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[en] In contrast to the interaction between two magnets with opposite magnetization directions, the interaction between a permanent magnet and a superconductor can be stable and result in magnetic levitation. This property can be exploited for the development of high velocity rotating bearings with no mechanical contacts and for the development of levitated trains. In this review, we focus on this latter application. After a brief description of the other techniques developed for levitating trains and the resulting achievements, we describe the magnet–superconductor interaction and recall the achievements in this field. We then give insights into the properties of the employed magnets and arrangement of magnets and we detail the characteristics and the fabrication processes of the most frequently used superconductors. Focusing on physics, we detail the procedures generally used for measuring the vertical (levitation) and the lateral (guidance) forces in magnetic levitation and the results obtained from experiments. We detail and give a critical review of the various models proposed for reproducing the force measurements. In the conclusion we discuss the possible future developments of the technology. (topical review)
[en] Highlights: • Coasting time was investigated from the point-view of HTS flywheel applications. • The coasting time of aligned growth section boundary pattern (AGSBP) is shorter than that of MGSBP. • The electric magnetic drag force with AGSBP is larger than that of MGSBP. • This result may also exist in the maglev guideline when the maglev train stops freely. - Abstract: High-temperature superconductors (HTSCs) array with aligned growth section boundary (GSB) pattern (AGSBP) exhibits larger levitation force and suppression of levitation force decay above a permanent magnet guideway (PMG) compared with misaligned GSB pattern (MGSBP) has been studied in maglev train application (Zheng et al., 2013). This result maybe helpful and support a new way for the HTS bearing design for flywheel systems. So, in this paper, we further examine this growth anisotropy effect on the maglev performance of flywheel system. Levitation force and coasting time were investigated from the point-view of HTS flywheel applications. The GS/GSB alignment of AGSBP bulk HTSCs produces larger levitation force than that of MGSBP, but the coasting time is shorter than that of MGSBP, that is to say, the electric magnetic drag force with AGSBP is larger than that of MGSBP. This result may also exist in the maglev guideline when the maglev train stops freely
[en] The authors begin this book with a systematic overview of superconductivity, superconducting materials, magnetic levitation, and superconducting magnetic levitation - the prerequisites to understand the latter part of the book - that forms a solid foundation for further study in High Temperature Superconducting Magnetic Levitation (HTS Maglev). This book presents our research progress on HTS Maglev at Applied Superconductivity Laboratory (ASCLab) of Southwest Jiaotong University (SWJTU), China, with an emphasis on the findings that led to the world's first manned HTS Maglev test vehicle ''Century''. The book provides a detailed description on our previous work at ASCLab including the designing of the HTS Maglev test and measurement method as well as the apparatus, building ''Century'', developing the HTS Maglev numerical simulation system, and making new progress on HTS Maglev. The final parts of this book discuss research and prototyping efforts at ASCLab in several adjacent fi elds including HTS Maglev bearing, Flywheel Energy Storage System (FESS) and HTS maglev launch technology. We hope this book becomes a valuable source for researchers and engineers working in the fascinating field of HTS Maglev science and engineering.
[en] We use magnetic levitation and a variable-separation dual optical plug to obtain clear spatial interference between two condensates axially separated by up to 0.25 mm - the largest separation observed with this kind of interferometer. Clear planar fringes are observed using standard (i.e., nontomographic) resonant absorption imaging. The effect of a weak inverted parabola potential on fringe separation is observed and agrees well with theory.
[en] A phased array of ultrasonic emitters for acoustic levitation has been developed. The array is controlled by a multichannel signal generator. The generator allows you to create 64 channels of independent signals with controlled phase. The possibility of connecting of 4 arrays of emitters, each of the 320 elements. The possibility of providing levitation of foam particles in the field of two oppositely directed arrays was experimentally shown. (paper)
[en] Force is one of the most basic mechanical quantities and is usually measured using force transducers. However, the dynamic calibration method of force transducers has not been established. It's due to two major problems concerning material testing. On the one hand, it is difficult to evaluate the uncertainty of the measured value of the varying force. On the other hand, it is difficult to evaluate the uncertainty of the time at which the varying force is measured. According to this, ''Levitation Mass Method'' (LMM) was proposed by the author. In this method, the inertial force of a mass which levitated using a pneumatic linear bearing is used as the reference force applied to the objects being tested, such as force transducers, materials and structures. As the inertial force of the levitated mass is measured using an optical interferometer. In the LMM, only the motion-induced time varying beat frequency is measured during the measurement, and all the other quantities, such as velocity, position, acceleration and force, are numerically calculated afterwards. The results between the obtained quantities are in good synchronism. In addition, force is directly calculated according to its definition, that is, the product of mass and acceleration. In this paper, the recent achievement and the future prospects on the method for precision mass and force measurement, the levitation mass method (LMM), are reviewed. The three typical applications of the LMM, the dynamic force calibration, the micro force material tester and the space scale, are reviewed. (author)
[en] By taking into account thermic emission current from hot dust surface, the problem involved in dust charging and levitation of dust grains in plasma sheath has been researched. The results are compared to that without including thermal emission current while the system parameters are same. It is found that the thermal emission current has played a significant role on modifying the dust charging and balance levitations. Both of the charging numbers of dust and the dust radius in balance are dramatically reduced. The stability of dust levitation is also analyzed and discussed.
[en] This paper reports on Canadian studies of superconducting magnetic levitation and variable-speed linear synchronous motor propulsion for high-speed inter-city guided ground transport. Levitation is obtained by the interaction of vehicle-mounted superconducting magnets and the eddy currents induced in aluminium strip conductors on the guideway. Non-contact propulsion by linear synchronous motor (LSM) is obtained by using vehicle-borne superconducting magnets and powered guideway coils. A suggested guidance scheme uses a flat guideway with 'null-flux' loops overlying the LSM windings. The propulsion magnets interact with the loops and the edges of the levitation strips to provide lateral stabilization. The test facility is a 7.6m wheel, rotating with a peripheral speed of 33m/s. (author)
[en] This patent describes a gradiometer having a sensitive axis for detecting a gravity gradient along the sensitive axis, comprising: a pair of accelerometers having respective sensitive axes; each accelerometer including a proof mass having a pair of hollowed out annular portions; each proof mass having at least one sensing coil arranged adjacent a bottom-side surface of the respective proof mass in one of the hollowed out portions and a levitation coil arranged adjacent a second bottom-side surface of the respective proof mass in the other hollowed out portion, at least one sensing coil and the levitation coil thus being located on the same side of the respective proof mass in relation to the direction of an external force exerted on the gradiometer thereby to compensate for temperature induced changes in magnetic field penetration into the respective proof mass; at least one first superconducting circuit in which the sensing coils of the accelerometers are interconnected and in which a first persistent current flows, the first circuit having an output indicative of a gravity gradient along the sensitive axis of the gradiometer
[en] We present an experimental study of the relaxation of vertical and horizontal force components in an unsymmetrical high-temperature superconducting levitation system, with different initial cooling processes, after fixing the levitated body statically in a given position. It was found that the values of the relaxation measurements of the levitation force and lateral force remained constant or increased with time after vertical and horizontal traverses. The phenomenon has been theoretically described based on the Bean model and the thermally activated flux creep theory. The criterion developed in the present work is considered to be suitable for providing qualitative predictions of the relaxation properties in the levitation force and lateral force.