Analysis of Ar line spectra from indirectly-driven implosion experiments on SGII facility

This paper reports on the indirectly-driven implosion experiments on SGII laser facility in which Ar emission spectrum from Ar-doped D-filled plastic capsule is recorded with the crystal spectrometer. Spectral features of Ar Heβ line and its associated satellites are analysed to extract the electron temperature and density of the implosion core. Non local thermal equilibrium (NLTE) collisional-radiative atomic kinetics and Strark broadening line shape are included in the present calculation. By comparing the calculated spectrum with the measured one, the core electron temperature and density are inferred to be 700 eV and 2.5×10²³ cm^-3 respectively. With these inferred values of electron temperature and density, neutron yield can be estimated to agree with the measured value in magnitude despite of the very simple model used for the estimation.     

慧眼识“圆”,拓宽解题路径

<正>《墨子·经上》记载:“圜,一中同长也”,其大意为圆这种图形有一个中心,从这个中心到圆上各点长度相等.这是中国古人对于圆这一几何概念的定义,用现代数学语言描述即为“圆是到定点(圆心)的距离等于定长(半径)的所有点的轨迹”.圆作为初中平面几何的重要内容,在历年中考数学试卷中均占有一席之地.从各地命题的方式来看,除了直接考察圆的基础知识以外,一类隐圆问题也备受命题者的青睐,     

钠在空位石墨烯上吸附性能的研究

采用基于密度泛函理论的第一性原理方法,研究了本征石墨烯和空位石墨烯吸附钠原子的电荷密度、吸附能、态密度和储存量.结果表明,在两种石墨烯中,钠原子的最佳吸附位置都为H位.空位石墨烯对钠原子的吸附能是-2. 46 eV,约为本征石墨烯对钠原子吸附能的3. 4倍;钠原子与空位石墨烯中的碳原子发生轨道杂化,而与本征石墨烯没发生轨道杂化现象.存在一个空位的石墨烯能够吸附5个钠原子,与本征石墨烯相比显著提高.因此,空位石墨烯有望成为一种潜在的储钠材料.     

一种简单的局部离散速度统一气体动理论格式

统一气体动理论格式UGKS(Unified Gas-Kinetic Scheme)是一种适用于从连续流到自由分子流的全流域计算格式。在该格式中一般使用统一的离散速度空间。而在高速流动中,不同节点的分布函数往往差异很大。为了保证计算的精度,离散速度空间必须满足所有节点的需要,占用了大量的内存。采用局部的均匀离散速度空间,离散速度的范围随节点状态的变化而变化,从而降低了内存的需要,并通过引入背景网格避免了不同节点离散速度的插值。最后,通过两个一维算例对该方法进行了测试。测试结果显示,采用局部离散速度空间能够得到可靠的结果,并且在模拟高速流动时计算效率明显提高。     

Numerical investigation on broadband mid-infrared supercontinuum generation in chalcogenide suspended-core fibers

As_2S_3 and As_2Se_3 chalcogenide 3-bridges suspended-core fibers(SCFs) are designed with shifted zero-dispersion wavelengths(ZDWs) at around 1.5 μm, 2 μm, and 2.8 μm, respectively. A generalized nonlinear Schr ¨odinger equation is used to numerically compare supercontinuum(SC) generation in these SCFs pumped at an anomalous dispersion region nearby their ZDWs. Evolutions of the long-wavelength edge(LWE), the power proportion in the long-wavelength region(PPL), and spectral flatness(SF) are calculated and analyzed. Meanwhile, the optimal pump parameters and fiber length are given with LWE, PPL, and SF taken into account. For As_2S_3 SCFs, SC from a 14 mm-long fiber with a ZDW of 2825 nm pumped at 2870 nm can achieve the longest LWE of ～ 13 μm and PPL up to ～72%. For As_2Se_3 SCFs, the LWE of 15.5 μm and the highest PPL of ～ 87% can be achieved in a 10 mm-long fiber with ZDW of 1982 nm pumped at 2000 nm. Although the As_2Se_3 SCFs can achieve much longer LWE than the As_2S_3 SCFs, the core diameter of As_2Se_3 SCFs will be much smaller to obtain a similar ZDW, leading to lower damage threshold and output power. Finally, the optimal parameters for generating SC spanning over different mid-IR windows are given.     

基于局部相互作用理论的侵彻弹头部形状优化及仿真

以局部相互作用理论为基础,引入与弹体头部形状相关的开坑计算方法和归一化弹体头部形状方程,给出了任意头部形状弹体侵彻混凝土深度的计算模型。利用最大侵深法,得到了无量纲头部形状控制参数表达式及经典变分头部形状优化设计方法。理论计算及弹靶分离仿真模拟计算结果与实验结果吻合较好。研究结果表明:弹体头部相对半径较小时,球头锥形和球头卵形弹体优化后得到的头部形状分别为尖头锥形和尖头卵形;优化截头弹体的侵彻深度大于优化尖头弹体,而优化截锥形弹体的侵彻深度最大;弹体头部形状对弹体侵彻过载的影响显著,优化弹体头部形状可以有效地提高侵彻深度。     

影响TiMnx非计量比合金储氢容量的结构因素

以TiMn_x (x = 1.4, 1.5, 1.6, 1.7)非计量比合金为对象,系统研究了储氢容量与其内在结构之间的相关性。结果表明,所有合金的主相均为C14型Laves相,但其储氢容量却存在显著差异。其中TiMn_1.4合金的储氢量约为0.65% (w,质量分数),吸/放氢平台较倾斜,且存在明显的滞后;而TiMn_1.5合金的可逆储氢量达到1.2% (w),平台较为平坦;但继续增加x,其储氢量反而降低,如x = 1.6合金的储氢量仅为0.30% (w),而x = 1.7合金则几乎不吸氢。进一步结构解析表明,上述储氢容量的迥异主要归因于部分Ti原子占据Mn(2a)位置,且其占位率随x的增加而降低,随之C14相中贮氢四面体间隙体积减小;而引起贮氢四面体间隙体积发生变化的主要因素是Ti―Ti键和Mn(2a)―Mn(2a)键的键长,其中Mn(2a)―Mn(2a)键长的增加对合金储氢容量的提升起关键作用。     

卵形弹体侵彻预开孔靶理论分析

以破爆型串联战斗部后级随进弹对预开孔靶侵彻过程为研究对象,基于锥形预开孔和库仑摩擦模型,发展完善了包括扩孔/开坑和稳定侵彻的卵形弹体侵彻预开孔靶理论模型。分别对该模型在侵彻脆性和弹塑性靶体的有效性进行了实验验证。利用该模型分析了弹头曲径比、预开孔直径、预开孔形状等对侵彻结果的影响。研究结果表明:发展完善的模型计算结果与实验数据吻合较好。柱形开孔情况下,侵彻速度、弹头曲径比及相对孔径同侵彻深度呈正比;在侵彻容积相同的条件下,弹体侵彻预开锥孔的侵深结果与锥角及相对入孔孔径变化关系较大。     

一维周期性梁结构等效性能计算方法讨论

具有轴向周期微结构的复合梁结构,通常在宏观上简化为一维欧拉-伯努利梁。由于缺乏基于严格数学理论、同时考虑降维及均匀化的等效性能计算方法,已有研究或采用基于平截面假定的弯曲能量近似方法,或采用基于三维周期性介质等效性质的方法。本文首先介绍了基于一维周期性梁的渐近均匀化理论求解新方法,并在此基础上与上述两种方法进行比较。结果表明,基于平截面假定的近似方法忽视了这类梁结构内的三维应力状态,过高地估计了梁的等效性质。     

Structural optimization and segregation behavior of quaternary alloy nanoparticles based on simulated annealing algorithm

Alloy nanoparticles exhibit higher catalytic activity than monometallic nanoparticles, and their stable structures are of importance to their applications. We employ the simulated annealing algorithm to systematically explore the stable structure and segregation behavior of tetrahexahedral Pt–Pd–Cu–Au quaternary alloy nanoparticles. Three alloy nanoparticles consisting of 443 atoms, 1417 atoms, and 3285 atoms are considered and compared. The preferred positions of atoms in the nanoparticles are analyzed. The simulation results reveal that Cu and Au atoms tend to occupy the surface, Pt atoms preferentially occupy the middle layers, and Pd atoms tend to segregate to the inner layers. Furthermore, Au atoms present stronger surface segregation than Cu ones. This study provides a fundamental understanding on the structural features and segregation phenomena of multi-metallic nanoparticles.