MAl_(12)(M=Ni、Mn)及其阴离子团簇的几何结构和磁性的计算研究

采用密度泛函理论(density functional theory,DFT)中的广义梯度近似(generalized gradient approximation,GGA)分别对Al_(13)和MAl_(12)(M=Ni、Mn)四种初始结构的中性和一价阴离子团簇进行计算研究.发现中性和阴离子团簇的基态几何结构均保持I_h对称性,并且基态阴离子团簇还具有较高的运动学稳定性.电磁性质计算显示:基态的中性和阴离子NiAl_(12)团簇分别带有2_(μB)、3_(μB)的磁矩,Ni原子的磁性几乎完全淬灭;而MnAl_(12)团簇分别带有7_(μB)、6_(μB)的磁矩,Mn原子的磁矩主要由3d轨道提供.基态团簇的表面原子出现了自旋分裂,与中心原子呈现出铁磁性作用.对垂直电离能和垂直亲和能的分析表明:中心原子被替代之后,团簇的得电子能力和失电子能力都有所降低.     

自洽平均值近似方法求解三维非线性谐振子的能级和波函数

采用自洽平均值近似法求解三维非线性谐振子的能量本征值,并与其精确解和微扰论结果相比较,结果表明,自洽平均值近似法求得的能量本征值不仅引入的误差较小,且计算过程也得到了简化.     

Dressed Four-Wave Mixing Spectroscopy Modified by Polarization Interference and Atom-Wall Collision in Micrometric Thin Cells

Dressed four-wave mixing （DFWM） spectroscopy is investigated theoretically in some micrometric thin cells. It is found that DFWM spectra can be modified by polarization interference of atoms and transient effects induced by atom-wall collision. This modification can lead to width-narrowing of DFWM lines and facilitates to implement experiment of high resolution DFWM spectroscopy in a confined atomic system.     

Numerical Simulations of Calcium Ions Spiral Wave in Single Cardiac Myocyte

The calcium ions （Ca^2＋） spark is an elementary Ca^2＋ release event in cardiac myocytes. It is believed to buildup cell-wide Ca^2＋ signals, such as Ca^2＋ transient and Ca^2＋ wave, through a Ca^2＋-induced Ca^2＋ release （CICR） mechanism. Here the excitability of the Ca^2＋ wave in a single cardiac myoeyte is simulated by employing the fire-diffuse-fire model. By modulating the dynamic parameters of Ca^2＋ release and re-uptake channels, we find three Ca^2＋ signaling states in a single cardiac myoeyte： no wave, plane wave, and spiral wave. The period of a spiral wave is variable in the different regimes. This study indicates that the spiral wave or the excitability of the system can be controlled through micro-modulation in a living excitable medium.     

Permanent Magnetic Properties of Melt-Spun YCo5Cx Ribbons

Ribbons of nominal compositions YCo5 Cx （x = 0, 0.2, 0.4, 0.6） are prepared by melt spinning at surface velocities v = 5, 10, 15, 20, 25, 30 and 35 m/s. YCo5 ribbon is crystallized in a single YCo5 phase of hexagonal CaCu5 structure. A small quantity of YCoC2 phase appears in the ribbons with C addition besides the YCo5 phase. With the increase of x the lattice constant c increases and a along with the unit cell volume decreases. The largest values of iHc = 888 kA/m and （BH）max = 58.4 k Jim3 at present for the YCo5 ribbon system were obtained with x = 0.4 and v = 20 m/s. The improvement of the permanent magnetic properties is rooted in the refinement of the microstructure and the appearance of the YCoC2 phase which can act as domain wall pinning centers.     

Glassy metallic plastics

This paper reports a class of bulk metallic glass including Ce-, LaCe-, CaLi-, Yb-, and Sr-based metallic glasses, which are regarded as glassy metallic plastics because they combine some unique properties of both plastics and metallic alloys. These glassy metallic plastics have very low glass transition temperature (Tg~25oC to 150oC) and low Young’s modulus (~20 GPa to 35 GPa). Similar to glassy plastics, these metallic plastics show excellent plastic-like deformability on macro-, micro- and even nano-scale in their supercooled liquid range and can be processed, such as elongated, compressed, bent, and imprinted at low temperatures, in hot water for instance. Under ambient conditions, they display such metallic properties as high thermal and electric conductivities and excellent mechanical properties and other unique properties. The metallic plastics have potential applications and are also a model system for studying issues in glass physics.     

照度对测量三代微光像增强器MTF的影响分析

通过探讨像增强器MTF测试仪用光源的出射光照度对测量结果的影响,对透过测量狭缝的光强分布进行了分析.调节狭缝面的入射光照度,对不同照度作用下的调制传递函数进行了对比测量,经与微光像增强器的饱和输出亮度比较,得出:三代微光像增强器的MTF测试值随入射光照度分布呈抛物线分布,其最大值与微光像增强器的自动亮度控制特性有关.适当选择入射光照度,可确保被测像增强器既有足够的输出信噪比,而不进入饱和区域.     

宽谱段光学系统消二级光谱的设计

利用修正的部分色散(P)和阿贝数(V)公式,计算一些典型的普通光学玻璃在450nm～950nm波段的色散特性,应用二级光谱理论,采用普通光学材料,设计了一个复消色差系统,分析近红外波段光学系统的二级光谱特性及校正方法,给出设计实例。设计结果表明:在可见光近红外波段,采用重冕玻璃ZK4、ZK8和特种火石玻璃TF3组合实现了二级光谱色差的校正,即从理论的0.18mm减少到0.084mm,证明该系统有较好的消色差能力,并且具有较长的后截距,为安装像移补偿反射镜提供了方便。     

20Mgβ衰变谱学与15O(α,γ)19Ne反应(英文)

15O（α,γ）19Ne（p,γ）20Na反应链是高温CNO循环向快速质子俘获过程突破的一条关键路径,相关的反应率输入量可通过20Mg的β衰变可布居19Ne共振态并测量其衰变性质来获得。通过高效率高精度地测量20Mg β衰变中产生的质子与γ射线得到了20Mg衰变的详细信息,并构建了完整的衰变纲图,还进行了19Ne 4 033 keV共振态衰变性质的探索,获得了该态在20Mg β衰变中被布居的分支比上限。通过比20Mg和20O镜像能级跃迁的结果确认了同位旋非对称性,为检验相关理论模型提供了精确的实验数据。对于突破路径中有重要影响的19Ne 4 033 keV共振态的性质,有待更高统计的实验进一步研究。The breakout from the hot CNO cycle to the rapid proton capture process can occur via the 15O(α,γ)19Ne(p,γ)20Na reaction sequence, and the β decay of 20Mg can be used as an alternative method to characterize some specific resonances, which will provide detailed nuclear structure input for reaction rate calculations. The reliable information on the decay properties and structure of 20Mg was obtained by measuring the emitted particles and γ-rays in the β decay with high efficiency and high resolution. Attempt was also made to search for the decay channels associated with the 4 033 keV resonance in 19Ne. To test fundamental symmetries, the transitions in the mirror decays of 20Mg and 20O were compared. The precise experimental data presented here would be important to constrain the theoretical calculations. It is desirable to clarify the astrophysically relevant problem by further experiments with improved statistics on the basis of the present work.     

弱激波冲击无膜重气柱和气帘界面的实验研究

研制了一个改进的激波管设备,对马赫数为1.2的弱激波冲击作用下空气中SF6气柱和气帘界面的演变过程进行了初步的实验研究。通过设计激波管实验段、烟雾发生器、气体箱、进气吸气系统和激波管尾段,控制混合气体中SF6的峰值浓度和初始气流速度,建立了稳定、可重复的无膜气柱和气帘初始界面形成技术。利用高速摄影技术,在水平面内观测了气柱和气帘的初始界面图像,沿垂直方向观测了界面RM(Richtmyer-Meshkov)不稳定性的演变过程。气柱演变图像显示了典型的对涡结构,气帘演变图像显示了早期的多蘑菇形结构和后期的相邻波长干扰效应。图像后处理表明,气柱的高度和宽度、气帘的宽度均随时间单调增加,且宽度比高度增加快得多。从二维涡量动力学方程出发,对图像中涡的演变过程进行了初步解释。