Electronic Structure and Magnetism in Sm（Co,Cu）7

The electronic density of states, spin-splittings and atomic magnetic moments of SmCo7-xCux are studied by means of the spin-polarized multi-scattering Xα method. The results show that a few of the electrons can transfer to the Sm 5d^0 orbital due to orbital hybridization between Sm and Co. The exchange interactions between 3d and 5d electrons lead to the magnetic coupling between Sm and Co, and therefore result in the long-range ferromagnetic order in SmCo7-xCux. The Curie temperature of SmCo7-xCux is generally lower than that of the corresponding pure Co, which may be explained by the weaker average strength of coupling between Co lattices due to some negative exchange couplings mainly from the 2e site. The calculated results for the Sm5Co3oCu4 cluster may lead to a better understanding of why SmCo7-xCux is stable phase. Since the negative coupling of the 2e sites becomes small and the d bond at EF becomes stronger in contrast to SmCo7, which results in decrease of the free energy of the system, the stable ferromagnetic order forms in SmCo7-xCux.     

An Advanced Dynamic Model for Semiconductor Optical Amplifiers and Laser Diodes

We propose a unified time-domain dynamic model for both semiconductor optical amplifiers and laser diodes by employing a set of multi-longitudinal-mode coupled wave rate equations. A novel split-step method has been developed for the numerical solution of the equation set. To demonstrate the capabilities of the model, some calculation results for conventional and distribute feedback-type gain-clamped semiconductor optical amplifiers are presented.     

Correlation between Light Emissions from Amorphous-Si：H/SiO2 and nc-Si/SiO2 Multilayers

We investigate the properties of light emission from amorphous-Si：H/SiO2 and nc-Si/SiO2 multilayers （MLs）. The size dependence of light emission is well exhibited when the a-Si：H sublayer thickness is thinner than 4 nm and the interface states are well passlvated by hydrogen. For the nc-Si/Si02 MLs, the oxygen modified interface states and nanocrystalline silicon play a predominant role in the properties of light emission. It is found that the light emission from nc-Si/SiO2 is in agreement with the model of interface state combining with quantum confinement when the size of nc-Si is smaller than 4 nm. The role of hydrogen and oxygen is discussed in detail.     

利用胶体小球掩蔽刻蚀技术制备的半导体纳米阵列的场电子发射特性

利用胶体小球掩蔽刻蚀技术,制备了单晶硅纳米阵列,利用原子力显微镜观察了硅阵列的表面形貌,实验结果表明,硅柱阵列具有高密度和较好的均匀性。同时研究了单晶硅纳米阵列的场电子发射特性。为了提高样品的场发射性能,在所制备的单晶硅有序纳米阵列上生长了一层非晶碳薄膜。与单晶纳米硅柱阵列相比,覆盖有非晶碳膜的样品的场电子发射特性有了明显的改善,表现在场发射的开启电场下降,同时场发射增强因子得到增加。结果表明非晶碳膜确实能够降低电子发射的表面有效势垒,从而增强了场电子发射特性。     

原位自生TiC对低合金马氏体钢磨料磨损性能的影响

以新型含TiC马氏体钢Ti60和商用不含碳化物马氏体钢JFE400为研究对象,通过三体磨料磨损试验机研究在纯煤粉和纯煤粉掺杂40%(质量分数)石英砂为磨料下,TiC硬质相对低合金马氏体钢磨料磨损性能的影响及其作用机理. 结果表明:在纯煤粉环境下,Ti60钢的磨损体积大于JFE400钢;但在纯煤粉掺杂40%(质量分数)石英砂环境下,Ti60钢的磨损体积却小于JFE400钢. 根据磨痕表面的形貌,上述结果是由以下几方面综合作用造成的. 首先,两种环境下材料的磨损机制均主要是犁削磨损;其次,煤粉颗粒的层状结构及低硬度的特性,使得TiC硬质相对其犁削行为起不到阻碍作用,而块状结构且具有高硬度的石英砂颗粒的犁削行为则受到TiC硬质相的阻碍. 所以在纯煤环境下,基体硬度较大的JFE400钢,相对于基体硬度较小的Ti60钢,呈现出较优的抗磨料磨损的性能. 而在纯煤粉掺杂40%(质量分数)石英砂环境下,Ti60钢的抗磨粒磨损性能却优于JFE400钢.      

1.7MeV电子辐照对CdTe太阳电池电流传输特性影响的图谱分析（英文）

研究了1.7 MeV的电子辐照对具有Anti-radiation glass/ITO/ZnO/CdS/CdTe/ZnTe/ZnTe:Cu/Ni结构的碲化镉多晶薄膜太阳电池器件性能的影响。抗辐照玻璃的使用,有效防止了普通玻璃受辐照后性能变化对测试结果的影响。利用光、暗I-V,C-V,QE,AS等测试手段,分析了包括开路电压、短路电流、转换效率在内的电池性能。通过对比研究暗电流密度、分析了辐照对电池电流传输特性的影响。辐照后短路电流下降很大,电池效率明显降低。反向饱和电流密度有所增加,表明太阳电池的pn结特性受到损伤,而二极管理想因子几乎不变,说明太阳电池电流的输运机制未发生了变化。量子效率曲线证明是由于太阳电池结区损伤影响了光生载流子的收集。辐照使载流子浓度下降为原来的40.6%。导纳谱研究最终发生辐照会引入Cd~(2+)缺陷能级,其位置为E_1—E_v=(0.58±0.02)eV,俘获截面为1.78×10~(-16)cm~2,表明辐照会影响光生载流子的产生,增加了载流子复合的概率,使得反向暗电流增大,最终导致电池的短路电流衰减。     

利用Riemann-Hilbert方法产生Ernst方程严格解的新途径

为了得到引力场中Ernst方程的更多新严格解,人们根据无穷维ceroch群,即数学上的Kac-Moody 群的表示,在构造生成新解的对称变换方面取得了很大的进展.其中最引人注目的结果之一是Hoenselaers-Kinnersley-Xanthopoulos(HKX)变换的发     

超主手征场模型中的无穷保形对称性和Riemann-Hilbert变换

我们在超主手征场模型中找到了一种新的对变换——C变换,发现在这种变换下体系具有一个与没有中心项的Virasoro代数相关的无穷维李代数,利用Riemann-Hilbert变换,我们探讨了C变换的物理根源.     

静轴对称Einstein-Maxwell引力场的新对称性

我们把以前在真空Ernst场中得到的无穷小对称变换推广到带电磁场的Ernst场中,得到了一个更大的无限维对称群,这个群与不带中心项的Virasoro群同构.我们从中找到一个子群,即扩大Cosgrove群.最后,我们指出用这个新发现的无穷小变换,可以从已知带电磁场的Ernst场方程解,获得一个新解.     

烧结Nd-Fe-B磁体的微观结构和冲击韧性研究

对烧结Nd₁₅Fe_72-xCo_yNb_xB₈(y=0, 5;x=0, 05, 10, 15, 20, 25)永磁体的微观结构和冲击韧性及二者间的关系进行了研究.结果表明，添加Nb能够改善Nd-Fe-B磁体的微观结构，提高磁体的冲击韧性.当无Co磁体中Nb的原子百分含量为15%时，其冲击韧性达到最大；对于添加了Co的磁体，其冲击韧性的