局部强紧空间的Hoare空间与Smyth空间

本文主要讨论局部强紧空间的性质,特别是其Hoare空间和Smyth空间的性质,证明了T_0空间为局部强紧空间的当且仅当其Hoare空间为局部强紧空间,局部强紧空间的Smyth空间为C-空间.对于强局部紧空间,我们有类似的结论.     

广义完全分配偏序集的若干性质

广义完全分配偏序集是Menon为刻画偏序集关于其区间拓扑为紧致偏序空间时引入的,讨论了广义完全分配偏序集的一些性质。     

Structural and Magnetic Properties of Nd（Fe,Mo）12Nx Compounds Produced by Strip-Casting Method

The strip casting （SC） technique is employed to fabricate Nd（Fe,Mo）12Nx magnets. The crystallographic structure, intrinsic and permanent magnetic properties, as well as the microstruetures of the compound are investigated. There are prominent advantages for the SC Nd-Fe-Mo ailoys and their nitrides when compared with the samples prepared by the conventional casting （CC） method： （1） SC technique rebounds to the formation of the compounds crystallizing in a ThMn12-type structure. A single-phased host alloy Nd（Fe,Mo）12 can be directly prepared by strip casting without any isothermal annealing. Accordingly, lower energy cost and less rare earth demand notablely benefit the manufacture processing from a point of economizing. （2） The intrinsic magnetic properties, such as Curie temperature To, saturation magnetization Ms and anisotropy field Ha of the SC sample exceed the CC sample due to a phase forming condition with less-Mo-depended. （3） The microstructure studies also demonstrate that the SC compound contains finer grains, better-proportioned phase distribution than the CC compound. Optimized finM particles are observed aligned in their easy axis and the energy product of powder sample is up to （BH）max - 22 MGOe （176 kJ/m3）.     

Strongly Pseudoalgebraic Lattices

In the recent twenty years,the generalizations of continuous lattices have attracted aconsiderable deal of attention (see [1 -6] ) .The so-called generalized continuous lat-tices(GCL) (see[2 ] ) is one of the most successful generalizations of continuous lat-tices.In 1 990 ,Venugopalan gave the definition of pseudoalgebraic lattice and provedthat a complete lattice is a compact totally order-disconnected(Preistley) space with re-spect to the Lawson topology if and only if it is a pseadoalgeb…     

近性Heyting代数

本文在有最小元０的Ｈｅｙｔｉｎｇ代数上引入了对偶等价的（半）近性关系和（半）近性序的概念,它们是一般拓扑学中全正则空间上对偶等价的近性关系和近性序的合理推广．本文的工作弥补了Ｇｉｅｒｚ和Ｋｅｉｍｅｌ相应工作的缺陷,更正了他们的一个错误结果。     

Magnetic and Magnetocaloric Properties of Polycrystalline and Oriented Mn_(2-δ)Sn

Mn-based Heusler alloys have attracted significant research attention as half-metallic materials because of their giant magnetocr.ystalline anisotropy and magnetocaloric properties.We investigate the crystal structure and magnetic properties of polycrystalline,[101]-oriented,and[100]-oriented Mn_(2-δ) Sn prepared separately by arc melting,the Bridgeman method,and the flux method.All of these compounds crystallize in a Ni_2 In-type structure.In the Mn_(2-δ)Sn lattice,Mn atoms occupy all of the 2 a and a fraction of the 2 d sites.Site disorder exists between Mn and Sn atoms in the 2 c sites.In addition,these compounds undergo a re-entrant spin-glass-like transition at low temperatures,which is caused by frustration and randomness within the spin system.The magnetic properties of these systems depend on the crystal directions,which means that the magnetic interactions differ significantly along different directions.Furthermore,these materials exhibit a giant magnetocaloric effect near the Curie temperature.The largest value of maximum of magnetic entropy change(-△S_M)occurs perpendicular to the[100]direction.Specifically,at 252 K,maximum-△S_M is 2.91 and 3.64 J-kg~(-1)K~(-1) for a magnetic field of 5 and7 T,respectively.The working temperature span over 80 K and the relative cooling power reaches 302 J/kg for a magnetic field of 7 T,which makes the Mn_(2-δ)Sn compound a promising candidate for a magnetic refrigerator.     

强Raney偏序集

引入强Raney偏序集的概念,讨论了强Raney偏序集的一些性质,证明了强Raney偏序集为超代数偏序集,定向完备的偏序集为强Raney偏序集当且仅当它既是Raney偏序集也是A-偏序集.     

可数S_2-拟连续偏序集

作为广义可数逼近偏序集与S2-拟连续偏序集的共同推广,引入了可数S2-拟连续偏序集的概念并讨论了它的一些性质.本文的主要结果:(1)可数S2-拟连续偏序集上的可数way below关系满足插入性质;(2)可数S2-拟连续偏序集关于其上的弱σ-Scott拓扑为局部紧致的可数sober空间;(3)偏序集P为可数S2-连续偏序集当且仅当P为可数S2-交连续的可数S2-拟连续偏序集.     

Fe/Si薄膜中相干声学声子的光激发研究

本文通过抽运-探测技术, 利用飞秒激光脉冲激发并探测了Fe/Si薄膜中的高频相干声学声子. 通过经典的阻尼谐振函数, 对声学声子的动力学行为进行了拟合. 实验及拟合结果表明, 该声学声子的共振频率约为0.25 THz, 其退相时间约为12 ps, 且都与激发光的波长和能量密度无关. 声学声子的振幅随着激发光能量密度的增加而线性地增强. 临界参数12_τe-ph/T约为0.6, 表明相干声学声子的驱动力主要来源于电子热应力的贡献. 最后, 结合薄膜的厚度和质量密度, 可以得到室温下垂直于该Fe/Si薄膜表面(out of plane) 的弹性常数C_⊥约为283 GPa.