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本给出了三种提高YBCO块材在外磁场中悬浮力的方法.第一种方法是增强外磁场,对于此方法,本研究了一块直径为30mm的圆柱状YBCO块材分别在圆柱状NdFeB永磁体和NdFeB永磁导轨上的悬浮力.测量结果表明在77K温度下YBCO块在圆柱状NdFeB永磁体上的最大悬浮力为50N,在NdFeB永磁导轨上的最大悬浮力为103.ON.第二种方法是提高YBCO块材自身的性能,包括临界电流密度、俘获磁通和块材尺寸,对于此方法,本仅研究了块材尺寸对悬浮力的影响.三块直径分别为30mm、35mm、40mm的圆柱状YBC0块材在NdFeB永磁导轨上的悬浮力被测量,77K温度下5mm悬浮间距时的悬浮力分别为103.ON、134.5N、175.ON.第三方法是将YBCO块材变成准永久磁体,此种情况下,直径为40mm的圆柱状YBCO块材在77K温度下5mm悬浮间距时的悬浮力高达218.3N. 相似文献
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方俊 《中国科学B辑(英文版)》1991,(1)
In the linear inversion of the radial variation of the parameters of the Earth by usingthe observed frequencies of various normal modes of free oscillation of the earth, it is neces-sary to know the values of the kernels of the parameters ρ, μ and λ. This paper describesthe methods of the derivation of the formulas of these kernels. This is the first part of thepaper in which only the toroidal oscillations are considered. They are much simpler thanthose of the spheroidal ones, that we will consider in the second part of the paper. The data of the two types of oscillations are equally important in the solution of theinversion problem, and should be employed simultaneously, and we know that the toroidaloscillations are much simpler than the spheroidal ones, it seems wise to divide the whole programof the inversion problem into steps: first, by employing the toroidal data to correct the twoparameters ρ and μ in the mantle, then by using the spheroidal data to correct the remain-ing parameters, i.e. th 相似文献
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ABSTRACT Superporous hydrogels, hydrogels with pore sizes in the range of 100 μm and larger, were synthesized using N-isopropyl-acrylamide (NIPAM) and acrylamide (AM). The superporous hydrogels were synthesized by crosslinking polymerization of monomers in the presence of gas bubbles. The pores of superporous hydrogels were connected to each other to form open capillary channels, which provided fast response to the changes in the environmental temperature. Upon increase in temperature from 10°C to 65°C, the superporous hydrogel made from a monomer solution of NIPAM:AM = 9:1 shrank from the fully swollen state (volume of 36 cm3) to the fully collapsed state (volume of 6.5 cm3) in 72±14 sec. When the temperature was changed back to 10°C, the superporous hydrogel swelled to 36 cm3 in 78±15 sec. This deswelling-swelling cycle was repeated many times without changes in the thermo-reversible property of the superporous hydrogel. The response time of the superporous hydrogels was thousand times faster than that of conventional hydrogels. The fast response of the superporous hydrogels is due to the rapid uptake or exclusion of water molecules through the extensive capillary channels. Because superporous hydrogels still maintain the open capillary structure even after drying, the dried superporous hydrogels can also swell to the equilibrium swelling state within minutes. These fast responsive hydrogels can find many pharmaceutical and medical applications. 相似文献
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离子型共聚单体参与下的全氟丙烯酸酯无皂乳液共聚 总被引:4,自引:0,他引:4
离子型共聚单体参与下的全氟丙烯酸酯无皂乳液共聚;全氟烷基丙烯酸酯;无皂乳液;离子型共聚单体 相似文献
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