Loop statistics in complex networks

We study a scaling property of the number M_h(N) of loops of size h in complex networks with respect to a network size N. For networks with a bounded second moment of degree, we find two distinct scaling behaviors: M_h(N) ~ (constant) and M_h(N) ~ lnN as N increases. Uncorrelated random networks specified only with a degree distribution and Markovian networks specified only with a nearest neighbor degree-degree correlation display the former scaling behavior, while growing network models display the latter. The difference is attributed to structural correlation that cannot be captured by a short-range degree-degree correlation.     

Equilibrium shape and size of supported heteroepitaxial nanoislands

We study the equilibrium shape, shape transitions and optimal size of strained heteroepitaxial nanoislands with a two-dimensional atomistic model using simply adjustable interatomic pair potentials. We map out the global phase diagram as a function of substrate-adsorbate misfit and interaction. This phase diagram reveals all the phases corresponding to different well-known growth modes. In particular, for large enough misfits and attractive substrate there is a Stranski-Krastanow regime, where nano-sized islands grow on top of wetting films. We analyze the various terms contributing to the total island energy in detail, and show how the competition between them leads to the optimal shape and size of the islands. Finally, we also develop an analytic interpolation formula for the various contributions to the total energy of strained nanoislands.     

应用Voting Machine构建研究型、互动型的双语物理课堂的研究与实践

高等教育"质量工程"的实施为高等学校本科教学提出了更新、更高的要求和挑战.本文报道了应用Voting Machine这一具有强大的互动和统计功能的教学设备在双语物理课堂上开展研究型、互动型教学的实践和研究成果.     

一道物理实验设计选题的两种实验验证

对一道运用常规思维无法解决的物理实验设计选题,从转动惯量和发声音调两个视角给出了实验方案及实验验证.     

La0．5Er0．2Ca0．3Mno3低温磁电阻效应的实验研究

本文简要介绍对La0．5Er0．2Ca0．3Mno3进行低温电磁测量的实验过程,研究掺杂后复合体系的磁电阻效应。     

Elastic theory of defects in toroidal crystals

We report a comprehensive analysis of the ground-state properties of axisymmetric toroidal crystals based on the elastic theory of defects on curved substrates. The ground state is analyzed as a function of the aspect ratio of the torus, which provides a non-local measure of the underlying Gaussian curvature, and the ratio of the defect core energy to the Young modulus. Several structural features are discussed, including a spectacular example of curvature-driven amorphization in the limit of the aspect ratio approaching one. The outcome of the elastic theory is then compared with the results of a numerical study of a system of point-like particles constrained on the surface of a torus and interacting via a short-range potential. Electronic supplementary material  Supplementary material in the form of a pdf file available from the journal web page at and are accessible for authorised users.     

Analytical calculation of eigen-energies for lens-shaped quantum dot with finite barriers

With the help of metadynamics it is possible to calculate efficiently the free energy of systems displaying high energy barriers as a function of few selected “collective variables”. In doing this, the contribution of all the other degrees of freedom (“microscopic” variables) is averaged out and, thus, lost. In the following it is shown that it is possible to calculate the thermal average of these microscopic degrees of freedom during the metadynamics, not loosing this piece of information. The method is tested on a two-dimensional toy system and on a small molecule, that is dialanine.     

一种新颖的实现冷原子或冷分子囚禁的可控制光学四阱及其二维光学晶格

原子光学晶格为精确操控中性原子和研究某些基本物理问题提供了一种方法。提出了一种利用单光束照明余弦型振幅光栅与透镜组合系统实现冷原子或冷分子囚禁的可控制光学四阱新方案,计算了四阱的光强分布,讨论了从光学四阱到双阱或单阱的演化过程,并导出了光学四阱的几何参量、光强分布、强度梯度及其曲率与光学透镜系统参量间的解析关系,获得了四阱间距与光栅空间频率的关系。研究表明通过改变余弦光栅的空间频率即可实现从光学四阱到双阱或单阱的连续双向演化。     

有机光伏研究进展

以有机半导体材料为活性层的有机太阳能电池, 可通过印刷制备大面积柔性器件, 具有成本低、多彩、半透明等特点, 是一种极具发展前景的光伏技术. 研究者们多年来致力于设计高性能光伏材料, 优化器件界面, 改善活性层微观形貌, 开发新型器件结构, 探究器件工作机理等, 目前实验室制备的小面积有机太阳能电池的能量转换效率已经超过18%. 另外, 面向有机光伏产业化, 在制备大面积柔性器件、降低器件成本、提高器件寿命以及探究光伏建筑一体化和室内光伏等潜在应用方面的研究也取得了重要进展, 在国际上处于领跑地位. 中国科学家在有机光伏领域做出了诸多开创性和引领性的工作. 本文首先对有机太阳能电池的背景进行简单介绍, 接着按照分子工程、器件工程、器件物理和应用探索四个方面综述有机光伏领域的重要研究进展, 最后对有机光伏所面临的机遇与挑战进行展望.     

对2道高考化学模拟试题命制过程的解读与思考

在新课程标准和高考评价体系的背景下,如何提高化学学科的命题质量？通过以学术探索情境为载体命制选择题和以实验探究情境为载体命制非选择题的2例,展示了在双向细目表的指引下,检索文献、初拟试题、打磨试题和要素分析的过程,剖析了精炼试题语言表述、核实信息来源、优化信息呈现方式和调整测试任务的各环节,总结了依靠团队合作精心筛选命题素材、创设真实问题情境、科学设计测试任务、反复推敲打磨试题的命题经验。