同步辐射讲座第一讲 同步辐射XAFS实验站及其应用

介绍了北京和合肥同步辐射XAFS实验站的性能参数和结构, 及在物理，化学，材料和生命科学等研究领域的应用，便于国内广大用户更好地利用其开展高质量的研究工作。     

Synthesis, Characterization, Spectroscopic Properties of 2-（4-Dimethylaminophenyl）-5-fluoro-6-（morpholin-4-yl）-1H-benzimidazole and its Interaction with Calf Thymus DNA

Benzimidazole compounds have attracted a renewed interest recently owing to theirpotential applications in high-performance composite materials, electronic chemicals,photosensitive materials, and their special potentials in biological and/or medicinalapplication1,2. Typically, aromatic compounds with near planar structures and contain-ing hydrogen-donor groups or groups, which are capable of being protonated, havespecial interactions with DNA via intercalation, hydrogen-bonding, and so on3.Me…     

p-adic Transcendence and p-adic Transcendence Measures for the Values of Mahler Type Functions

We prove the p-adic transcendence and p-adic transcendence measures for the values of some Mahler type functions.     

Study on the microstructure and wear resistance of the composite coatings fabricated on Ti-6Al-4V under different processing conditions

Composite coatings mainly containing titanium carbides and borides were produced by laser surface alloying of Ti-6Al-4V with graphite and boron mixed powders. The test results show that the coatings have higher hardness (1600-1700 HV_0.1) and are more resistant to wear than the as-received sample. Laser scanning speed and the content of alloying elements (weight ratio of graphite to boron) have an effect on both the microstructure and the wear resistance of the coatings. TEM results show that strip titanium carbides and borides grow alternately and thus restrain the formation of coarse needle-like TiB and dendritic TiC crystals produced by laser alloying of titanium alloys with boron and graphite separately.     

Quantum spin correlations in an organometallic alternating-sign chain

High resolution neutron scattering is used to study excitations in the organometallic magnet (CH3)2NH2CuCl3 (DMACuCl3). Combined with bulk magnetization and susceptibility studies, the new results imply that DMACuCl3 is a realization of the S=1/2 alternating antiferromagnetic-ferromagnetic (AFM-FM) chain. Coupled-cluster calculations indicate that the AFM and FM interactions have nearly the same strength, while analysis of scattering intensities shows evidence for interdimer spin correlations. Results are discussed in the context of recent ideas concerning quantum entanglement.     

Edge-emitting photonic crystal double-heterostructure nanocavity lasers with InAs quantum dot active material

We report what is, to the best of our knowledge, the first demonstration of an edge-emitting photonic crystal nanocavity laser that is integrated with a photonic crystal waveguide. This demonstration is achieved with a double-heterostructure photonic crystal nanocavity incorporating an InAs quantum dot active region.     

Refractive indices of biaxial crystals evaluated from the refractive indices ellipsoid equation

The expressions of the refractive indices corresponding wave vector k(θ,) are given by using coordinate transformations for the refractive indices ellipsoid equation of biaxial crystals. The refractive index expression of the wave, whose velocity is slower, is given by

and that of the wave, whose velocity is faster, is given by

     

NO dissociation pathways on Rh(1 0 0), (1 1 0), and (1 1 1) surfaces: A comparative density functional theory study

The chemisorption and dissociation pathways of NO on the Rh(1 0 0), (1 1 0), and (1 1 1) surfaces are studied by the plane-wave density functional theory (DFT) with CASTEP program. In addition, the electronic and geometrical effects that affect the NO dissociation reactions have been investigated in detail. The calculation results are presented as following: The effective activation energies of the best NO dissociation pathways on the Rh(1 0 0), the Rh(1 1 0), and the Rh(1 1 1) are 0.63, 0.66 and 1.77 eV, respectively. The activity of the Rh planes for NO dissociation is in the order of Rh(1 0 0) ≈ Rh(1 1 0) > Rh(1 1 1). The low dissociation barrier for Rh(1 0 0) and Rh(1 1 0) is associated with the existence of a lying-down NO structure which acts as a precursor for dissociation. By Mulliken population analysis and structure analysis, both electronic and geometrical effects are found to affect the NO dissociation reactions, but the geometrical effect exceed the electronic. The energy decomposition scheme has been used to provide further insight into the NO dissociation reactions. Based on the calculations, the interaction energy between N and O in the transition state on the Rh(1 1 1) is found much larger than that on the Rh(1 0 0) and the Rh(1 1 0). The major differences of should originate from the variation of the bonding competition effect.     

Two-Phase Image Segmentation by Nonconvex Nonsmooth Models with Convergent Alternating Minimization Algorithms

Two-phase image segmentation is a fundamental task to partition an image into foreground and background. In this paper, two types of nonconvex and nonsmooth regularization models are proposed for basic two-phase segmentation. They extend the convex regularization on the characteristic function on the image domain to the nonconvex case, which are able to better obtain piecewise constant regions with neat boundaries. By analyzing the proposed non-Lipschitz model, we combine the proximal alternating minimization framework with support shrinkage and linearization strategies to design our algorithm. This leads to two alternating strongly convex subproblems which can be easily solved. Similarly, we present an algorithm without support shrinkage operation for the nonconvex Lipschitz case. Using the Kurdyka-Łojasiewicz property of the objective function, we prove that the limit point of the generated sequence is a critical point of the original nonconvex nonsmooth problem. Numerical experiments and comparisons illustrate the effectiveness of our method in two-phase image segmentation.     

双重网络嵌入对公司IPO后市场表现的影响研究

将社会网络嵌入理论从单一网络拓展至双重网络,分析上市公司同时嵌入风险投资网络和承销商网络对公司IPO上市后市场表现的影响。利用2004～2017年有风险投资支持的IPO公司数据,实证检验结果表明：(1)单独嵌入风险投资网络中心位置、单独嵌入承销商网络中心位置,均会提高公司IPO后市场表现;(2)同时嵌入风险投资网络中心位置和承销商网络中心位置,对公司IPO后短期市场表现的正向影响会相互替代;(3)同时嵌入风险投资网络中心位置和承销商网络中心位置,对公司IPO后长期市场表现的正向影响会互相补充。