Improved Pinning Center Morphology in HTS with Order－of－Magnitude Increase in Jc and Bpin Compared to Columnar Pinning

The motivation for continuous columnar pinning centers has been to provide maximum Upin It has been assumed that this provides the best Jc and Bpin. Limitations on Jc and Bpin, observed for columnar pinning have been attributed to degradation of the order parameter and Tc. We examine columnar pinning by ionic damage and cooclude instead that geometrical effects of columnar pinning on percolation path and on the number of pinning centers are the dominant limitations of columnar pinning, leading to a limit of Bpin—4T.Evidence suggests that multiple-in-line-defects (MILD) are far better suited to increase Jc and Bpin,. The morphology of MILD pinning is reviewed. Ion energy loss per unit distance, Se, is found to be most promising in a regime almost diametrically opposite to that sought to maximize Upin. We expect Jc—10^6 A/cm^2 and Bpin＞,40 T from MILD pinning, despite sharply decreased Upin. Experimental confirmation is proposed.     

弱受端直流换相失败预防控制改进策略

高压直流(high voltage direct current, HVDC)输电系统作为中国能源远距离传输的重要载体,其稳定运行对电网具有重要意义,一旦发生换相失败,将对电网暂态稳定产生恶劣影响。为解决现有换相失败预防控制(commutation failure prevention, CFPREV)在某些故障情况下启动不及时的问题,通过引入换相电流时间面积判据,提出了一种启动更加迅速的换相失败预防控制改进策略,以中国某省实际电网为研究对象,在电力系统全数字实时仿真系统(advanced digital power system simulator, ADPSS)中建立其混合仿真模型。仿真结果表明,所提改进措施使得电网内高压直流输电系统具有更强的换相失败抑制能力及故障恢复能力。     

Superconducting Properties and Microstructure in MgB2 Bulks, Wires and Tapes

We prepared a series of MgB2 bulk samples under different temperatures, holding time and increasing rates in temperature by the solid state reaction. The thermodynamic behavior and phase formation in the Mg-B system were studied by using DTA, XRD and SEM. The results indicate that the formation of the MgB2 phase is very fast and the high increasing rate in temperature is necessary to obtain high quality MgB2. In addition, the effects of the Zr-doping in Mg1-xZrxB2 bulk samples fabricated by the solid state reaction at ambient pressure on phase compositions, microstructure and flux pinning behavior were investigated by using XRD, SQUID magnetometer, SEM and TEM. Critical current density Jc can be significantly enhanced by the Zr-doping and the best data are achieved in Mg0.9Zr0.1B2. For this sample, Jc values are remarkably improved to 1. 83 × 106 A/cm2 in self-field and 5. 51 × 105 A/cm2in 1T at 20K. Also, high quality MgB2/Ta/Cu wires and tapes with and without Ti-doping, MgB2/Fe wires and 18 filamen     

极光带电导率的日夜变化对高纬电离层电场的影响

在同时考虑极盖区电导率日大夜小和极光区电导率升高日小夜大两种效应的情况下,本文求出了高纬电场的分析解,并用其讨论了几个具体模式和对结果进行了分析。模式计算表明,极光带电导率升高的日夜变化对对流圈形态,电场分布和场向电流分布均有一定的影响,模式计算与观测比较有较好的一致性,这表明本文模式具有较好的应用意义。     

湖南高校高水平田径运动队建设现状及对策

运用文献资料、调查访问等方法,对湖南省普通高校高水平田径运动队建设的现状进行了剖析,并提出了相应的发展对策,为我省高校高水平田径运动队的建设提供参考.     

强流电子枪近阴极发射面区的分析与计算

近阴极发射面区的分析与计算是强流电子枪计算过程的一个关键环节．文中提出了该区在温度限制下交叉电磁场空间电荷流的理论分析，与Ｋｉｎｏ短枪流理论相结合，可以对交叉电磁场空间电荷流进行完整的计算．在此基础上研制的Ｃ形带状强流电子枪计算软件包已用于实际电子枪的计算，计算结果与实测一致     

海岸带林渔复合经营灯诱昆虫增饲螃蟹技术

用黑光灯将农、林、牧、蔬果及水域等昆虫引诱集中至精养蟹池中供螃蟹取食。能诱集昆虫近 30 0种 ,年诱虫重量达 90 .3～ 1 1 4.1kg/灯 ,每只螃蟹能取食昆虫 1 9.62± 2 8.1 5头 /晚 ,增加产量 1 1 8.35kg/hm2 ,增加产值 9468.0 0～ 1 42 0 2 .0 0元 /hm2 ,增产率达 2 2 .2 8%。同时减轻大田作物被害程度和减少化学农药的使用 ,优化生态环境