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We have studied the magnetic and magnetocaloric properties of the Er3Co compound, which undergoes ferromagnetic ordering below the Curie temperature Tc = 13 K. It is found by fitting the isothermal magnetization curves that the Landau model is appropriate to describe the Er3Co compound. The giant magnetocaloric effect (MCE) without hysteresis loss around Tc is found to result from the second-order ferromagnetic-to-paramagnetic transition. The max- imal value of magnetic entropy change is 24.5 J/kg.K with a refrigerant capacity (RC) value of 476 J/kg for a field change of 0-5 T. Large reversible MEC and RC indicate the potentiality of Er3Co as a candidate magnetic refrigerant at low temperatures. 相似文献
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测量了 YBCO 样品在 LN_2温区及低中场的磁化曲线,得到了磁滞量△M=M^+—M^-与外场 Ba 及温度的关系.根据电磁理论的普遍关系及临界态方程,拟合了钉扎力 F_p 与磁场、温度的关系 F_p(B,T).发现存在两种类型的钉扎力:一类钉扎力很弱,在低场时起主要作用,等效于弱连接的贡献;另一类在中场和高场时起主要作用,反映了晶粒内部的钉扎性质. 相似文献
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张超武 周廉 AndreSulpice Jean-LouisSoubeyroux ChristopheVerwaerde GiaKyHoang 张平祥 卢亚峰 唐先德 《中国物理》2007,16(6):1764-1769
Through magnetization measurement with a SQUID magnetometer the heat treatment optimization of an international thermonuclear experimental reactor (ITER)-type internal-Sn Nb3Sn superconducting wire has been investigated. The irreversibility temperature T^* (H), which is mainly dependent on A15 phase composition, was obtained by a warming and cooling cycle at a fixed field. The hysteresis width △M(H) which reflects the flux pinning situation of the A15 phase is determined by the sweeping of magnetic field at a constant temperature. The results obtained from differently heat-treated samples show that the combination of T^* (H) with AM(H) measurement is very effective for optimizing the heat reaction process. The heat treatment condition of the ITER-type wire is optimized at 675℃/128 h, which results in a composition closer to stoichiometric Nb3Sn and a state with best flux pinning. 相似文献
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本文首先介绍了单芯高温超导带材交流损耗的机理,然后以SMES磁体磁滞损耗计算为例,分析了两种单芯超导带材磁滞损耗计算模型的计算结果,发现在不同场强范围内两种模型计算结果有明显的差异,并给出了计算交流损耗时两种模型的适用范围.最后简要说明了两种模型计算结果不同的原因. 相似文献
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高温超导体的交流损耗直接影响超导电力装置的运行成本和稳定性,是判断超导电力设备设计是否合理的重要特性之一.在阐述准各向同性高温超导股线结构特点的基础上,首先对准各向同性高温超导股线的交流损耗和磁滞损耗进行仿真研究,利用有限元软件Comsol Multiphysics分析了交流背景磁场下的损耗,然后在对光纤布拉格光栅(optical fiber Bragg grating,简称FBG)波长与损耗关系标定的基础上,使用光纤布拉格光栅测量交流背景磁场下的交流损耗.理论计算与实验结果相吻合,表明在工频和液氮温度下股线的交流损耗以磁滞损耗为主. 相似文献
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本文基于改进的Landau唯象相变理论,构造一个耦合的非线性常微分方程模型来模拟一维磁致伸缩材料的磁滞动态特性。模型的构造通过引入一个非凸的自由能函数来模拟磁致伸缩磁材料中不可逆的磁极化翻转与磁致应变,该自由能函数的每一个局部极小值都对应材料的一个磁化方向。通过热力学平衡条件建立能刻画磁致伸缩效应的非线性本构关系。所构造的模型成功地模拟出了磁场与弹性场之间的磁滞曲线和蝶形曲线,并采用实验结果对模型进行了验证。 相似文献
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The viscoelasticity of lipid shell and the hysteresis of subharmonic in liquid containing microbubbles 下载免费PDF全文
The viscoelasticity and subharmonic generation of a kind of lipid ultrasound contrast agent are investigated. Based on the measurement of the sound attenuation spectrum, the viscoelasticity of the lipid shell is estimated by use of an optimization method. Shear modulus GS=10MPa and shear viscosity \mu S=1.49N\cdotS/m2 are obtained. The nonlinear oscillation of the encapsulated microbubble is studied with Church's model theoretically and experimentally.
Especially, the dependence of subharmonic on the incident acoustic pressure is studied. The results reveal that the development of the subharmonic undergoes three stages, i.e. occurrence, growth and saturation, and that hysteresis appears in descending ramp insonation. 相似文献
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WUYin-Zhong LIZhen-Ya 《理论物理通讯》2002,37(2):243-246
Zero-temperature Monte Carlo simulations are used to investigate the hysteresis of a magnetic particle in a dipolar Ising model.The magnetic particle is described in a systemm of permanent dipoles,and the dipoles are located in a cubic lattice site.The effects of the shape and the size of the particle on the hysteresis loop at zero temperature are obtained.For strong exchange interactions,the shapes of magnetic hysteresis loops approach rectangle.For weak exchange interactions,the effects of the size and the shape of the particle on the loops are more remarkable than those of strong exchange interactions case.The slope of the hysteresis loop decreases with the increase of the ratio of the semi major axis to the semi minor axis of the ellipsoidal magnetic particle,and there is an increase of the slope of the hysteresis with the decrease of the size of the magnetic particle.The effects of the shape and size of the particle on the coercive force at zero temperature are also investigated. 相似文献
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