiments. The nature or these sheet magnets, which have U-shaped field lines for a complex and ingenious magnetic structure, and their manufacture, which involves an array of permanent magnets forming the magnetic stripes as a sheet of ferrite-Hypalon composite passes by the array, are explained. Hypalon is an elastomer, the structure for which is given

Partially magnetized ferrites play an important role in a large class of microwave devices. For instance, when the optimal design of circulators, which operate with ferrite in the low magnetic field region, and other ferrite devices (phase shifters, isolators etc.) are considered, permeability tensor is required for arbitrary magnetization. The existing models do not simultaneously provide all tensor components, and their validity domain is limited. The proposed model provides integral expressions for all permeability tensor components, which can be treated numerically without difficulties. The physical nature of the model enforces the causal aspect that is required when numerical time-domain methods (such as finite-difference time domain (FDTD), transmission-line matrix (TLM), time-domain finite-element method (TDFEM), etc.) are used. Finally, the comparison with measurements or specific cases, which can be treated by available models, demonstrates the validity of the proposed approach.

Ferrites are heavy metals that have been suggested as a solution to the problem of acid mine drainage (AMD) in the mining industry owing to its ferromagnetic behavior. Although effective in solving AMD, miners face the problem of forming ferrite at ambient temperatures. A study investigating the relationship between an ambient temperature ferrite process and AMD identified the molar ratio of Fe3+ to Fe2+ as the critical parameter of ferrite formation.

Switchable antennas consisted of microstrip elements with an in-plane biased ferrite cover layer are introduced. Their radiation and radar cross section (RCS) properties are examined through a full-wave moment-method analysis. For microstrip antennas with a ferrite cover layer, the presence of a decaying extraordinary wave in the ferrite layer can reduce or prohibit incident fields from reaching the antenna resulting in significant RCS reduction. For antenna radiation, most of the power will be converted into magnetostatic waves and little radiates into the air. Under such circumstances, the antennas are 'off,' in the sense that they are effectively absent as radiators or scatterers. The aim of this paper is, through the use of an accurate full-wave analysis, to investigate the properties of the switchable microstrip antennas. Both the cases of strip dipoles and rectangular patches are analyzed. The effects of the cover-layer thickness, bias-field strength, and the existence of both ordinary and extraordinary waves on the switchable antenna properties are discussed.

A wide-band design method of an electromagnetic wave absorber with using exponentially tapered ferrite, which has very wide-band frequency characteristics, is proposed and discussed. The wide-band electromagnetic wave absorber can be designed under some approximations by the theoretical model using the equivalent material constants method for the regions varying spatially in the shape of ferrite. Based on the model, wide-band electromagnetic wave absorbers with taper, which have not only excellent reflectivity frequency characteristics but also the band width of 30 MHz to 2150 MHz or 2430 MHz under the tolerance limits of -20dB reflectivity, were designed.

Low-temperature-fired ([Ni.sub.0.4-x][Mg.sub.x][Cu.sub.0.2][Zn.sub.0.4])[Fe.sub.1.96][O.sub.4] ferrites with x = 0, 0.1, 0.2, 0.3, and 0.4, have been synthesized by the conventional mixed oxide method and investigated their electromagnetic properties. Initial permeability is observed to increase with increase in Mg substitutions. At the same time, sintering density, magnetic flux density, remanence, coercivity, and Snoek's product decrease with increase in Mg substitutions. Furthermore, microstructures and permittivity spectra have no obvious changes with Mg substitutions. Possible mechanisms contributing to the above results are discussed. Index Terms--Crystal microstructure, ferrites, permeability, permittivity.

The soft-heating method is one kind of heating technique of hyperthermia. The feature of this method is to use thermosensitive magnetic material as the heat element. This means the heat element can control the temperature automatically, referring the Curie-point of the thermosensitive ferrite. The heat element consists of a thermosensitive ferrite and metal ring. The purpose of the metal ring wrapped to ferrite is to increase heat quantity compared with that of ferrite alone. In this study, the effect of the heat element in mouse tumor model (B-16 melanoma) is examined. As a result, the tumors of mice were locally heated to the point at which tumor is necrotized in the condition of 200 kHz-6 mT. Index Terms--Hyperthermia, mouse melanoma, soft-heating method, thermosensitive ferrite.

Newly designed transeutaneous energy transmission system for a ventricular assist device was developed. We obtained higher dc-dc efficiency of 93.4% and smaller size of devices. Also, the devices were designed in view of the biomedical compatibility, gradually sloped coils and the flexibility of the primary coil prevent pressure necroses of the skin. The rectifier circuit board was placed in the internal space of the ferrite core to reduce the number of the implanted devices. However, radiated outward ground patterns were adopted to achieve a balance between thermal radiation and reduction of eddy-current loss. Index Terms--Artificial heart, contactless power supply, digital phase-locked loop (PLL), synchronous rectification.

To make removable, flexible disk drives (FDDs) a practical solution for modern backup, archiving, and data sharing, current areal density capabilities must be improved. In this paper, we study prototype drive-level performance of two types of flexible media. Using giant magneto-resistive heads, a partial-response maximum-likelihood channel, and a robust error-correction coding scheme, we evaluated signal-to-noise ratios, byte-error rates, pulse widths, and off-track read capabilities for each media type. Our results demonstrate the feasibility of FDD areal densities at 17.5 Gb/[in.sub.2] using barium-ferrite particulate media, and 31 Gb/[in.sub.2] using CoPtCr-Si[O.sub.2] sputtered media. Index Terms--Areal recording density, barium-ferrite, CoPtCr-Si[O.sub.2], flexible disk, magnetic recording.

The feasibility of a high-density magnetic particulate recording medium with a thin magnetic layer of evenly dispersed high-coercivity barium-ferrite particles was investigated. Thermal stability, writability, and an areal recording density of 17.5 Gb/[in.sub.2] were confirmed for a flexible disk system using a giant magnetoresistive head. Index Terms--A real recording density, barium-ferrite, flexible disk, giant magnetoresistive (GMR) head, particulate media.

The influence of the modulation and parametric four-magnon instabilities on the propagation of magnetostatic surface wave (MSSW) pulses in a delay line configuration has been experimentally studied in a ferrite-dielectric-metal structure. It was possible to distinguish the influence of both instabilities by changing the dispersion properties of the exploited device. The contribution of additional MSSW continuous wave and pulsed signals on the propagation of MSSW pulses has been also considered. Index Terms--Nonlinear microwave ferrite, microwave devices, solitons, thin films.

Magnetic (static, high-frequency) and microwave-absorbing properties of Co-substituted [Ni.sub.2]W hexaferrites are investigated in the frequency range of Ka-band (26.5-40 GHz). The powders of composition Ba[Ni.sub.2-X][Co.sub.X][Fe.sub.16][O.sub.27] are prepared by calcining at 1250[degrees]C, where the substitution ratio x was varied from 0.0 to 1.4. With the calcined powders, the composite specimens are prepared using the silicon rubber as a matrix material. Vibrating sample magnetometer measurement indicates that the coercivity of the specimens of Ba[Ni.sub.2-X][Co.sub.X][Fe.sub.16][O.sub.27] decreases with Co substitution, which is attributed to a reduction of crystal anisotropy field by changing the easy-axis of magnetization from c-axis to basal plane. The complex permeability spectrum shows the decrease of resonance frequency with Co substitution. The specimens with composition of x = 0.2 and x = 0.4 show the superior microwave absorbing properties in Ka-band. For the specimen of x = 0.4, the bandwidth (with respect to--20-dB reflection loss) is 26.5-32 GHz at a matching thickness of 0.9 mm. The Co substituted [Ni.sub.2] W-hexaferrites can, therefore, be suggested as a good absorbing material for the electromagnetic radiation in the frequency range of Ka-band. Index Terms--Absorber, hexaferrite, Ka-band, [Ni.sub.2]W.

Ferrite co-fired with dielectric materials and pure silver below 900 [degrees] C is the key issue in the production process for multilayer chip LC filters. The addition of glass to Ti[O.sub.2] reduced the sintering temperature, improved the characteristics of the dielectric constant and decreased the dissipation factor below 0.1% at I MHz. The glass induced the silver to diffuse quickly into the interface of the ferrite and the doped Ti[O.sub.2] dielectric ceramic as well as the surface. Glass will deteriorate the dielectric properties and worse the attenuation and the noise filtering ability in the processed, LC filter, ferrite and Ti[O.sub.2] dielectric ceramic without glass doping can be processed for good performance multilayer chip LC filters. Index Terms - Multilayer chip LC filter, Ferrite, Glass, Silver

A compound n:1 transformer useful for inverting, noninverting or balun type wide-band transformer is described. We derived equivalent circuits of the transformers, and analyzed them taking into account frequency characteristics of the specific magnetic permeability [Mathematical Expression Omitted] of ferrite core material. We constructed compound [-square root 2]: 1 transformers using small ferrite cores (outer diameter = 2mm), and measured them over wide frequency range (0.1 [approximately] 2000MHz). The theoretical and measured transformer characteristics are in good agreement. Index Terms - Compound n:1 transformer, ferrite core, frequency characteristics of [Mathematical Expression Omitted], noninverting wide-band transformer.

Low profile transformers are required to miniaturize power supplies. Core materials used in low profile transformers must have low core losses at the MHz range. A fine grained Mn-Zn ferrite has been developed for high frequency driving at the MHz range. The ferrite shows considerably less core losses than a conventional Mn-Zn ferrite. The transformer using the ferrite exhibited high efficiency and a lower surface temperature.

We have fabricated a linear dipole array antenna containing four elements fed by ferrite phase shifters. The steering properties of the array have been thus measured. At f = 10 GHz, the radiation beam was steered 23 [degrees] when the bias field was changed from 2775 to 2874 Oe.

A disorder of conduction system causes cardiac arrhythmia. At present, electromagnetic waves such as radiofrequency waves are generally used for the ablation. However, the radiofrequency ablation often accompanies fatal side effects. We developed the new method of catheter ablation using temperature-sensitive ferrite rod and a non-magnetic metal ring as a heating device. The device generates heat in an impressed magnetic field that does not generate heat in body itself. The maximum temperature is determined by the Curie temperature of the ferrite rod. The clinical application of the method was discussed experimentally. The results suggest that the usefulness of this method for conduction system ablation in the treatment of ventricular arrhythmia.

Porous silica microspheres, 1-3 [[micro]meter] in diameter, were coated with [Fe.sub.3][O.sub.4] by 'reactor method' ferrite plating. The polycrystalline [Fe.sub.3][O.sub.4] coating was synthesized from an aqueous solution (pH = 7.3) of Fe[Cl.sub.2] at 60-70 [degrees] C, using oxidizing solution of NaN[O.sub.2] mixed with C[H3]COON[H.sub.4] (pH buffer). The magnetite capsulated silica microspheres can be potentially used for contrast agents for clinical ultrasonography, especially for blood flowmetry; the air trapped in the silica pores enhances the ultra-sound echogenicity. The contrast agents are controllable by magnetic fields, and their virtual density can be adjusted to that of ambient fluid by changing the thickness of the [Fe.sub.3][O.sub.4] coating.

We have formulated the operation of an isolated ferrite patch antenna of circular geometry. The cavity model has been applied to the ferrite region below the patch disc in the prediction of radiation frequencies. The theory compares very well with measurements. A ferrite patch antenna array has been fabricated which clearly shows the steering property of the biasing magnetic field.

We have formulated the operation of a drop-on circulator in which a ferrite disc is directly placed on top of a dialectric substrate. The cavity model has been applied both to the ferrite disc and the dielectric region below and around the ferrite disc. Three circulators were fabricated using design parameters calculated by our theory. The measurements are in reasonable agreement with predicted performance of the device.

The complex permeability dispersions and the microwave absorbing phenomena are investigated in ferrite microwave absorbers. The complex permeability of hexagonal (Y- and Z-type) and spinel (NiZn ferrite and NiZnCo ferrite) ferrites microwave absorbers were measured in 200MHz-16GHz range. The theoretical matching frequencies are determined by plotting the measured complex permeability loci on the impedance matching solution map. One or two impedance matching phenomena are observed in the ferrite absorbers according to their complex permeability loci on the impedance matching solution map. It was discovered that the 1st matching frequency (f(sub m1)) of the ferrite absorber strongly depends on its spin resonance frequency (f(sub r2)) and the 2nd matching frequency (f(sub m2)) is independent of the resonance frequency.

A dielectric image guide loaded with a self biasing ferrite was designed and tested from 26.5 to 40 GHz. An M-type hexagonal ferrite was used with its c-axis transverse to the direction of propagation. The electromagnetic scattering parameters of the device were measured for the magnetic field applied along the c-axis. We have employed two different methods to analyze the guided structure-a) transmission line circuit model and b) perturbation theory. General agreement was found between the transmission line analysis and the experimental results.

A new heating device using a small heater made of temperature sensitive ferrite and gold ring was developed for clinical application of interstitial hyperthermia. The temperature characteristics were evaluated and the influence of irradiation with gold was examined. The device had the characteristics of regulating the temperature accurately and automatically. Gold enhanced the effect of irradiation. This method is useful and safe for interstitial hyperthermia of malignant brain tumors and it can be applied clinically.

A design procedure for the construction of a self-biased hexaferrite waveguide circulator was discussed. It was shown that the necessary parameters of the hexaferrite material need to be measured with a simple microwave technique. The importance of choosing the right material with a proper value of the internal anisotropy field was stressed. The procedure for the dimensioning of the ferrite insert and the spacers was presented.