共查询到19条相似文献,搜索用时 187 毫秒
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传统核磁共振仪器多采用封闭式磁体结构,导致仪器开放性和便携性差,制约其应用范围。为解决上述问题,该文基于电磁场理论,利用二阶有限元方法,研究半环形Halbach磁体的结构设计方法,分析磁块几何结构和尺寸等参数对Halbach磁体产生的中心场强、横向均匀度和纵向梯度的影响。验证该磁体结构无需增加线圈,即可产生核磁共振实验所需的横向均匀纵向梯度分布的磁场。优化后的单边Halbach磁体结构为:磁块尺寸为0.5 m×0.095 m×0.095 m、磁体结构半径为0.63 m,在50 cm×50 cm区域得到中心场强为0.020 9 T,不均匀度为3.085×10~(-4),梯度为0.739 mT/cm的磁场。 相似文献
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在脉冲强磁体设计中,磁应力是我们面临的最大挑战,当磁场强度达到100T时,磁体绕组中的磁应力高达4GPa,这是目前任何实用导体材料都无法承受的,因此,脉冲强磁体的发展在很大程度上取决于磁应力的解决情况.文章从提高导体材料机械强度的角度出发,介绍了目前各种导体材料的加工过程和技术参数,包括铜、铜宏复合导体材料、铜微复合导体材料、多层绞线复合导体材料等. 相似文献
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烧结钕铁硼磁体因具有优异的磁性能、较好的机械加工性和低成本等优势而被广泛应用在现代工业和电子技术领域。然而,随着科技的不断进步,对烧结钕铁硼磁体的磁性能提出了更高要求,高剩磁、高矫顽力、高磁能积磁体成为今后发展的重要趋势。磁体组织结构决定了磁体性能,磁体组织结构又与磁体成分密切相关。成分优化是改善烧结钕铁硼磁体磁性能的有效途径。本文在分析烧结钕铁硼磁体组织结构的基础上,详细梳理了近几十年来烧结钕铁硼磁体组元元素替代和掺杂的研究成果。在此基础上,指出了元素替代和掺杂在改善烧结钕铁硼磁体磁性能中存在的问题及今后的发展方向,为进一步提高烧结钕铁硼磁体磁性能提供理论参考。 相似文献
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在强磁体结构中,电磁力是主要载荷。由于磁场计算和结构分析属不同学科,这两部分研究一般都是孤立地、分别进行的。本文指出了这样研究的弊病,提出了磁场和应力同步分析的方法。并以中国HL-1托卡马克磁体为例,采用有限元应力分析和三维磁场计算同步进行的方法,得到了托卡马克环向场线圈的磁体力、应力和变形分布。 相似文献
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郭洪臣 《中国新技术新产品》2009,(21):1-3
<正>(上接20期)八、磁动力机的开关与调速开关与调速是一个原理,用同一套机构完成的。原理是用磁力的"同性相斥"的特性即以磁体对应面积多少和对应距离大小而决定。磁动机力量的大小决定于磁体大小和块数的多少所构成同磁极相对应的距离远近和面积多少。磁体大并块数多,相互对应面积就多,两磁距离近力量就大,反之则小。如图: 相似文献
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Nuria Del-Valle Alvaro Sanchez Carles Navau Du-Xing Chen 《Journal of Low Temperature Physics》2011,162(1-2):62-71
The characteristics of the permanent magnets composing the guideway in superconducting magnetic levitation devices are very important for their performance in terms of levitation force and stability. From a model based on minimizing the magnetic energy in the superconductor and considering realistic parameters of actual maglev devices, we calculate the levitation and guidance forces and stability arising from both conventional arrangements and recently proposed Halbach-like arrangements. When a comparison is carefully made under similar conditions, we conclude that not always complicated arrangements based on Halbach arrays bring significant improvements with respect to some simpler arrangements that also provide large force. These results may help improving the design of actual maglev devices. 相似文献
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《IEEE transactions on magnetics》2008,44(10):2361-2366
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The lateral reversible region of the high-T c superconductor (HTSC) bulk YBCO above a permanent magnet guideway (PMG) is investigated experimentally in this study. The dependence of the lateral reversible region upon selected parameters, such as Field Cooling Height (FH), Working Height (WH), and magnetic field structure, is studied. Results show that the lateral reversible region of the HTSC bulk is not only proportional to the magnitude of the guidance force or guide-force hysteresis, but closely related to the external applied magnetic field structure, FH, WH, and the size and shape of the HTSC bulk. A conclusion that the lateral reversible region of an HTSC bulk over the single peak symmetrical PMG prior to multipeak Halbach PMG is drawn. The results may be helpful to the design and optimization of maglev systems composed of a permanent magnet guideway and HTSCs. 相似文献
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为实现多方向环境能量收集,设计球形电磁式振动能量采集器。基于二维Halbach阵列设计的球面Halbach永磁阵列,较传统永磁阵列能提高线圈中磁链变化梯度,从而提高结构输出性能;建立数学解析模型,据解析结果对模型各参数进行优化;对该模型进行有限元仿真分析及实验性能测试。结果表明,该模型能有效响应空间任意方向振动,进而转化为电能;外部激励为10 Hz、激励为水平方向、负载阻值50 Ω时,该球形振动能量采集器输出电能达最大,单个线圈中最大负载功率可达0.8 mW。 相似文献
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3-D Magnetic Field and Torque Analysis of a Novel Halbach Array Permanent-Magnet Spherical Motor 总被引:1,自引:0,他引:1
《IEEE transactions on magnetics》2008,44(8):2016-2020
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磁悬浮运动平台的磁场分析及优化设计 总被引:3,自引:0,他引:3
研制了一种新型磁悬浮平台,该平台定子采用无铁心式的克莱姆绕组,消除了固有齿槽效应,动子采用Halbach 磁阵列结构方式,由于平台输出推力与悬浮的稳定性主要与其气隙磁场的分布情况有直接关系,因此提高气隙磁场的正弦分布是改善其工作特性的难点和重点. 为了改善气隙磁场的分布问题,提出了一个优化磁场分布的目标函数,并采用步长加速法对平台磁场进行了优化设计,大大降低了磁场谐波分量,改善了气隙磁场分布状态. 将优化结果运用到实际的平台中,对该运动平台进行了阶跃响应实验,实验结果表明满足平台需要达到纳米级精度的要求. 相似文献
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Yujie Qin Yiyun Lu Suyu Wang Jiasu Wang 《Journal of Superconductivity and Novel Magnetism》2009,22(5):511-516
The zero-field cooling levitation force relaxation of the YBCO bulk above two types of NdFeB guideways, which were used in
the high-temperature superconducting maglev vehicle system, was studied experimentally when the bulk moved towards the guideways
at different speeds. In this experiment, a sample with the diameter of 50 mm and thickness of 15 mm was used; the time range
in the relaxation measurements was from 0 s to 200 s. As a result, a nearly linear logarithmic decay of the levitation forces
with time was observed. It was found that the influence of the approaching speeds on the levitation force relaxation is different,
and that the levitation force decay is closely related to the guideway structures. Based on the monopole peak PMG, the approaching
speeds will influence more the levitation force decay than the multipole Halbach. So the maglev vehicle above mutipole Halbach
structure PMG will work more stably than that above the monopole peak PMG.
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A bipolar permanent magnetic guideway (PMG) has a unique magnetic field distribution profile which may introduce a better levitation performance and stability to the high- $T_{c}$ superconducting (HTS) maglev system. The dynamic vibration properties of multiple YBCO bulks arranged into different arrays positioned above a bipolar PMG and free to levitate were investigated. The acceleration and resonance frequencies were experimentally measured, and the stiffness and damping coefficients were evaluated for dynamic stability. Results indicate that the levitation stiffness is closely related to the field-cooling-height and sample positioning. The damping ratio was found to be low and nonlinear for the Halbach bipolar HTS-PMG system. 相似文献
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Lu Liu Jiasu Wang Suyu Wang Lulin Wang Jing Li 《Journal of Low Temperature Physics》2009,157(1-2):67-72
The permanent magnetic guideway (PMG) composed of permanent magnet (PM) and steel is developed under flux concentration principle, which is the crucial component of high-temperature superconducting (HTS) maglev vehicle system. Optimum PMG design is an effective way to increase levitation force and associated stiffness for improving the load capability of HTS maglev vehicle. In order to realize higher vertical field component B z in upper surface, three PMG demonstrators with three different forms of flux concentrator are fabricated with same volume of magnet. The levitation performances of onboard HTS bulks array over them are studied. The experimental results indicate that the PMG with a permanent magnet as the flux concentrator would produce biggest levitation force, levitation stiffness and trapped flux when interacting with HTS superconductor. 相似文献