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Permanent Magnets (permanent + magnet)

Distribution by Scientific Domains
Engineering47%
Medical Sciences15%
Polymers and Materials Science10%

Terms modified by Permanent Magnets

  • permanent magnet synchronous motor
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    Selected Abstracts

    Low-energy irradiation effects of gas cluster ion beams

    ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 2 2008
    Shingo Houzumi
    Abstract A cluster-ion irradiation system with cluster-size selection has been developed to study the effects of the cluster size for surface processes using cluster ions. A permanent magnet with a magnetic field of 1.2 T is installed for size separation of large cluster ions. Trace formations at HOPG surface by the irradiation with size-selected Ar-cluster ions under an acceleration energy of 30 keV were investigated by scanning tunneling microscopy. Generation behavior of the craterlike traces is strongly affected by the number of constituent atoms (cluster size) of the irradiating cluster ion. When the incident cluster ion is composed of 100 to 3000 atoms, craterlike traces are observed on the irradiated surfaces. In contrast, such traces are not observed at all with the irradiation of the cluster ions composed of over 5000 atoms. Such behavior is discussed on the basis of the kinetic energy per constituent atom of the cluster ion. To study GCIB irradiation effects on macromolecules, GCIB was irradiated on DNA molecules absorbed on graphite surface. Using GCIB irradiation, many more DNA molecules were sputtered away compared with the monomer-ion irradiation. © 2008 Wiley Periodicals, Inc. Electron Comm Jpn, 91(2): 40,45, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.10031 [source]

    Optimum matching parameters of an MPPT unit used for a PVG-powered water pumping system for maximum power transfer

    INTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 6 2006
    Mehmet Akbaba
    Abstract Photovoltaic generator (PVG)-powered water pumping has the potential to bring potable water to millions of people in developing countries. However, due to the high initial cost of PVG units, sophisticated load matching is required between the water pumping system and PVG, in order to be able to extract maximum available power from an available PVG unit at all solar radiation levels. This requires an intermediate circuitry between the PVG unit and the motor driving the water pump, which is usually termed as maximum power point trackers (MPPT). This present paper therefore investigates the optimum matching parameters of a power conditioning circuit, which is composed of a double step-up dc,dc converter (DSUC). This MPTT circuit is used for interfacing a permanent magnet (PM) motor-driven water pumping system to a PVG for extracting maximum available power from PVG, hence maximizing the energy utilization efficiency and price,performance ratio of the whole system. It is shown that two key parameters of the DSUC, which are the duty cycle and chopping frequency, are dominating the performance of the whole system, and they are interrelated and load dependent. Therefore, optimum values of these parameters need to be determined. An example system is provided in which a complete modelling is presented in time domain and through numerical experiments it is demonstrated how the optimum values of these two key matching parameters can be determined for a given system. The MPPT circuit used in this investigation is suitable for optimum matching of all types of loads to PVG units, provided that an optimum frequency,duty cycle pair is determined for the choppers in DSUC for every 5% bands of solar radiation between 20 and 100%. Copyright © 2005 John Wiley & Sons, Ltd. [source]

    Safety of orthopedic implants in magnetic resonance imaging: An experimental verification

    JOURNAL OF ORTHOPAEDIC RESEARCH, Issue 9 2006
    Ritabh Kumar
    Abstract Magnetic resonance imaging (MRI) is an indispensable tool for musculoskeletal imaging. The presence of metal, however, raises concerns. The potential risks are loosening and migration of the implant, heating of the metal with surrounding tissue, causing thermal damage, and artifactual distortion which compromise the diagnostic value of the procedure. The aim of this study was to test experimentally the nature and extent of the first two of these effects in orthopedic implants. The degree of ferromagnetism was evaluated by deflection studies at the portals of a 0.25 Tesla permanent magnet and 1.0 Tesla clinical MRI scanner. None of the orthopedic implants exhibited any attraction. External fixator clamps, however, showed significant ferromagnetism. The heating of implants by "worst-case" scenario imaging sequences was insignificant. Many contemporary nonferromagnetic orthopedic implants can be imaged safely. It is prudent, however, to perform ex vivo deflection studies on a duplicate implant to confirm MR compatibility. With external fixator devices exhibiting strong ferromagnetism, MRI should be avoided. With expanding indications for MRI, orthopedic implants are unlikely to limit the potential of this powerful tool. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res [source]

    Analyses of the factors for the demagnetization of permanent magnets caused by high-energy electron irradiation

    JOURNAL OF SYNCHROTRON RADIATION, Issue 3 2009
    Yoshihiro Asano
    Demagnetization owing to high-energy electron irradiation has been analyzed for permanent magnets used in insertion devices of synchrotron radiation sources, using the Monte Carlo code FLUKA. The experimental data of a thermally treated Nd2Fe14B permanent magnet with a copper or a tantalum block at electron energies ranging from 2 to 8,GeV were compared with the calculation data of the absorbed doses, photoneutron production distributions and star densities. The results indicate that low-energy photoneutrons and bremsstrahlung photons are not involved in the demagnetization process, and suggest that the star density owing to the photoneutrons is strongly correlated with the demagnetization process. [source]

    Development of a compact MRI system for trabecular bone microstructure measurements of the distal radius

    MAGNETIC RESONANCE IN MEDICINE, Issue 2 2007
    Shinya Handa
    Abstract A compact MRI system for trabecular bone (TB) microstructure measurements of the distal radius was developed using a 1.0 T permanent magnet and a compact MRI console. TB microstructure of the distal radius was clearly visualized using a three-dimensional (3D) driven equilibrium spin-echo (DESE) sequence in 23 min. The image obtained had a sufficient spatial resolution (150 ,m × 150 ,m × 500 ,m) and signal-to-noise ratio (SNR) (approximately 10) for 3D bone microstructure analysis. The system demonstrated the feasibility of using a permanent magnet compact MRI system as a clinical instrument for bone microstructure measurements of the distal radius. Magn Reson Med 58:225,229, 2007. © 2007 Wiley-Liss, Inc. [source]

    Novel highly elastic magnetic materials for dampers and seals: part II.

    POLYMERS FOR ADVANCED TECHNOLOGIES, Issue 7 2007
    Material behavior in a magnetic field
    Abstract The combination of polymers with magnetic particles displays novel and often enhanced properties compared to the traditional materials. They can open up possibilities for new technological applications. The magnetic field sensitive elastomers represent a new type of composites consisting of small particles, usually from nanometer range to micron range, dispersed in a highly elastic polymeric matrix. In this paper, we show that in the presence of built-in magnetic particles it is possible to tune the elastic modulus by an external magnetic field. We propose a phenomenological equation to describe the effect of the external magnetic field on the elastic modulus. We demonstrate the engineering potential of new materials on the examples of two devices. The first one is a new type of seals fundamentally different from those used before. In the simplest case, the sealing assembly includes a magnetoelastic strip and a permanent magnet. They attract due to the magnetic forces. This ensures that due to high elasticity of the proposed composites and good adhesion properties, the strip of magnetoelastic will adopt the shape of the surface to be sealed, this fact leading to an excellent sealing. Another straightforward application of the magnetic composites is based on their magnetic field dependent elastic modulus. Namely, we demonstrate in this paper the possible application of these materials as adjustable vibration dampers. Copyright © 2007 John Wiley & Sons, Ltd. [source]

    A PASSIVITY PLUS FLATNESS CONTROLLER FOR THE PERMANENT MAGNET STEPPER MOTOR

    ASIAN JOURNAL OF CONTROL, Issue 1 2000
    Hebertt Sira-Ramírez
    ABSTRACT A passivity based controller, in suitable combination with the flatness property of the system, is proposed for the effective feedback equilibrium to equilibrium regulation, via planned trajectory tracking, of the angular position in a permanent magnet (PM) stepper motor. The control scheme is shown to be easily modifiable as to include traditional proportional-integral-derivative (PID) feedback control actions which efficiently account for unmodeled load torque perturbations. [source]

    Magnetostatic analysis of a brushless DC motor using a two-dimensional partial differential equation solver

    COMPUTER APPLICATIONS IN ENGINEERING EDUCATION, Issue 2 2001
    A. Kostaridis
    Abstract A finite element, magnetostatic analysis, of a brushless direct current motor containing non-linear materials and permanent magnets is presented. The analysis is performed with PDEaseÔ, a low cost, two-dimensional partial differential equation solver. The descriptor file is remarkably short and easy to understand, enabling students to focus on the application and not on the finite element method. © 2001 John Wiley & Sons, Inc. Comput Appl Eng Educ 9: 93,100, 2001 [source]

    Fundamental characteristics and 3D electromagnetic analysis for magnetic levitation transporter using YBCO superconductors

    ELECTRICAL ENGINEERING IN JAPAN, Issue 2 2007
    Hiroshi Ueda
    Abstract A magnetic levitation device with two-dimensional movement, the so-called "levitating X-Y transporter," has been developed. In order to develop a working levitating X-Y transporter, it is necessary to clarify the levitation characteristics, such as the lift force, levitation height, and stability against mechanical disturbances. In this paper, we examine the lift and the restoring force experimentally and propose a new simulation program based on the three-dimensional hybrid finite and boundary element method to analyze the dynamic behavior of electromagnetic characteristics of YBCO bulk. Using the numerical simulation and experiments, we investigated a suitable arrangement of permanent magnets to enhance the levitation characteristics. We also designed a levitating transporter which can carry a load of 200 kg with a gap of 16 mm. © 2007 Wiley Periodicals, Inc. Electr Eng Jpn, 159(2): 44,54, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/eej.20220 [source]

    Design and development of a card-sized virtual keyboard using permanent magnets and hall sensors

    ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 3 2009
    Kazuyuki Demachi
    Abstract This paper proposes a method to distinguish the key-type of human fingers attached to small permanent magnets. The Hall sensors arrayed in the credit card-size area feel the distribution of the magnetic field due to the key-typing movement of the human fingers as if a keyboard exists, and the signal is analyzed using the genetic algorithm or the neural network algorithm to distinguish the typed keys. By this method, the keyboard can be miniaturized to credit card size (54 mm × 85 mm). We called this system "the virtual keyboard system." © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(3): 32,37, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10043 [source]

    Design of A New Vibration Transducer for Implantable Middle Ear Hearing Devices

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 5 2010
    Ki Woong Seong Non-member
    Abstract A new vibration transducer was developed for implantable middle ear hearing devices (IMEHDs). It comprises two permanent magnets positioned inside three coils. The transducer maximizes the interaction between the magnetic fields of the two magnets and the electrical current flowing through the coils. Further, the transducer is robust to external magnetic fields because the magnetic fields inside it are symmetrical. The frequency response was simulated by finite element analysis (FEA). The vibrational displacement of the proposed transducer is 6 dB greater than those of the differential floating mass transducer (DFMT) and the floating mass transducer (FMT). On the basis of these results, a prototype was fabricated and its frequency response was experimentally investigated and compared with simulation results. Finally, it is shown that the proposed transducer has a higher vibrational displacement than the older ones. © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

    Environmentally-friendly Aspects and Innovative Lightweight Traction System Technologies of the Shinkansen High-speed EMUs

    IEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 2 2008
    Yoshiyasu Hagiwara Member
    Abstract In 1964, the Tokaido Shinkansen marked the start of the world's first commercial service high-speed railway that operates at over 200 km/h. Since then, the Tokaido Shinkansen has demonstrated successful business and technological advancement. With the speeding-up of the Shinkansen, environmental matters such as noise and vibration have become critical issues. Measures taken to counter noise and vibration,such as weight reduction and aerodynamics,also effect global environmental measures to reduce energy consumption and CO2 emission. With the introduction of the Series 300, there was a system change of applying an AC drive system, and the lightweight body realized performance improvement over the earlier Series 0. The high-speed EMUs have readily taken advantage of technological innovation such as those achieved in electronics technology. In particular, an innovative AC drive system comprising a power converter with a GTO thyristor and asynchronous motors realized a high-performance and lightweight traction system for high-speed EMUs in the 1990s. Furthermore, recent innovations in electronics technology, such as low switching loss power devices and high-power permanent magnets, have improved the AC drive systems of the high-speed EMUs of the 21st century. This article starts out by introducing environmentally friendliness of the Shinkansen trains in terms of low energy consumption by means of traction system change, and then proceeds to describe the recent technological innovations that have given birth to lightweight traction systems, such as the Permanent Magnet Synchronous traction Motor (PMSM) and power converters with train-draft-cooling systems. The article concludes by summing up the environmentally friendly aspects of the Tokaido Shinkansen. Copyright © 2008 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source]

    Analyses of the factors for the demagnetization of permanent magnets caused by high-energy electron irradiation

    JOURNAL OF SYNCHROTRON RADIATION, Issue 3 2009
    Yoshihiro Asano
    Demagnetization owing to high-energy electron irradiation has been analyzed for permanent magnets used in insertion devices of synchrotron radiation sources, using the Monte Carlo code FLUKA. The experimental data of a thermally treated Nd2Fe14B permanent magnet with a copper or a tantalum block at electron energies ranging from 2 to 8,GeV were compared with the calculation data of the absorbed doses, photoneutron production distributions and star densities. The results indicate that low-energy photoneutrons and bremsstrahlung photons are not involved in the demagnetization process, and suggest that the star density owing to the photoneutrons is strongly correlated with the demagnetization process. [source]

    Physicochemical parameters and magnetic speciation of Iron in Nakivubo Channel and Lake Victoria waters

    LAKES & RESERVOIRS: RESEARCH AND MANAGEMENT, Issue 2 2009
    Naziriwo Betty Bbosa
    Abstract Magnetic speciation technique was used for the determination of iron species in Nakivubo Channel and Lake Victoria waters. The method consisted of a column of supported Dowex 1-X18, 20,50 US mesh (Cl) surrounded by movable permanent magnets. Dowex was supported by a porous material to permit adequate passage of the eluent through the column. In the presence of an external magnetic field, enhanced capacity for adsorption of iron III was observed. The enhanced capacity is primarily due to the magnetic field produced and ion exchange sorption mechanism. The results show that, most of the Iron in Nakivubo Channel waters is in reduced ferrous form while, in the Lake Victoria waters, it exists in the oxidized ferric form. Physicochemical parameters for the field samples are discussed in this study. Turbidity levels in catchments with substantial vegetation were significantly lower than those without. pH values up to 13 was observed for some of the point source. The physicochemical parameters along Nakivubo Channel waters were relatively higher than the Lake Victoria waters indicating slow increasing pollution load along the Nakivubo Channel. [source]

    Impeding corrosion of sintered NdFeB magnets with titanium nitride coating

    MATERIALS AND CORROSION/WERKSTOFFE UND KORROSION, Issue 2 2010
    A. Ali
    Abstract Sintered NdFeB magnets have poor corrosion resistance that renders them susceptible to corrosion in industrial and marine environments. This paper evaluates the properties of cathodic arc physical vapour deposited (CAPVD) titanium nitride coating for corrosion protection of sintered NdFeB permanent magnets. The performance of titanium nitride coating has been compared to the electrodeposited nickel,copper,nickel multilayer coating. The rates of coatings degradation in simulated marine environment were estimated with electrochemical impedance spectroscopy (EIS). Cyclic polarization was carried out to assess the pitting potential. The surface chemistry and coating morphologies were studied with scanning electron microscope (SEM). X-ray diffraction (XRD) was used for qualitative phase analyses of coatings and the substrate. It was figured out that the charge transfer resistance of CAPVD titanium nitride coating increased with exposure time. The negative rate of Rp-degradation for titanium nitride coating compared to the nickel,copper,nickel multilayer for equivalent exposure time is a unique and valuable result. Polarization results showed that ,pits re-passivation' of titanium nitride coating could be responsible for the extended corrosion protection of the NdFeB substrate. The magnetic properties remained comparable for both types of coatings. [source]

    Bulk anisotropy Nd-Fe-B/,-Fe nanocomposite permanent magnets prepared by sonochemistry and spark plasma sintering

    PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 12 2007
    Peili Niu
    Abstract NdFeB/,-Fe nanocomposite magnetic powders were prepared by sonochemical process. The powders were then submitted to a hot press and subsequent hot deformation process by spark plasma sintering (SPS) technique. Effect of ,-Fe content on structure and magnetic properties of both isotropic and anisotropic magnets was investigated. For hot pressed magnets, the remanence increases with the content of ,-Fe, while the coercive force drops simultaneously. After hot deformation, the magnets with no more than 2 vol% ,-Fe exhibit obvious anisotropic characteristic. For the magnets with more ,-Fe, however, the magnetic anisotropy disappears due to the absence of (00l) crystal texture after deformation. It is, therefore, expected that ,-Fe content plays an important role in the formation of C-axis crystal texture during hot deformation process. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

    Detection of Left Ventricle Function From a Magnetically Levitated Impeller Behavior

    ARTIFICIAL ORGANS, Issue 5 2006
    Hideo Hoshi
    Abstract:, The magnetically levitated (Mag-Lev) centrifugal rotary blood pump (CRBP) with two-degrees-of-freedom active control is promising for safe and long-term support of circulation. In this study, Mag-Lev CRBP controllability and impeller behavior were studied in the simulated heart failure circulatory model. A pneumatically driven pulsatile blood pump (Medos VAD [ventricular assist device]-54 mL) was used to simulate the left ventricle (LV). The Mag-Lev CRBP was placed between the LV apex and aortic compliance tank simulating LV assistance. The impeller behavior in five axes (x, y, z, ,, and ,) was continuously monitored using five eddy current sensors. The signals of the x - and y -axes were used for feedback active control, while the behaviors of the other three axes were passively controlled by the permanent magnets. In the static mock circuit, the impeller movement was controlled to within ±10,±20 µm in the x- and y -axes, while in the pulsatile circuit, LV pulsation was modulated in the impeller movement with the amplitude being 2,22 µm. The amplitude of impeller movement measured at 1800 rpm with the simulated failing heart (peak LV pressure [LVP] = 70 mm Hg, mean aortic pressure [AoPmean] = 55 ± 20 mm Hg, aortic flow = 2.7 L/min) was 12.6 µm, while it increased to 19.2 µm with the recovered heart (peak LVP = 122 mm Hg, AoPmean = 100 ± 20 mm Hg, aortic flow = 3.9 L/min). The impeller repeated the reciprocating movement from the center of the pump toward the outlet port with LV pulsation. Angular rotation (,, ,) was around ±0.002 rad without z -axis displacement. Power requirements ranged from 0.6 to 0.9 W. Five-axis impeller behavior and Mag-Lev controller stability were demonstrated in the pulsatile mock circuit. Noncontact drive and low power requirements were shown despite the effects of LV pulsation. The impeller position signals in the x - and y -axes reflected LV function. The Mag-Lev CRBP is effective not only for noncontact low power control of the impeller, but also for diagnosis of cardiac function noninvasively. [source]

    Magnetically Suspended Rotary Blood Pump with Radial Type Combined Motor-Bearing

    ARTIFICIAL ORGANS, Issue 6 2000
    Toru Masuzawa
    Abstract: A magnetically suspended centrifugal blood pump is being developed with a combined motor-bearing for long-term ventricular assist systems. The combined motor-bearing actively suspends a rotor in a radial direction to deal with radial force unbalance in the pump and rotates the rotor by using the electric magnetic field. Therefore, the pump has no mechanical parts such as bearings of the motor and has a long lifetime. The developed pump consists of a thin rotor with a semi open-type 6 vane impeller and a stator to suspend and rotate the rotor. The rotor has 4-pole permanent magnets on the circumferential surface. The outer diameter and the thickness of the rotor are 60 mm and 8 mm, respectively. Axial movement and tilt of the rotor are restricted by passive stability based on the thin rotor structure. Radial movements of the rotor, such as levitation in radial direction and rotation, are controlled actively by using electric magnets of the stator. The electric magnet coils to produce levitation and rotation forces are constructed on the periphery stator. The p ± 2-pole algorithm and the synchronous motor mechanism are adopted to levitate and rotate the rotor. The radial gap between the rotor and the stator is 1 mm. A closed-loop circuit filled with water was connected to the developed pump to examine the basic performance of the pump and the magnetic suspension system. Maximum rotational speed, flow rate, and head were 2,800 rpm, 11 L/min, and 270 mm Hg, respectively. The rotor with the impeller could be suspended completely during the entire pumping process. We conclude the pump with the combined motor-bearing has sufficient performance for the blood pump. [source]