Properties of hybrid stars in an extended MIT bag model

The properties of hybrid stars are investigated in the framework of the relativistic mean field theory （RMFT） and an MIT bag model with density-dependent bag constant to describe the hadron phase （HP） and quark phase （QP）, respectively. We find that the density-dependent B（p） decreases with baryon density p; this decrement makes the strange quark matter become more energetically favorable than ever, which makes the threshold densities of the hadron-quark phase transition lower than those of the original bag constant case. In this case, the hyperon degrees of freedom can not be considered. As a result, the equations of state of a star in the mixed phase （MP） become softer whereas those in the QP become stiffer, and the radii of the star obviously decrease. This indicates that the extended MIT bag model is more suitable to describe hybrid stars with small radii.     

Lattice Boltzmann Simulations of Particle-Particle Interaction in Steady Poiseuille Flow

The moving behaviour of two- and three-particles in a pressure-driven flow is studied by the lattice Boltzmann simulation in two dimensions. The time-dependent values, including particles＇ radial positions, translational velocities, angular velocities, and the x-directional distance between the particles are analysed extensively. The effect of flow Reynolds number on particle motion is also investigated numerically. The simulation results show that the leading particle equilibrium position is closer to the channel centre while the trailing particle equilibrium position is closer to the channel wall. If Reynolds number Re is less than 85.30, the larger flow Reynolds number results in the smaller x-directional equilibrium distance, otherwise the x-directional distance increases almost linearly with the increase of time and the particles separate finally. The simulation results are helpful to understand the particle-particle interaction in suspensions with swarms of particles.     

离散神经网络指数稳定改进条件

研究了一类时滞离散神经网络指数稳定及鲁棒稳定问题.结合线性矩阵不等式技术,构造了一个新的广义李亚普诺夫函数,得到了新的指数稳定条件.数值算例表明与以往文献中的结果相比,新准则具有较弱的保守性.     

基于梯度依赖的非局部摩擦模型的土坡稳定性分析

研究了基于梯度依赖的非局部摩擦模型下圆弧滑裂面土坡的稳定性,并对梯度依赖的非局部材料参数进行讨论与分析,研究了此参数对土坡安全系数的影响,从微观的角度分析宏观工程问题发挥机理的本质,发现带微观性质的非局部材料参数变化时,土坡安全系数变化虽然不大,但变化趋势很明显．当讨论土体相关参数对安全系数的影响时,根据梯度依赖的非局部摩擦模型与局部摩擦模型的对比,发现安全系数对内摩擦角的变化比较敏感,可为工程中土坡治理提供参考依据．     

A time-dependent density functional theory investigation of plasmon resonances of linear Au atomic chains

We report theoretical studies on the plasmon resonances in linear Au atomic chains by using ab initio time-dependent density functional theory. The dipole responses are investigated each as a function of chain length. They converge into a single resonance in the longitudinal mode but split into two transverse modes. As the chain length increases, the longitudinal plasmon mode is redshifted in energy while the transverse modes shift in the opposite direction (blueshifts). In addition, the energy gap between the two transverse modes reduces with chain length increasing. We find that there are unique characteristics, different from those of other metallic chains. These characteristics are crucial to atomic-scale engineering of single-molecule sensing, optical spectroscopy, and so on.     

不对称反应的对映体过量值预测

建立了手性催化剂结构与反应产物对映体过量值的定量结构-活性相关性模型, 以辅助苯乙酮不对称氢转移反应的催化剂筛选. 手性催化剂由手性氨醇配体与金属络合物合成, 故采用构象独立手性指数或构象依赖手性指数描述手性氨醇配体, 采用指示变量区分金属络合物, 然后合并2个指数来描述手性催化剂. 通过遗传算法进行变量选择, 采用随机森林法建立数学模型以预测对映体过量值, 测试集的相关系数R²=0.769, 整个数据集的OOB(Out-of-bag)交叉验证结果为R²=0.785.     

不同类型旅游移民的地方认同建构研究——以丽江古城为例

旅游移民在国内已经出现,却很少得到学者的关注.以丽江古城为例,通过修正后的量表对丽江古城的旅游移民进行实测.然后通过SPSS 20.0软件,综合运用独立样本T检验、单因素分析法对不同类型旅游移民的地方认同水平及影响因素做了分析.再将人口统计学特征、"城市融入""外出目的"依次投入模型进行阶层回归分析.研究发现:(1)不同类型旅游移民的地方认同的影响机制不同,生活方式型旅游移民对丽江的地方认同显著高于经济利益导向型旅游移民;(2)地方认同不存在"性别"差异,"居住时间"和"从事行业"显著影响生活方式型旅游移民的地方认同;(3)总体而言,"城市融入"对于旅游移民地方认同的解释力度要高于"外出目的",其中"是否与当地居民来往"仅对经济利益导向型旅游移民产生影响.研究丰富了旅游移民的人地关系研究,对于旅游地的可持续发展也具有一定的现实意义.     

Current Density-Dependent Thermal Stability of ZnSe Nanowire in M-S-M NanostructureD

Due to semiconductor nanowire （NW） having a very tiny diameter, the electronic devices based on metal-semiconductor NW-metal （M-S-M） nanostruc- ture can carry a very large current density com- pared to electronics based on bulk semiconductors. A small mass of a NW also means a small heat capacitance. In this case, any small energy trans- fer from the current-carry electrons to local ionic or/and lattice vibrations in NWs may cause a sub- stantial self-heating of the NWs. Thus thermal insta- bility of NWs in M-S-M nanostructure due to Joule heating has become a fundamentally and technolog- ically important issue concerning the performance of semiconductor NW-based nanoelectronics and has at- tracted a lot of attention. The failure behaviors of various semiconductor and metallic NWs inves- tigated by in situ transmission electron microscopy （TEM） and confocal micro-Raman spectroscopy re- spectively have confirmed semiconductor NWs includ- ing Si, Ge, GaN, ZnO, Sn02, Ti02, ZnSe and ZnTe NWs electrically broken by thermal evaporation due to Joule heating and metallic NWs electrically de- stroyed by electromigration. Electron-phonon in- teraction that transfers energy from conduction elec- trons to the ions in the material causes Joule heating. Electromigration due to the transfer of the momentum of conduction electrons to the ions causes migration of atoms in the material when high current density flows through a circuit. The different failure mechanisms of these NWs are significantly materials-dependent due to the difference of their chemical and physical prop- erties and have a very close relation with the param- eters governing the electron transport mechanism at the metal-semiconductor （M-S） nanocontact such as Schottky barrier and bias polarity .     

光激活磁共振脑功能成像的研究现状及前景

磁共振脑功能成像经过20年的发展已经成为大脑认知神经科学研究中最主要的技术.光激活磁共振脑功能成像是将它与新发展起来的光遗传学相结合的新兴技术,具有高时空选择性地分析特定神经回路或特定类型的神经元在整个功能网络中的作用的巨大潜力,为理解人类脑功能和揭示神经精神疾病机理可提供新的技术手段.     

与双模场依赖强度耦合下多光子通道中原子比 特周期量子回声产生和调控

旋波近似条件下,运用全量子理论研究了与双模相干光场依赖强度耦合多光子通道中原子比特周期量子回声的产生和控制. 采用数值计算的方法,讨论了双模相干光场平均光子数分布形式、分布范围及原子跃迁时吸收(或发射)的光子数k对原子比特态保真度演化的影响,获得了产生和控制原子比特周期量子回声的系统参量;根据纠缠理论,分析了原子比特态保真度演化与原子约化熵演化的关联. 结果表明:在k=1的双光子过程中,调控光场平均光子数呈对称或不对称分布,当它的取值在一定范围内,原子比特保持良好的相干性和保真度,产生周期量子回声; 对于k≥2的多光子过程,原子比特与双模相干光场始终处于最大纠缠,因此导致了原子比特始终处于部分失真状态,不产生周期量子回声. 本研究揭示了周期量子回声产生的物理实质是原子比特与光场周期性退纠缠.