在Halbach型永磁体阵列磁场和磁化强度分布研究中,涉及永磁材料内部磁化强度(M)、磁场强度(H)和磁感应强度(B)三者的相互关系函数M(H)、M(B)和B(H).本文介绍了这些函数的典型实验特征,说明为计算获得永磁体阵列磁体内部自洽的磁场和磁化强度矢量分布,必须使用M(B)函数.强场永磁体阵列材料内部的磁场和磁化强度矢量分布无法直接被进行实验测量,不恰当地使用M(H)和B(H)函数易导致不符合实际情况的磁场和磁化强度分布状态预测.

The Halbach type hollow spherical permanent magnet arrays (HSPMA) are volume compacted, energy efficient field sources, and capable of producing multi-Tesla field in the cavity of the array, which have attracted intense interests in many practical applications. Here, we present analytical solutions of magnetic induction to the ideal HSPMA in entire space, outside of array, within the cavity of array, and in the interior of the magnet. We obtain solutions using concept of magnetic charge to solve the Poisson's and Laplace's equations for the HSPMA. Using these analytical field expressions inside the material, a scalar demagnetization function is defined to approximately indicate the regions of magnetization reversal, partial demagnetization, and inverse magnetic saturation. The analytical field solution provides deeper insight into the nature of HSPMA and offer guidance in designing optimized one. (C) 2017 Elsevier B.V. All rights reserved.

When a conventional Halbach type Hollow Cylindrical Permanent Magnet Array (HCPMA) is used to generate magnetic induction over the magnitude of coercivity mu H-0(c), some detrimental parasitic magnetic phenomena, such as the demagnetization, magnetization reversal, and vortexes of magnetization, can appear in the interior of the magnets. We present a self-consistent quantitative analysis of the magnetization and magnetic induction distributions inside the magnetic array by considering the anisotropic and nonlinear magnetization functions of the materials consisting of the array. These numeric simulations reveal novel magnetization structures resulted from the self-field of array. We demonstrate that both the field uniformity and magnetic flux in the pole gap can be modulated by partially substituting the magnets of high energy products with the soft irons and the superhard magnets. We also show how the optimized substitution parameters can be obtained for a HCPMA achieving the best field uniformity or the maximum magnetic flux. (C) 2017 Elsevier B.V. All rights reserved.

The Halbach type hollow cylindrical permanent magnet array (HCPMA) is a volume compact and energy conserved field source, which have attracted intense interests in many practical applications. Here, using the complex variable integration method based on the Biot-Savart Law (including current distributions inside the body and on the surfaces of magnet), we derive analytical field solutions to an ideal multipole HCPMA in entire space including the interior of magnet. The analytic field expression inside the array material is used to construct an analytic demagnetization function, with which we can explain the origin of demagnetization phenomena in HCPMA by taking into account an ideal magnetic hysteresis loop with finite coercivity. These analytical field expressions and demagnetization functions provide deeper insight into the nature of such permanent magnet array systems and offer guidance in designing optimized array system.

针对以往铁电制冷方式的不足提出了一种基于热开关的铁电制冷模型的新结构并进行了相关数值计算.此结构中片状铁电材料与片状热开关紧密平行排列,构成模型的基本结构.热开关分‘开’和‘关’两种可控状态,其开状态的热导率远高于关状态的热导率.系统工作时铁电材料片按奇偶位置分别加电场与去电场,每半周期交换.模拟计算涉及铁电材料单元数以及系统不同温跨下的制冷系统性能,模拟计算结果表明,在固定铁电材料单元数或系统温跨时,对于制冷效率以及制冷功率均存在最佳工作点,并且此工作点随系统温跨或铁电材料单元数变化呈规律性变化.

A simple method of analytical calculation of cooling power for the magnetic refrigerator(MR) was proposed with active magnetic regenerator(AMR),and the cooling power of the AMR was calcuated with an ideal linear temperature field.The cooling power depends on the parameters concerned was revealed.It is found that the refrigerating capacity per cycle is proportional to the square of the adiabatic temperature change induced by magnetocaloric effect(MCE) of magnetic refrigerant,or in other words,proportional to the product of adiabatic temperature change and isothermal entropy change of magnetic refrigerant.In addition,the cooling capacity is also inversely proportional to temperature span of the AMR bed.At last,heat exchange fluid with low specific heat per unit volume is preferred for the AMR.

A numerical model of a room temperature active magnetic regenerative refrigerator is presented.Cooling capacity,coefficient of performance and thermal cycle efficiency were predicted and analyzed under different working temperature spans,intensities of magnetic field and heat transfer fluids.Performances were also compared between the operation in fixed cycle and the operation in variable cycle.The result indicates that the latter is more desirable than the former.

根据主要的永磁体材料磁化性质和可能的室温磁制冷材料的磁热性质, 利用磁路定理并假定了通常使用的循环换热流体的压力差上限来计算磁制冷功率和永磁体体积之间的关系, 进而说明室温磁制冷机的制冷量的受约束情况以及实用可能性. 通过对两种典型的磁路进行的计算对比, 发现在使用高磁场时使用中空圆柱形磁聚焦方式更有效, 而在获得低于1 T的磁场时普通的救生圈环形磁路更为有效.

介绍了磁制冷效应研究进展,并回顾该效应在空间科学应用研究状况,讨论了室温磁制冷机研究进展对空间制冷研究学科的可能影响.

The recent reports by several research groups show that the vortex liquid phase of MgB-2 is the same as High Temperature Superconductivity. The most superconduct region of resistance broadening in applied fields of MgB-2 is in vortex liquid phase. we proposed a new mathematical treatment on resistance broadening in applied fields to study the effective pinning potential U-{eff} of the vortex liquid phase of MgB-2. We find that the relationship between U-{eff} and Temperature (T) is separated into two regions, one is linear dependent (U-{eff}～(T-c-T)), the other is nonlinear dependent. These findings disclosure clearly that the vortex liquid of MgB-2 has two phases, which corresponds to the discovery in HTSC YBa-2Cu-3O-{7-δ} by F. Bouquet et al (Nature, 411(2001), 448).

In this paper, the measurement equation of ac respondence about the rectangle cross-section superconductive sample with an infinite length is deduced in details, which suggests that a modification of current-density about t-{eff} should be taken into account while we study the intrinsic pinning potential of the superconductor, and the illustration of this modification is performed with MgB-2.

介绍了使用1.7 T永磁体制作室温磁制冷样机实验机的情况.在使用主动式磁蓄冷器(AMR)的循环方式下,达到了8 K的温差,说明了进一步制作较大而且更为实用的永磁体室温磁制冷样机的可行性.

C. P. Bean基于K. Mendelssohn海绵模型建立了非理想Ⅱ类超导体临界态理论, 从而形成了硬超导体电磁理论的重要基础之一.然而近年来基于涡旋动力学理论的发展,逐步形成了临界态动力学研究课题.涡旋运动导致宏观波函数的相滑移,和局域的Joule热等强烈非线性效应是形成自组织临界态物理基础.根据实验观测,磁通进入样品的前锋为线性分布,但其解析理论还在发展中.本文根据London超导理论,并结合Anderson磁通热激话理论讨论了该课题,给出了Slab样品中的电场、电流和磁通密度分布,定量解释了实验观察到的现象.

对磁制冷中的关键部件主动式磁蓄冷器(AMR)的漏热进行了数值计算,得到了漏热的组成关系,发现沿径向的热传导影响最大.如果能够有效减少AMR与磁体的接触面积或者做好径向外侧的绝热,则该系统的漏热问题将显著减少.

本文介绍一种由扁平超导样品表面垂直磁场分布反演体电流密度分布的有效方案.依据二维情形超导样品表面的磁光测量获得的局域垂直场分布,借助于磁偶极矩与磁偶极矩激发磁场的关系,利用物理问题的对称性,由求解线性方程组的共轭梯度数学方法,反演二维情形下的电流密度分布.

较为全面的综述了现有的制冷效应,详细介绍了Maxwe11方程组在制冷工程上的应用,并由此具体预言了诸如表面系统、双磁卡效应等一些新的制冷效应.

Superconductivity,magneto-thermal effect and Bose condensation developed in the low temperature physics of the 20th century are described briefly.It is pointed that these discoveries and developments will come into practical use on a large scale.All of these will give cryogenics a lot of favorable circumstances and chanlleges.

室温磁制冷在近几年取得重要进展,尤其是造出了高性能的样机和发现了巨磁热材料.但近来因为巨磁熵变发生在一级相变点,在磁熵变的计算上国际诸研究小组出现了分歧.本文对此进行了详细的讨论,给出了统一的处理方法,结果表明钆硅锗的确具有巨磁热效应.

本文以Ⅱ类超导体Abrikosov磁通结构理论为依据,采用典型的热力学方法,论证了Ⅱ类超导体在HC1相变点由Meissner态到低场混合态的相变,以及在HC2相变点由高场混合态到正常态的相变性质.我们的论证结果表明:II类超导体在HC1相变点与HC2相变点的相变均为二级相变,两相的比热差方程直接依赖相平衡曲线关系,且理论值与实验值比较的一致性约为90%.