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The History of Bioelectromagnetism
Published in Shoogo Ueno, Tsukasa Shigemitsu, Bioelectromagnetism, 2022
Tsukasa Shigemitsu, Shoogo Ueno, Masamichi Kato
In the past, the magnetic field strength of a permanent magnet was too weak to demonstrate the magnetic-related phenomena of diamagnetism and paramagnetism. Around the 1980s, the magnetic field strength of a permanent magnet increased drastically due to the development of neodymium magnets. This opened a new era for the study of the magnetic properties of every material in high magnetic fields. In the presence of a neodymium magnet, the magnetic properties of diamagnetic materials can be observed with the naked eye. With neodymium magnets, apples, eggs, carbon, bismuth, etc. can be levitated. A neodymium magnet is a rare earth magnet (Nd2Fe14B) consisting mainly of neodymium, iron, and boron. It was invented by Masato Sagawa and others at Sumitomo Special Metals (later, Hitachi Metals), Japan. It is a powerful permanent magnet (Sagawa et al., 1984). At the same time, a new powerful permanent magnet was invented and reported by General Motor Corporation, USA (Croat et al., 1984). The typical research developments will be introduced as magnetic-related phenomena; levitation of diamagnetic materials and physical property changes of water and Moses effects.
Storage Technology
Published in John Watkinson, The Art of Digital Video, 2013
The focus servo moves a lens along the optical axis to keep the spot in focus. Because dynamic focus changes are largely due to warps, the focus system must have a frequency response in excess of the rotational speed. A moving-coil actuator is often used owing to the small moving mass that this permits. Figure 9.15 shows that a cylindrical magnet assembly almost identical to that of a loudspeaker can be used, coaxial with the light beam. Alternatively a moving magnet design can be used. A rare-earth magnet allows a sufficiently strong magnetic field without excessive weight.
Disks in digital video
Published in John Watkinson, An Introduction to Digital Video, 2012
The focus servo moves a lens along the optical axis in order to keep the spot in focus. Since dynamic focus-changes are largely due to warps, the focus system must have a frequency response in excess of the rotational speed. A moving-coil actuator is often used owing to the small moving mass which this permits. Figure 7.15 shows that a cylindrical magnet assembly almost identical to that of a loudspeaker can be used, coaxial with the light beam. Alternatively a moving magnet design can be used. A rare-earth magnet allows a sufficiently strong magnetic field without excessive weight.
An investigation into processing fine magnetite using a magnetic hydrocyclone
Published in Canadian Metallurgical Quarterly, 2023
Meng Zhou, Lilla A. Farkas, Ozan Kökkılıç, Raymond Langlois, Neil A. Rowson, Kristian E. Waters
Sampling took place in two sets. The first set was collected from the conventional hydrocyclone. After equilibrium was reached, samples were collected from the overflow and underflow simultaneously for approximately 15 s, with the feed rate being back calculated. For each test run, sampling was repeated twice, to decrease the margin of sampling error. After the first set of sampling was completed, the permanent magnet was attached to the cyclone. The permanent magnet used was a rare earth magnet made from neodymium–iron–boron (Nd-Fe-B), with a maximum measured field strength of 0.15 T [1]. The second set of samples was collected after the magnet was attached to the cyclone. Sampling followed the same procedure as described previously. Once the samples from the overflow and underflow had been collected, their volume was measured. The solid mass split was determined after filtering, drying, and weighing the products.
Surface properties and biocompatibility studies on bone plate by magnetorheological finishing
Published in Surface Engineering, 2022
Atul Singh Rajput, Manas Das, Sajan Kapil
The magnetic field analysis is performed to analyse the magnetic flux produced from the permanent magnet at different locations. Neodymium, iron, and boron (NdFeB) based rare-earth magnets of 15 mm diameter and 75 mm length is opted to produce the external magnetic field to stiffen the MR fluid, further used as the polishing media. NdFeB is from a rare-earth magnet family having high magnetic properties as compared with the other available permanent magnets. The aligned action of electron spin, nucleus spin, and movement of the electrons in orbit around the nucleus generates the magnetic field. However, the magnetic field generated by the permanent magnets is primarily based on their size and shape. Maxwell’s equations (Equations (1)–(4)) are used to determine the magnetic field generated through the permanent magnets.
Novel powder processing technologies for production of rare-earth permanent magnets
Published in Science and Technology of Advanced Materials, 2021
Kenta Takagi, Yusuke Hirayama, Shusuke Okada, Wataru Yamaguchi, Kimihiro Ozaki
Previous study demonstrated that it is possible to prevent surface oxidation of nanoparticles by covering part of the thermal plasma device with a glovebox to create an extremely low-oxygen atmosphere [54]. Figure 10 shows an example of the rare-earth magnet nanoparticles synthesized by this method, in this case, Sm-Co alloy nanoparticles having an average particle size of 70 nm. In addition, nanoparticles of Y-Fe, Nd-Fe, and Sm-Fe alloys have been also produced. In particular, synthesis of metastable phase nanoparticles of a TbCu7 type alloy has been confirmed [55].