Beam dynamics studies on BEPC-Ⅱstorage rings at the commissioning stage

During the 1st and 2nd stages of the commissioning of the upgrade project of the Beijing Electron Positron Collider(BEPC Ⅱ),which started on Nov.12,2006 and Oct.24,2007,respectively,we got the luminosity one tenth of its design value,provided beams to synchrotron radiation users for about 4 months,and studied beam dynamics as well.In this paper,some beam dynamics studies on the storage rings and their preliminary results are given.     

Research Progress of Lithium Plating on Graphite Anode in Lithium‐Ion Batteries

Lithium plating on graphite anode is triggered by harsh conditions of fast charge and low temperature, which significantly accelerates SOH (state of health) degradation and may cause safety issues of lithium ion batteries (LIBs). This paper has reviewed recent research progress of lithium plating on graphite anode. Firstly, we summarize the forming mechanisms of Li plating with corresponding influence factors, the detecting methods and hazard of Li plating. Then, approaches to suppress Li plating are discussed, including anode surface modification, electrolyte composition optimization and development of optimal charge strategies. Finally, we conclude and propose the remaining challenges and prospects in terms of mechanism research, detecting approaches, and suppressing methods of Li plating. This review highlights the development of Li plating research and plays a guiding rule of further study on Li plating in LIBs.     

Theoretical analysis of magnetic sensor output voltage

The output voltage is an important parameter to determine the stress state in magnetic stress measurement, the relationship between the output voltage and the difference in the principal stresses was investigated by a comprehensive application of magnetic circuit theory, magnetization theory, stress analysis as well as the law of electromagnetic induction, and a corresponding quantitative equation was derived. It is drawn that the output voltage is proportional to the difference in the principal stresses, and related to the angle between the principal stress and the direction of the sensor. This investigation provides a theoretical basis for the principle stresses measurement by output voltage.     

Examples of entropy generating sequence

We introduce the notion of entropy generating sequence for infinite words and define its dimension when it exists. We construct an entropy generating sequence for each symbolic example constructed by Cassaigne such that the dimension of the sequence is the same as its topological entropy dimension. Hence the complexity can be measured via the dimension of an entropy generating sequence. Moreover, we construct a weakly mixing example with subexponential growth rate.     

Pseudo-relaxor behaviour induced by Maxwell–Wagner relaxation

We performed a further investigation on the Maxwell–Wagner (MW) relaxation-induced relaxor-like dielectric response characterized by a broad peak in the real part of the dielectric permittivity as a function of temperature. Based on the double-layer MW model formulated by Catalan et al. (2000) [10], an empirical formula was derived to describe the temperature dependence of the peak intensity. It was also found that the temperature dependence of the peak position can be characterized by an Arrhenius-like relation. The differences between the true relaxor and MW-related relaxor behaviours are also discussed.     

Stable conformations of 12-crown-O3N and its Li+ complex in aqueous solution

Stable conformations of 12-crown-O3N and its Li complexes in aqueous solution were investigated. To calculate the free energy differences of conformers of 12-crown-O3N and its Li+ complex, our procedure was to make use of two programs, CONFLEX and BOSS. The former generates conformers, and the latter calculates the differences in free energy of solvation between two conformers in aqueous solution. It was confirmed that the present procedure is applicable in solving the question of what is the most stable conformation of 12-crown-O3N in aqueous solution. Results of the calculations suggest that the order of stability for conformers in a vacuum is different from that in aqueous solution. It was also confirmed that the coordination geometry of solvent waters to Li+ changes depending on the distance between the cation and the crown ring.     

掺杂纳米半导体超微粒ZnS:Mn2+光学特性研究

九十年代对纳米尺寸(nanoscale)材料的光物理性质的深入研究,导致了介于微观与宏观物理间的新的学科一介观物理(mesoscopic physics)的产生.其科学义在于建立和发展介于原子分子和固体之间所谓介观系统(mesoscopic system)的量子理论,揭示介观物质特性及其相互作用本质,并利用介观特性探索新型结构和功能材料.以往对纳米半导体超微粒材料的研究主要集中于与本征特性相关的量子尺寸效应,或缺陷对超微粒本征特性的影响[1,2].超微粒中过渡金属离子中心发光性质研究首次报道于1993年[3,4]并指出这可能成为崭新的一类发光材料.