Evolution of Classical and Quantum States in the Groupoid Picture of Quantum Mechanics

The evolution of states of the composition of classical and quantum systems in the groupoid formalism for physical theories introduced recently is discussed. It is shown that the notion of a classical system, in the sense of Birkhoff and von Neumann, is equivalent, in the case of systems with a countable number of outputs, to a totally disconnected groupoid with Abelian von Neumann algebra. The impossibility of evolving a separable state of a composite system made up of a classical and a quantum one into an entangled state by means of a unitary evolution is proven in accordance with Raggio’s theorem, which is extended to include a new family of separable states corresponding to the composition of a system with a totally disconnected space of outcomes and a quantum one.     

Mn2+、N2-共掺杂Zn2GeO4晶体电子结构和光学性质的研究

采用基于密度泛函理论的平面波超软赝势方法对本征Zn2GeO4，Mn2+掺杂Zn2GeO4，Mn2+/N2-共掺杂Zn2GeO4超晶胞进行了几何结构优化，计算了掺杂前后体系的晶格常数、能带结构、态密度和光学性质。结果表明，Mn离子掺入后，Mn离子3d轨道与O离子2p轨道之间有强烈的轨道杂化效应，掺杂系统不稳定，而Mn/N离子共掺后，Mn离子和N离子之间的吸引作用克服了Mn离子之间的排斥作用，能够明显地提高掺杂浓度和体系的稳定性。光学性质计算结果表明，Mn离子与N离子共掺杂能改善Zn2GeO4电子在低能区的光学跃迁特性，增强电子在可见光区的光学跃迁；吸收谱计算结果显示，Mn离子与N离子掺入后体系对低频电磁波吸收增加。     

基于平面度的燃料电池电化学性能模拟

 固体氧化物燃料电池的翘曲会影响电极-盖板界面的接触情况，从而影响电化学性能，对相关制造工艺提出了很大的挑战．为了分析燃料电池平面度对放电过程的影响，揭示其潜在的风险，我们建立了两个基于有限元法的仿真模型，对考虑平面度缺陷的燃料电池封装和放电进行分析．在对固体氧化物燃料电池进行平面度测量的基础上，首先建立了具有真实燃料电池翘曲特性的几何模型，分析封装过程中接触压力的分布情况．然后将接触电阻的仿真结果导入到三维多物理场耦合模型中，模拟具有平面度缺陷的燃料电池电化学性能．计算结果展示了燃料电池两侧封装过程中接触压力的分布情况．通过对比有接触电阻和无接触电阻的燃料电池电流密度，分析了电池与盖板的接触对放电过程的影响．结果表明，燃料电池的凹陷面较难达到满意的接触状态，需要比凸起面更大的封装压力．燃料电池表面接触电阻的变化将引起电流传导路径的变化，产生局部高电流或低电流．这项工作强调了在燃料电池中保持均匀分布的接触电阻的重要性，为今后的优化工作奠定了基础．     

Two-Photon Absorption Enhancement by the Inclusion of a Tropone Ring in Distorted Nanographene Ribbons

A new family of distorted ribbon-shaped nanographenes was designed, synthesized, and their optical and electrochemical properties were evaluated, pointing out an unprecedented correlation between their structural characteristics and the two-photon absorption (TPA) responses and electrochemical band gaps. Three nanographene ribbons have been prepared: a seven-membered-ring-containing nanographene presenting a tropone moiety at the edge, its full-carbon analogue, and a purely hexagonal one. We have found that the TPA cross-sections and the electrochemical band gaps of the seven-membered-ring-containing compounds are higher and lower, respectively, than those of the fully hexagonal polycyclic aromatic hydrocarbon (PAH). Interestingly, the inclusion of additional curvature has a positive effect in terms of non-linear optical properties of those ribbons.     

基于MRS-SJC-Copula模型对A股与港股的动态联动性研究

由于经济增长周期变化,导致不同股票市场存在高低状态转换的现象,在研究不同股票市场之间联动性的研究时,需要考虑股票波动均值和方差两种结构变化。基于具有马尔可夫状态转换的动态SJC-Copula,结合修正ICSS算法对我国内地股票市场和香港股票市场之间的联动性进行方差结构突变点的检验。实证结果表明:国内和香港股票市场之间存在非线性非对称的时变相依性,并持续存在高低两种不同状态的概率转换。股票指数由于动态联动受到负面消息的下跌幅度大于正面消息的变化幅度,且上下尾部均受上期信息的持续影响。“沪港通”、“深港通”、中美贸易战等因素使得其上下尾部发生结构突变,内地与香港股票市场的联动性增大和市场波动幅度趋强。     

微生物燃料电池阴极脱氮

微生物燃料电池(MFC)阴极电子受体的多样性可实现其阴极脱氮,从而将产生的电能合理利用,因此阴极脱氮成为了MFC的一个研究方向,同时也为实际废水中氮素的去除提供了新的可能。然而在反应过程中有众多因素会导致NOx-N与其他电子受体竞争阳极电子的现象,影响阴极反硝化过程对于电子的利用率,从而造成脱氮效率低等现实问题。目前已有许多研究通过优化MFC自身结构弥补产电的缺陷,及将与其他工艺系统耦合实现同步硝化反硝化等方法,取长补短以增加脱氮效率,降低对碳源的需求,以此解决微生物燃料电池阴极脱氮出现的问题。本文从MFC不同的脱氮历程、MFC工艺条件(pH、C/N、DO)、极室分隔材料等影响MFC阴极脱氮的因素及影响其阴极反硝化微生物群落构成等方面,进行了综述并预测未来研究方向。     

Information percolation and cutoff for the random‐cluster model

We consider the random‐cluster model (RCM) on with parameters p∈(0,1) and q ≥ 1. This is a generalization of the standard bond percolation (with edges open independently with probability p) which is biased by a factor q raised to the number of connected components. We study the well‐known Fortuin‐Kasteleyn (FK)‐dynamics on this model where the update at an edge depends on the global geometry of the system unlike the Glauber heat‐bath dynamics for spin systems, and prove that for all small enough p (depending on the dimension) and any q>1, the FK‐dynamics exhibits the cutoff phenomenon at with a window size , where λ_∞ is the large n limit of the spectral gap of the process. Our proof extends the information percolation framework of Lubetzky and Sly to the RCM and also relies on the arguments of Blanca and Sinclair who proved a sharp mixing time bound for the planar version. A key aspect of our proof is the analysis of the effect of a sequence of dependent (across time) Bernoulli percolations extracted from the graphical construction of the dynamics, on how information propagates.