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超导块材和永磁铁相互作用形成悬浮系统。讨论了对超导块材进行网格划分的方法,利用矢量电位法建立了Nd-FeB永磁铁和超导体相互作用的电磁场数学方程。利用伽辽金法形成有限元线性方程组。求解过程中采用Kim模型作为迭代条件,解出超导体电流密度分布,并进行受力分析。 相似文献
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在高温超导磁悬浮系统中,超导体和应用外磁场之间的电磁作用比较复杂。通常,任何测试过程对高温超导磁悬浮系统中相互作用力(悬浮力和导向力)结果都有影响。为了能够得到准确的测试结果,文中研究了测试过程对导向力和悬浮力测试结果的影响,发现高温超导磁悬浮系统中存在的磁历史效应导致了这种影响的存在是必然的,而且是交叉影响作用。实验数据进一步指出,在实际的测试过程中必须根据具体的运动路径来选择悬浮力和导向力的测试过程和顺序,以尽可能地减小两者之间的负面影响。根据不同的测试目的,文中也推荐了对应合理的测试方法。 相似文献
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Jun Zhou Xing-Yi Zhang You-He Zhou 《Physica C: Superconductivity and its Applications》2010,470(5-6):336-339
Using a modified Gifford–McMahon refrigerator to cool the cylindrical bulk YBaCuO superconductor within the region of 100–10 K, and using an updated high-temperature superconductor (HTS) maglev measurement system, the levitation force and its time relaxation at different temperatures between a YBaCuO bulk superconductor and a permanent magnet (PM) have been measured under zero-field cooling. It is found that decrease the cooling temperature of HTS can decrease the hysteresis of magnetization and increase the maximum levitation force of each hysteresis loop. For the relaxation of levitation force, if the temperature is continually lowered to 10 K after the relaxation measurement at given cooling temperature is performed for 600 s, the levitation force will continue to decrease sharply with the lowering of temperature even though it will get stable if the temperature is not lowered. Our results shown in this work are a benefit to the understanding of levitation systems. 相似文献
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基于Kim临界态模型,通过考虑超导块材内部屏蔽电流的穿透历史过程,讨论了场冷条件下临界电流密度对高温超导悬浮系统磁悬浮排斥力和吸引力的影响.结果显示:最大超导磁悬浮排斥力和吸引力均随临界电流密度的增加呈指数关系增加,并趋于饱和;场冷条件下的磁悬浮力回滞能量损耗远高于零场冷情况;存在一个磁悬浮力比率κ,κ值对于评价大电流... 相似文献
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利用矢量电位法建立了NdFeB永磁铁和超导体相互作用的电磁场数学模型方程。在求解过程中采用磁通流动蠕动模型,通过伽辽金有限元离散,解出超导体电流密度分布,计算磁悬浮力并分析磁悬浮力磁滞性质。 相似文献
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Qiong-Gui Lin 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,54(1):27-36
The interaction between a general magnetic source and a
long type-II superconducting cylinder in the Meissner or mixed state
is studied within the London theory. We first study the Meissner
state and solve the Maxwell–London equations when the source is a
magnetic monopole located at an arbitrary position. Then the field
and supercurrent for a more complicated magnetic charge distribution
can be obtained by superposition. A magnetic point dipole with
arbitrary direction is studied in detail. It turns out that the
levitation force on the dipole contains in general an angular as well
as a radial component. By integration we obtain the field and
supercurrent when the source is a two-dimensional monopole (a
magnetically charged long thread along the axial direction), from
which the results for a two-dimensional point dipole easily follow.
In the latter case the levitation force points in the radial
direction regardless of the orientation of the dipole. The case for a
current carrying long straight wire parallel to the cylindrical axis
is solved separately. The limit of ideal Meissner state is discussed
in most cases. The case of mixed state is discussed briefly. It turns
out that vortex lines along the axial direction and vortex rings
concentric with the cylinder have no effect outside the cylinder and
the levitation forces remain the same as in the case of the Meissner
state. 相似文献
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R. Parthasarathy M.M. Lakshmi V. Seshubai 《Physica C: Superconductivity and its Applications》2011,471(13-14):395-399
Time relaxation behavior of levitation force has been studied in IGP bulk YBCO/Ag superconductor using levitation force measurements as these measurements throw light on the magnetic relaxation in superconductors and the underlying vortex dynamics, pinning mechanisms and the nature of pinning forces. The measurements have revealed a hitherto unknown near-oscillatory relaxation of the levitation force with varying magnetic field. This kind of behavior is found to be more pronounced at smaller gap distances between the permanent magnet and the superconductor. A switch-type polarity bistable equilibrium model for the supercurrent structure has been proposed based on the understanding that even the permanent magnet gets magnetized in the presence of the superconductor, which has also been verified and reported here. This model satisfactorily explains the observed oscillatory behavior of relaxation rates. 相似文献
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This paper undertakes a nonlinear analysis of a model for a maglev system with time-delayed feedback. Using linear analysis, we determine constraints on the feedback control gains and the time delay which ensure stability of the maglev system. We then show that a Hopf bifurcation occurs at the linear stability boundary. To gain insight into the periodic motion which arises from the Hopf bifurcation, we use the method of multiple scales on the nonlinear model. This analysis shows that for practical operating ranges, the maglev system undergoes both subcritical and supercritical bifurcations, which give rise to unstable and stable limit cycles respectively. Numerical simulations confirm the theoretical results and indicate that unstable limit cycles may coexist with the stable equilibrium state. This means that large enough perturbations may cause instability in the system even if the feedback gains are such that the linear theory predicts that the equilibrium state is stable. 相似文献
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Longcai Zhang Suyu Wang Jiasu Wang 《Physica C: Superconductivity and its Applications》2009,469(13):685-688
Superconducting maglev vehicle was one of the most promising applications of HTS bulks. In such a system, the HTS bulks were always exposed to AC external magnetic field, which was generated by the inhomogeneous surface magnetic field of the NdFeB guideway. In our previous work, it was observed that the guidance force of the YBCO bulk over the NdFdB guideway used in the high-temperature superconducting maglev vehicle system was decayed by the application of the AC external magnetic field. In this paper, we adopted a method to suppress the decay by altering the field–cooled height of the bulk. From the experimental results, it was found that the decay rate of the guidance force was smaller at lower field–cooled height. So we could suppress the guidance force decay of HTS bulk exposed to AC external magnetic field perturbation in the maglev vehicle system by reducing the field–cooled height of the bulk. Furthermore, all the experimental results in this paper were explained based on Bean critical-state model. 相似文献
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Y. Q. Zhang J. B. Xu 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2011,63(3):483-488
By making use of the dynamical algebraic method we investigate a quantum system consisting of superconducting qubits interacting
with data buses, where the qubits are driven by time-dependent electromagnetic field and obtain an explicit expression of
time evolution operator. Furthermore, we explore the entanglement dynamics and the influence of the time-dependent electromagnetic
field and the initial state on the entanglement sudden death and birth for the system. It is shown that the entanglement between
the qubit and bus as well as the entanglement sudden death and birth can be controlled by the time-dependent electromagnetic
field. 相似文献
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This study develops a computational model of the dynamic characteristics of the actively controlled, magnetically levitated (maglev) system moving on a flexible guideway. The 5-dof (degree-of-freedom) vehicle model, the modeling of the EMS (electromagnetic suspension), guideway, and guideway irregularity are described, respectively. In this sense, the dynamic response of a coupled vehicle and guideway system is investigated with different vehicle speeds and masses. Furthermore, the formulation of SMC (sliding mode control) based on the Kalman filter is addressed for the control of the dynamic response of the maglev system for various prescribed running speeds. For numerical simulation, the Runge-Kutta method is used to solve the state-space equation, which includes information about the vehicle, guideway and controller. The results reveal that both the air gap fluctuation and the cabin CG (center of gravity) vertical acceleration are strongly affected by the vehicle speed and guideway irregularity, but only slightly affected by the vehicle mass. Moreover, SMC based on the Kalman filter considerably reduces the air gap fluctuation and cabin CG vertical acceleration responses, and the efficiency of the adopted control methodology is demonstrated even at higher critical speed conditions. 相似文献
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A. N. Terentiev H. J. Lee C. -J. Kim G. W. Hong 《Physica C: Superconductivity and its Applications》1997,290(3-4):291-296
By measuring the quality factor of the mechanical oscillator with an attached magnet we investigated the amplitude dependence of the energy loss in a permanent magnet-YBCO superconductor system. When a non-conducting ferrite magnet is used the energy loss is proportional to the amplitude to the 2.79 power. This value is close to the value of 3 expected for the hysteretic motion of flux lines from the Bean model. When a conducting magnet is used the exponent decreased to the value of 2.5. This reflects the contribution of eddy current dissipation in a conducting magnet to the overall loss. We identified a novel mechanism of ac loss in the magnet-superconductor system. According to this mechanism the eddy current in a magnet is induced by the ac field generated by the ac supercurrent in response to the motion of a magnet. This mechanism would take place in a rotary bearing if circumferential inhomogeneity of the rotor magnetization occurred. 相似文献