Assembly maps,K-theory, and hyperbolic groups

Following Connes and Moscovici, we show that the Baum-Connes assembly map forK _*(C*v) is rationally injective when is word-hyperbolic, implying the Equivariant Novikov conjecture for such groups. Using this result in topologicalK-theory and Borel-Karoubi regulators, we also show that the corresponding generalized assembly map in algebraicK-theory is rationally injective.     

ICF靶丸装配误差检测

针对激光惯性约束聚变装置中靶丸装配误差检测困难、要求精度高的特点,研制了一套用于微靶装配参数检测的测量系统。提出了一种基于激光与CCD的复合式测量方法,建立了二者数据融合的数学模型,通过标定空间位置关系有效地把二者的测量数据融合到同一个坐标系中,从而实现了高精度三维测量。分两种情况讨论了靶丸装配误差的检测方法。实验结果验证了这两种方法的可行性,并比较了两种方法的测量精度,其极限测量误差均不超过3 m。     

Chirality of molecular nanostructures on surfaces via molecular assembly and reaction: manifestation and control

The formation of chiral nanostructures via molecular assembly and reaction on solid surfaces is a ubiquitous surface process due to the symmetry-breaking at 2D surface. Studying chirality during the adsorption, assembly, and reaction of molecules on 2D solid surfaces at molecular level not only sheds deep insights into the enantioselective heterogeneous catalysis, chiral recognition, origin and evolution of chirality, and many important physical chemistry processes but also provides an important strategy to create chiral nanostructures. Here, we give a survey of recent advances in chiral expression and control in molecular assemblies and reactions on surfaces. We firstly give a brief introduction to the general concepts of chiral molecular nanostructures on surfaces. And then we focus on the induction and control of chirality expressed in molecular assemblies. The recent developments in the control strategies such as chiral co-adsorber, chiral auxiliary, chiral solvent, chiral templated surfaces, as well as the underlying mechanism to achieve the chiral induction and amplification, are reviewed. After that, we review the studies of chirality expressed in on-surface synthesis which has been proved to be a promising strategy to fabricate covalently bonded low-dimensional nanostructures and materials. In this respect, we introduce the chiral expression in the intramolecular and intermolecular coupling reactions on surfaces. In addition, we survey the methods to steer the stereoselectivity of on-surface reactions including the design of precursor structure, steric hindrance effect, substrate, kinetic parameters et al. Finally, the future outlook in this field is discussed.     

Electronic structure of platinum at ultrahigh pressure

Abstract

Platinum is studied, theoretically, under very high compression. The calculated equation of state is found to agree well with the recent experimental data. At V/V₀ = 0.4, where V₀ is the experimental equilibrium volume, we find a transition from the face centered cubic structure (fcc), found at ambient pressure, to the body centered cubic structure (bcc). The calculated transition pressure is 26 Mbar. The stabilization of the bcc structure is explained by the eigen value sum.     

基于像差特征分析的变焦光学系统装调

提出了一种基于像差特征分析的变焦系统共轴性装调方法。针对某型20倍变焦光学系统的装调,在分析变焦光学系统装调要求的基础上,通过采用光学定心加工技术,提高变焦系统各镜组内光学元件的同轴度;采用Zygo干涉仪,检测变焦系统在长短焦位置的像差特性分布;借助CodeV软件仿真计算各光学元件在系统中的公差灵敏度分布,并确定产生像差影响的敏感光学元件;在中心偏测量仪上,完成最终光学系统像质的调整。此外,还设计了一种变焦光学系统各动组间同轴度调试装置,对变焦相机主镜筒机械内孔轴线与直线导轨的平行性进行了精确测量,保证了动组组元光轴的同轴精度。装调结果表明:变焦系统成像质量有明显改善,像面一致性得到保证,长短焦轴上传递函数值分别优于技术要求值0.45和0.55,长短焦轴外0.7视场传递函数值优于0.25和0.35,实现了高精度装调,验证了该方法的可靠性。     

光突发交换网络中最长队列优先调度组装机制

提出了光突发交换网络中的最长队列优先调度（LQF-SA）机制,将边缘节点的突发组装和突发调度两种技术紧密结合在一起.在现实网络中,业务通常是非均匀分布的,即在某些源宿对之间存在更大的业务流量.仿真结果表明,LQF-SA机制可以很好地完成非均匀分布业务流的组装.即使在均匀分布业务流输入下,LQF-SA机制在突发大小分布、组装效率和突发丢失率等方面也优于已提出的轮询调度组装（RR-SA）机制.     

C-Fe chains due to segregated carbon impurities on Fe(1 0 0)

Bulk carbon impurities segregate at the Fe(1 0 0) surface and, upon thermal annealing, can form metastable surface phases with local and long range order and peculiar electronic properties. We present a surface science study of C-segregated Fe(1 0 0) with scanning tunneling microscopy, angle resolved photoemission, and ab initio calculations of the surface structure and electron states. In particular the c(3√2 × √2) structure, observed for 0.67 atomic layers of C segregated at the iron surface, is found to be due to self-organized carbon stripes made of zig-zag chains. The strong hybridization between C and Fe was observed in ARPES spectra.     

苝二酸酐与嘧啶衍生物的氢键组装

用半经验AM1方法对苝二酸酐与嘧啶衍生物的1:1及1:2氢键复合物进行理论研究,表明随着氢键数目增多,弱相互作用能变大,主体上的供电基和客体上的吸电基有利于氢键相互作用,氢键导致电子从主体流向客体.用INDO/SCI方法计算配合物的电子光谱,表明其长波吸收峰与主体相比发生兰移,各配合物的长波吸收峰位置相差不大,与实验一致.讨论吸收峰兰移的原因并对电子跃迁进行理论指认,同时得到了配合物的双质子转移势能曲线,给出了相对于N-H键的过渡态和活化能.     

六面顶压机高压腔体温度场的数值模拟

 以有限元法为分析手段,在模型和边界条件适当简化的条件下,对六面顶压机高压腔体的温度场进行了数值模拟计算,得出了腔体内的温度分布。在此基础上通过调整模型参数,定性讨论了样品组装设计中组装材料、加热器形状以及导电金属环厚度对温度场的影响。数值模拟结果表明：用氧化锆替代叶蜡石作为堵头和保温材料可以提高样品区的温度,降低功率的消耗并减小样品区的温度梯度;与圆筒形加热器组装相比,中间厚两端薄的变圆筒形加热器组装能提供更高的样品中心温度和较小的温度梯度;使用导电金属环的加热组装时,适当增加金属环的厚度有利于获得较理想的温度分布。研究结果对优化高压实验的样品组装设计、改善温度梯度及保护设备具有一定的参考价值。