Clustering in the Three and Four Color Cyclic Particle Systems in One Dimension

We study the \(\kappa \)-color cyclic particle system on the one-dimensional integer lattice \(\mathbb {Z}\), first introduced by Bramson and Griffeath (Ann Prob:26–45, 1989). In that paper they show that almost surely, every site changes its color infinitely often if \(\kappa \in \{3,4\}\) and only finitely many times if \(\kappa \ge 5\). In addition, they conjecture that for \(\kappa \in \{3,4\}\) the system clusters, that is, for any pair of sites x, y, with probability tending to 1 as \(t\rightarrow \infty \), x and y have the same color at time t. Here we prove that conjecture.     

不同类型偶氮材料光致双折射的温度特性研究

在不同温度下,分别测量了掺杂偶氮材料、偶氮聚合物和偶氮液晶聚合物的光致双折射行为,并利用双e指数模型对光致双折射的动力学过程进行了拟合.实验结果表明,偶氮材料的光致双折射源于偶氮分子的光致异构和光致分子取向,光致双折射大小随温度的升高表现出先增大后减小的趋势.在抽运光的作用下,含偶氮材料的光致双折射包含一个由偶氮分子取向引起的快过程和一个由偶氮分子带动大分子取向引起的慢过程.关闭抽运光后,掺杂偶氮材料和偶氮聚合物表现为可逆的弛豫,而偶氮液晶聚合物则展现出长久光存储特性.     

Synthesis and Crystal Structure of a Mixed-Ligand Cobalt(II) Complex with 2-Aminobenzimidazole

Abstract  The cobalt(II) complex, [Co(abz)₂(SCN)₂] 1, has been synthesized by the reaction of cobalt(II) nitrate with ammonium thiocyanate and abz ligands (abz = 2-aminobenzimidazole), and was fully structurally characterized by elemental analysis, IR spectra, X-ray diffraction and thermogravimetric experiments. It crystallizes in the triclinic P-1 space group with a = 8.6316(10), b = 9.3426(10), c = 13.254(2) ?, α = 95.793(2), β = 95.870(2), γ = 115.7380(10), V = 945.1(2) ?³, and Z = 2. The central cobalt(II) atom is four-coordinated to nitrogen donors from two neutral abz ligands and two isothiocyanate anions respectively, adopting a slightly distorted tetrahedral geometry. In addition, the intermolecular N–H···N and N–H···S hydrogen bonds interactions link the discrete mononuclear units into infinite three-dimensional networks. Index Abstract  The essence sentence of the paper: In the mixed-ligand mononuclear complex, [Co(abz)₂(SCN)₂], the four coordinated cobalt(II) atom exhibits a slightly distort tetrahedron, which is further assembled into 3D infinite network by intermolecular hydrogen interactions.      

高倍率锂离子电池负极材料:氮掺杂碳纳米笼

锂离子电池具有能量密度高和循环性好等优点, 广泛应用于小型移动设备等领域, 但尚不能满足需要兼具高容量和高倍率性能的应用要求. 以兼具高比表面积、氮含量高且可调、良好石墨化程度、多尺度分级结构(含孔结构)、有微孔通道的寡层笼壁结构等特征的氮掺杂碳纳米笼(NCNC)为锂离子电池负极材料, 展现出高的比容量、优异的倍率性能和稳定性, 譬如: 在0.1 A·g^-1小电流密度下, NCNC800的循环稳定的充电比容量可以高达约900 mAh·g^-1, 显著优于商业石墨; 在20.0 A·g^-1大电流密度下, 循环500圈后的可逆比容量仍能稳定在约135 mAh·g^-1. 如此优异的电化学性能可归因于NCNC的结构特征, 如高比表面积、良好石墨化程度、独特介观结构和孔结构, 这些特征有利于锂离子传输、电解液渗透和电子传导等. 这为开发高倍率和高比容量的锂离子电池负极材料提供思路.     

Role of oxygen functional groups for structure and dynamics of interfacial water on low rank coal surface: a molecular dynamics simulation

Molecular dynamics simulations were employed to study the effects of oxygen functional groups for structure and dynamics properties of interfacial water molecules on the subbituminous coal surface. Because of complex composition and structure, the graphite surface modified by hydroxyl, carboxyl and carbonyl groups was used to represent the surface model of subbituminous coal according to XPS results, and the composing proportion for hydroxyl, carbonyl and carboxyl is 25:3:5. The hydration energy with ?386.28 kJ/mol means that the adsorption process between water and coal surface is spontaneous. Density profiles for oxygen atoms and hydrogen atoms indicate that the coal surface properties affect the structural and dynamic characteristics of the interfacial water molecules. The interfacial water exhibits much more ordering than bulk water. The results of radial distribution functions, mean square displacement and local self-diffusion coefficient for water molecule related to three oxygen moieties confirmed that the water molecules prefer to absorb with carboxylic groups, and adsorption of water molecules at the hydroxyl and carbonyl is similar.     

高氯钻井废水低COD分析方法改进

用重铬酸钾法测定油气田高氯低COD的钻井废水时会产生较大误差。对该国标法测定COD进行了改进,采用低浓度氧化剂,增加硫酸汞以掩蔽氯离子来降低COD的分析误差。实验结果表明,选择0.0500 mol/L的重铬酸钾溶液,硫酸汞与氯质量比为10︰1时,测定结果的相对误差小于10%,适合测定高氯低COD钻井废水的COD值。该方法扩大了国标法的适用范围。     

基于光压原理的大功率激光功率测量北大核心CSCD

大功率激光功率测量常用量热法,但溯源复杂。介绍了具有较高测量精度的基于光压原理的大功率激光功率测量方法,设计了利用1/10^(5)精度天平大功率激光测量实验,测试了基于GaAs半导体材料制作的反射镜的反射率及损伤阈值,确定了基于GaAs半导体材料反射镜的相关性能。得到了普通实验室条件下的功率测量重复性及线性,验证了1/10^(5)精度天平用于大功率激光测量的可行性。通过实验结果结合理论计算,得出利用1/10^(5)精度天平的光压测量功率的测量上限可以达到3×10^(4)W以上。     

肖特基钙钛矿太阳电池结构设计与优化

有机-无机杂化钙钛矿材料有高吸收系数、低廉的制作成本以及较为简单的制备工艺,在近年来表现出良好的发展前景.本文采用wx-AMPS模拟软件对平面结构钙钛矿太阳电池和肖特基钙钛矿太阳电池进行建模仿真对比,从理论上分析无载流子传输层的肖特基钙钛矿太阳电池的优势.结果显示,器件两侧电极功函数和吸收层的能带分布是提高太阳电池效率的关键.在对电极使用Au(功函数为5.1 eV)的前提下,透明导电电极功函数为3.8 eV,可以得到肖特基钙钛矿太阳电池转换效率为17.93%.对器件模型吸收层进行优化,通过寻找合适的掺杂浓度,抑制缺陷密度,确定合适的厚度,可以获得理想的转换效率(20.01%),是平面异质结结构(理论转换效率31%)的63.84%.肖特基钙钛矿太阳电池在简单的器件结构下可以获得优异的光电性能,具有较好的应用潜力.