两族选代的不动点和Julia集

This paper proves that, for complex polynomials, all extraneous fixed pointsfor any iteration of Halley iterative family and another relevant iterative family arerepelling. Thus no false convergent phenomenon arises on these iterations.     

耦合Navier-Stokes/Darcy模型多重网格方法的有限元实现 [英文]

本文研究了耦合Navier-Stokes/Darcy模型问题。第一,构造了一种从粗网格到细网格的有限元空间插值方法,不但简化了数值积分的单元匹配,也保证了数值积分的精度。 第二,利用基于有限元空间的多重网格方法,获得了与直接法求解耦合问题误差相同的收敛 阶,推广了两重网格方法的结果。     

Theoretical study on the kesterite solar cells based on Cu_2ZnSn(S,Se)_4 and related photovoltaic semiconductors

The kesterite thin film solar cells based on the quaternary Cu_2ZnSnS_4 and Cu_2ZnSnSe_4 and their alloys Cu_2ZnSn(S,Se)_4 have been considered as environment-friendly and non-toxic alternatives to the currently commercialized Cd Te and Cu(In,Ga)Se_2 thin film solar cells.From the theoretical point of view,we will review how the group Ⅰ_2-Ⅱ-Ⅳ-Ⅵ_4 quaternary compound semiconductors are derived from the binary CdTe and the ternary CuInSe_2 or CuGaSe_2 through the cation mutation,and how the crystal structure and electronic band structure evolve as the component elements change.The increased structural and chemical freedom in these quaternary semiconductors opens up new possibility for the tailoring of material properties and design of new light-absorber semiconductors.However,the increased freedom also makes the development of high-efficiency solar cells more challenging because much more intrinsic point defects,secondary phases,surfaces,and grain-boundaries can exist in the thin films and influence the photovoltaic performance in a way different from that in the conventional Cd Te and Cu(In,Ga)Se_2 solar cells.The experimental characterization of the properties of defects,secondary phase,and grain-boundaries is currently not very efficient and direct,especially for these quaternary compounds.First-principles calculations have been successfully used in the past decade for studying these properties.Here we will review the theoretical progress in the study of the mixed-cation and mixed-anion alloys of the group Ⅰ_2-Ⅱ-Ⅳ-Ⅵ_4 semiconductors,defects,alkaline dopants,and grain boundaries,which provided very important information for the optimization of the kesterite solar cell performance.     

关于反函数定理

在函数解析的假设下，Ｓｍａｌｅ利用其α判据对反函数存在邻域的半径给出了一个估计．本文不仅将此估计精确化，而且把假设条件放宽为二次连续可微．     

Euler级数的收敛性与组合学技巧

通过优序列方法，建立了Ｅｕｌｅｒ级数，即反函数的幂级数的收敛性，而且，我们发现Ｅｕｌｅｒ级数的系数和具有ｎ个元素的Ｓｃｈｒｏｄｅｒ系的个数之间的联系，以及Ｅｕｌｅｒ级数收敛半径的确切下界可通过相应的指母函数的收敛半径得到 。     

Numerical simulation for all-optical Thomson scattering X-ray source

Energy spectra, angular distributions, and temporal profiles of the photons produced by an all-optical Thomson scat- tering X-ray source are explored through numerical simulations based on the parameters of the SILEX-I laser system （800 nm, 30 fs, 300 TW） and the previous wakefield acceleration experimental results. The simulation results show that X-ray pulses with a duration of 30 fs and an emission angle of 50 mrad can be produced from such a source. Using the optimized electron parameters, X-ray pulses with better directivity and narrower energy spectra can be obtained. Besides the electron parameters, the laser parameters such as the wavelength, pulse duration, and spot size also affect the X-ray yield, the angular distribution, and the maximum photon energy, except the X-ray pulse duration which is slightly changed for the case of ultrafast laser-electron interaction.     

利用轫致辐射谱回推超热电子温度

超短超强激光打靶产生的超热电子与固体靶相互作用时会产生轫致辐射X射线。利用蒙特卡罗方法,对电子在固体靶中传输产生的轫致辐射X射线进行了模拟。1 MeV电子束与固体靶作用产生的轫致辐射谱模拟结果表明,轫致辐射谱高能段斜率受靶厚度及靶材料的影响不明显。麦克斯韦分布的电子束及单能电子束与30 m铜靶作用的模拟结果显示,两种电子源产生的轫致辐射谱在电子束能量或温度较高时基本一致。给出了一种利用轫致辐射谱斜率反推超热电子温度的定标方法。模拟了不同温度下超热电子产生的轫致辐射光子的能量角分布及光子数角分布,结果显示辐射光子能量通量和光子数随着电子温度的提高越来越向前倾,并给出了另外一种由轫致辐射能量角分布反推超热电子温度的定标关系。     

针对高压物质密度诊断的激光X射线照相优化设计

激光驱动冲击波能提供高压的物质状态, 是状态方程研究的重要工具. 超短超强激光与固体靶相互作用产生的X射线源, 具有短脉冲、微焦点、高产额、能量可调的特点, 是高压物质密度测量的首选背光源. 本文基于蒙特卡罗程序Geant4建立了X射线照相模型, 客体密度分布由流体力学程序Multi-1D模拟激光冲击加载高压物质获得. 在一维长方体形密度客体情况下, 定义了均方根、峰值偏差与上升沿斜率比三种指标, 对照相图像求解的密度结果进行评价, 开展了照相结果信噪比、分辨率与对比度等参数优化. 并开展了一维圆柱形密度客体的照相模拟, 建立了基于Radon逆变换法的Abel反演算法. 反演结果与模拟设计密度分布符合良好, 要求X射线源半径在5 μm以内; 反演结果与模拟设计密度分布较为一致, 要求X射线源半径在15 μm以内.     

慢性电刺激海马结构诱发大鼠脑磁共振成像异常信号分析

为探讨海马结构(hippocampal formation)功能失衡与癫痫源性脑损伤的关系,本工作采用 慢性强直电刺激大鼠海马(hippocampus, HPC) CA1顶树突区（apical dendrite region, A DR）或齿状回（dentate gyrus, DG）诱发大鼠癫痫模型,一天一次,连续刺激6～8天后, 观察人工致痫灶以外的横向弛豫时间加权的核磁共振(T₂ weighted magnetic reson ance im age, T₂-WI) 绝对信号值变化（片厚1mm）,以及深部电图和原发性湿狗颤抖（pri mary wet dog shakes, WEDS）,并对被检测动物T₂-WI信号异常的相应脑区进行组织学鉴定. 结果表明：（1）电 刺激大 鼠ADR或DG的作用基本相似,引起深部电图的癫痫样电活动和侧脑室区域T₂值增强.（2）含有电极尖端痕迹的核磁共振（magnetic resonance image,MRI）脑切片出现对称性腹部侧脑室区域T₂值增强,连续向后1mm取MRI脑切片进行观察发现,对侧腹部侧脑室区域信号异常. （3）组织学切片观察到：MRI检测的侧脑室区域T₂-WI信号增强与组织切片的侧脑室扩大相吻合,可见扩大的侧脑室中脉络丛上皮细胞病理性增生现象. 提示：在大鼠癫痫点燃现象出现之前,过度激活DG或ADR均可引起相似的早期癫痫源性脑损伤.     

非理想背光照相对靶壳阿贝尔密度反演的影响

建立了背光照相的模拟手段,研究了记录屏像素尺寸、背光强度分布、背光光谱非单色、针孔弥散及针孔形状对惯性约束聚变中常用塑料球壳的阿贝尔密度反演的影响。结果表明:较大的记录屏像素尺寸会掩盖密度分布的细节;高斯型的背光空间分布会使密度分布低于真实值,可能导致非物理的负密度分布;采用Mo的L带谱线作为背光源也会导致反演密度偏离真实值;当壳层厚度小于针孔尺寸时,针孔弥散效应会显著降低峰值密度,利用维纳滤波法处理背光图像后密度反演的结果得到明显改善;相同针孔面积条件下,椭圆形针孔给出的峰值密度要低于圆形针孔的结果。