Frictional Effects in Thin 3He Films

The recent high-precision torsional oscillator experiments of Casey et al. involving thin films of normal liquid ³He showed that the film decouples from the substrate with a time constant which is proportional to T ⁻¹ where T is the absolute temperature. We interpret this experiment by adapting a theory due to Meyerovich which was developed for dilute ³He-⁴He mixtures flowing between two relatively smooth plates. The analysis of the experiment confirms the central idea that varies as T ⁻¹. The variation of with film thickness, d, is affected by the change in the shape of the free surface of the film, due to van der Waals forces, as the film becomes thinner.     

降低电磁纯铁冷轧薄板矫顽力的研究

就铝合量和冷轧变形量对电磁纯铁冷轧板矫顽力(Hc)的影响结合生产实际进行了研究并在生产实残中取得较好效果。     

On Larkin-Imry-Ma State of 3He-A in Aerogel

Superfluid ³He-A shares the properties of spin nematic and chiral orbital ferromagnet. Its order parameter is characterized by two vectors and . This doubly anisotropic superfluid, when it is confined in aerogel, represents the most interesting example of a system with continuous symmetry in the presence of random anisotropy disorder. We discuss the Larkin-Imry-Ma state, which is characterized by the short-range orientational order of the vector , while the long-range orientational order is destroyed by the collective action of the randomly oriented aerogel strings. On the other hand, sufficiently large regular anisotropy produced either by the deformation of the aerogel or by applied superflow suppresses the Larkin-Imry-Ma effect leading to the uniform orientation of   . The interplay of regular and random anisotropy allows us to study many different effects.      

Quantum Fingering of the Inverted Liquid-Crystal 4He Interface in the Field of Gravity

The simplest example of fingering occurs when a heavier liquid occupies the half-space above a lighter one. The fingers of the heavier liquid driven by gravity grow down, displacing the lighter liquid upward. The fingering of the superfluid phase into the ⁴He crystal facet below its roughening transition temperature can provide us an example of macroscopic quantum nucleation phenomena. Due to cusp-like singularity in the surface tension as a function of the facet orientation the crystal facet has a relative stability and its fingering is accompanied by overcoming some critical nucleation barrier. The barrier height is proportional to the square of the facet step energy and depends on a ratio of the facet size to the capillary length. At sufficiently low temperatures the thermal activation mechanism for the interface fingering is replaced with the quantum one associated with the penetration through the nucleation barrier.      

Long-Range Order in the A-like Phase of Superfluid 3He in Aerogel

A mutual action of the random anisotropy brought in the superfluid ³He by aerogel and of the global anisotropy caused by its deformation is considered. Strong global anisotropy tends to suppress fluctuations of orientation of the order parameter and stabilizes ABM order parameter. In a limit of vanishing anisotropy fluctuations of ABM order parameter became critical. It is argued that still in a region of small fluctuations the order parameter changes its form to be less sensitive to the random anisotropy. For a favorable landscape of the free energy of superfluid ³He the fluctuations remain small even in a limit of vanishing global anisotropy and the long-range order is maintained.      

Study of the damage produced in 6H-SiC by He irradiation

Lattice damage and evolution in 6H-SiC under He⁺ ion irradiation have been investigated by the combination of Rutherford backscattering in channeling geometry (RBS/C), Raman spectroscopy, UV–visible spectroscopy and transmission electron microscopy (TEM). 6H-SiC wafers were irradiated with He ions at a fluence of 3 × 10¹⁶ He⁺cm⁻² at 600 K. Post-irradiation, the samples were annealed in vacuum at different temperatures from 873 K to 1473 K for isochronal annealing (30 min). Thermally annealed He irradiated 6H-SiC exhibited an increase in damage or reverse annealing behavior in the damage peak region. The reverse annealing effect was found due to the nucleation and growth of He bubbles. This finding was consistent with the TEM observation. The thermal annealing brought some recovery of lattice defects and therefore the intensities of Raman peaks increased and the absorption coefficient decreased with increasing annealing temperature. The intensity of Raman peak at 789 cm⁻¹ as a function of annealing temperature was fitted in terms of a thermally activated process which yielded activation energy of 0.172 ± 0.003 eV.     

苏里格气田苏14井区盒8段层序地层格架中的沉积微相与砂体分布规律研究

鄂尔多斯盆地苏里格气田苏14井区上二叠统盒8段沉积特征与4个中期基准面旋回密切相关,盒8下亚段的MSC1、MSC2中期旋回主要发育基准面上升半旋回,为辫状河沉积;盒8上亚段2小层的MSC3旋回东部为上升半旋回,西部为非对称旋回,沉积相呈"东辫西曲"的格局;盒8上亚段1小层的MSC4旋回为对称旋回,主要发育曲流河沉积。这种沉积格局进而影响砂体分布,MSC1旋回和MSC2旋回砂体规模大,厚度大,横向连续性好;MSC3旋回东部砂体规模较西部大,横向连续性较好;MSC4砂体规模减小,厚度较薄,多呈孤立状,横向连续性差。     

颓废与拯救--何其芳文学精神的一个主题

从颓废、独语、拯救三个主题分析何其芳文学精神,阐释作为知识分子的诗人何其芳在文学上的精神拯救问题,试图进行精神层面的思考和把握.     

明代中医药海外交流中的互融互通

作为近现代史上中医药对外交流互摄互融的巅峰时期,明代中国在药材贸易、医药典籍、医疗技术的中外交流方面空前繁荣。由于朝贡体系、郑和下西洋、地理大发现、民间海外贸易等重要交流通路的形成,中医药的海外交流版图扩张至东亚、南亚、西欧。在互通互融的背景下,中医药学得以依照各国文明强盛程度,与各国本土医药体系进行交流与碰撞。故试图从不同交流通路和地理维度的视角下,窥探中医药在海外交流的过程中,中医药体系和各国医药体系的相互影响。