共面双对称条件下电子碰撞Ar原子单电离的一阶扭曲波Born近似

在共面双对称几何条件下,利用一阶扭曲波Born近似计算了中低能电子碰撞Ar原子(3p壳层电子)单电离的三重微分截面,并与最近的实验数据做了比较.结果表明,对于Ar原子,当入射电子能量比电离阈高40 eV以上,随着入射能量的增加,binary和recoil碰撞机理逐渐占据支配地位;在近阈能量范围,上述碰撞机理不再处于支配地位,扭曲效应明显.要完备地描述中低能入射条件下Ar原子的电子碰撞电离过程,理论模型必须同时考虑多种散射机理.     

Micro‐analysis on Chinese over‐glaze red decoration of Linshui Kiln from Jin dynasty (1115–1234 ad)

Red and green over‐glaze decoration on Chinese porcelains from the Song‐Jin periods is critical to the development for Chinese ceramics. To characterize the identity, crystal size, and band gap width of the red colorant, red and green porcelain shards from the Linshui kiln produced in the Jin dynasty (1115–1234 ad ) are investigated using Raman spectroscopy, X‐ray diffractometry, and diffuse reflectance measurements. The colorant is shown to comprise hematite crystallites with the average diameter around 30 nm, and its crystal lattice is distorted as the result of the low firing of the decoration. The use of crystal size estimations coupled with band gap width calculations are believed to be employed for the first time on the study of Chinese archeological artifacts. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparisons in the mean residual life order of coherent systems with identically distributed components

The comparisons of the performance of coherent systems (under different stochastic criteria) is an important task in the reliability theory. Several results have been obtained in the literature for the stochastic, hazard rate and likelihood ratio orders. In this paper, we obtain comparison results for the mean residual life order of coherent systems with identically distributed (ID) component lifetimes. These results can be applied not only to the usual case of systems with independent and identically distributed components but also to the case of systems with exchangeable components and to the more general case of just ID components. The results obtained are based on the representation of the system distribution as a distorted distribution of the common components' distribution. Some specific comparison results are given to illustrate the theoretical results. The comparison results for distorted distributions given here can also be applied to other statistical concepts such as order statistics, generalized order statistics or record values. Copyright © 2015 John Wiley & Sons, Ltd.     

A calcium(II) coordination polymer showing two different bridging 2-carbamoyl-4-nitrobenzoate coordination modes

Aqueous reaction of CaCO₃ with 2-carbamoyl-4-nitrobenzoic acid (2-ca-4nbaH) results in the formation of a 1-D coordination polymer [Ca(H₂O)₂(2-ca-4nba)₂] (1), which crystallizes in the centrosymmetric triclinic space group P 1. The structure consists of a central Ca(II), two coordinated waters, a symmetrical bridging (µ₂-η ¹ : η ¹) 2-ca-4nba, and a tridentate bridging (µ₂-η ² : η ¹) 2-ca-4nba. The calcium in 1 is coordinated by two water molecules and five oxygens of four symmetry-related 2-ca-4nba, resulting in a distorted pentagonal bipyramidal {CaO₇} polyhedron. Pairs of {Ca(H₂O)₂} units are linked into a 1-D coordination polymer extending along the a-axis with the aid of pairs of bridging 2-ca-4nba ligands. In the infinite chain, alternating pairs of Ca(II) ions exhibit Ca ··· Ca separations of 4.124 and 4.855 Å.