Theoretical study of stabilities,electronic, and catalytic performance of supported platinum on modified graphene

The geometry, electronic structure, and catalytic properties for CO oxidation of Pt atom supported on pri-graphene (PG), Haeckelite (H), and Stone–Wales-defect-graphene are investigated by density functional theory (DFT) calculations. In contrast to a Pt atom on PG, defective graphene, especially the Haeckelite, strongly stabilises the Pt atom and makes it more positive and thus the CO poisoning. At the same time the catalytic activities are as high as the pristine one. Langmuir–Hinshelwood mechanisms are favoured as the starting state and are followed by the Eley–Rideal reaction. The results indicate the benefit of Haeckelite as a substrate for the Pt atom and validate the reactivity of catalysts on the atomic scale with low cost and high activity.     

ZnAl2O4：Tb3+荧光粉的合成、结构及其光学性能研究

通过溶胶-凝胶法制备出不同Tb³⁺掺杂浓度和不同二次煅烧温度下的ZnAl₂O₄:Tb³⁺荧光粉, 并利用X射线衍射(XRD)和荧光光谱等对样品进行了表征。由XRD结果可知,当Tb³⁺掺杂的摩尔分数不大于9%,二次煅烧温度在600℃以上时,所得粉体为结晶性良好的尖晶石相。在紫外光激发下,ZnAl₂O₄:Tb³⁺荧光粉的发射光谱由位于488 nm(⁵D₄→⁷F₆)、542 nm(⁵D₄→⁷F₅)、587 nm(⁵D₄→⁷F₄ )和621.5 nm(⁵D₄→⁷F₃)的4个发射峰组成。研究发现,Tb³⁺的掺杂浓度和二次煅烧温度对样品发光强度有着重要影响,当Tb³⁺的摩尔分数为5%,二次煅烧温度为900℃时,ZnAl₂O₄:Tb³⁺荧光粉的发光最强,继续增加Tb³⁺掺杂浓度或提高煅烧温度,分别会出现浓度猝灭和温度猝灭现象。     

强流ECR离子源引出系统研究

为了提高强流ECR 离子源的引出束流品质,分别设计了1# 和2# 引出系统,利用束流引出模拟软件PBGUNS 对1# 和2# 引出系统进行了质子束流引出与传输的模拟计算,结合实际测得的发射度数据分析引出系统,发现2# 引出系统比1# 引出系统引出束流品质高。对ECR 离子源引出系统的电势等位线分布等参数引起的球差进行了简单数学推导及MATLAB 绘图,并结合1# 和2# 引出系统束流相图模拟结果证明了球差会使引出束流品质有效发射度增长,通过适当加大电极孔径可改善束流聚焦情况,得到了束流光学聚焦较好的束流引出系统设计。To improve the quality of extracted ion beam from a high current ECR ion source, 1# and 2# extraction systems were designed and tested. The PBGUNS code was used to simulate the 1# and 2# extraction systems of proton ion beam. The emittance measurement results with the two different extraction systems were compared and analyzed with the simulation, the conclusion that more high quality beam extracted from 2# system than 1# system was got. The formula derivation of ECR ion source extraction system spherical aberration and MATLAB drawing was done by the analyzing on the distribution of extraction field equipotentials, effective emittance increasing caused by spherical berration was proved by 1# and 2# extraction systems beam phase space simulation result, beam focusing would be improved if electrode hole size increasing appropriately and a general concept on good optics focusing of ion beam extraction system was proposed finally.     

Quantum anomalous Hall effect and related topological electronic states

Over a long period of exploration, the successful observation of quantized version of anomalous Hall effect (AHE) in thin film of magnetically doped topological insulator (TI) completed a quantum Hall trio—quantum Hall effect (QHE), quantum spin Hall effect (QSHE), and quantum anomalous Hall effect (QAHE). On the theoretical front, it was understood that the intrinsic AHE is related to Berry curvature and U(1) gauge field in momentum space. This understanding established connection between the QAHE and the topological properties of electronic structures characterized by the Chern number. With the time-reversal symmetry (TRS) broken by magnetization, a QAHE system carries dissipationless charge current at edges, similar to the QHE where an external magnetic field is necessary. The QAHE and corresponding Chern insulators are also closely related to other topological electronic states, such as TIs and topological semimetals, which have been extensively studied recently and have been known to exist in various compounds. First-principles electronic structure calculations play important roles not only for the understanding of fundamental physics in this field, but also towards the prediction and realization of realistic compounds. In this article, a theoretical review on the Berry phase mechanism and related topological electronic states in terms of various topological invariants will be given with focus on the QAHE and Chern insulators. We will introduce the Wilson loop method and the band inversion mechanism for the selection and design of topological materials, and discuss the predictive power of first-principles calculations. Finally, remaining issues, challenges and possible applications for future investigations in the field will be addressed.     

电磁迴旋不稳定性的准线性理论

在有弱相对论性电子时,在电子迴旋频率Ω_e附近存在快x模的不稳定性。从这一事实出发,我们用准线性理论分析了具有粒子数倒转的分布函数引起的不稳定性最后达到饱和的物理机制。进行了一些近似的计算,求出了电磁迴旋不稳定性的饱和时间和饱和能量及垂直、平行分布函数随时间的演化过程。发现用此理论算出的饱和能级与观察到的AKR结果是一致的。 关键词：     

McMillan Tc公式的解析推导(Ⅲ)

本文把作者在前面两篇文章导出的T_c公式推广成下面形式:T_c=αω_log(ω_log/ω_c)^{(μ*/(λ-μ*))exp{-(1+λ)/(λ-μ*)},并从线性Eliashberg方程出发,导出了计算α的方程组。α一般是λ和μ*的函数。在弱耦合极限下,由上述方程组解得,α=2γ/π,其中lnγ=C=0.5772是Euler常数。这个结果表明了,前面两篇文章得到的T_c公式在弱耦合极限下是正确的。作者进而在Einstein谱和μ*=0情形,用数值计算方法从定α的方程组算出当λ=0.23,0.25,0.38和0.48时,a的数值。结果表明,至少在0.23≤λ≤0.45区间中,α变化很小,近似等于1/1.30。此时,本文的T_c公式实际上就是Allen及Dynes修改后的经验的McMillan T_c公式。 关键词：}     

纳米金属氧化物：复合分散法制备及分散性

通过采用水热晶化与荷电复合分散法制备γ-AlOOH、R-TiO₂和α-Al₂O₃纳米晶体粉末,利用TEM和激光粒度分析仪等手段研究了纳米颗粒水热晶化与荷电复合分散的分散效果及其工艺条件,并探讨了金属氧化物纳米颗粒水热晶化与荷电复合分散机理。结果表明,晶化与荷电复合分散可明显改善金属氧化物纳米颗粒在液相中的分散稳定性,所制得的AlOOH、TiO₂和Al₂O₃纳米颗粒在水中分散放置24 h后的透光率的变化率D₂₄还可分别保持为94.1%、87.7%和82.2%;在水中分散后的粒径分布统计的平均粒径分别为67、70和143 nm。     

基于流函数模型的矢量海流生成方法

提出了一种基于海洋流函数模型的双站高频地波雷达径向流生成矢量流算法.该算法避免了传统矢量合成法将径向流进行插值带来的误差,而且符合海洋动力学原理,生成的流场更接近实际分布.通过计算机仿真发现,流函数算法的容错、容差能力比矢量合成法更强.在径向流探测标准误差为10 cm.s-1时,新算法反演结果的均方根误差减小了约5 cm.s-1.应用到雷达实测数据中,与海流计实测结果比较表明,新算法比传统算法的平均误差减小了2 cm.s-1.     

暗腹雪鸡细胞色素b基因的克隆及其在雉科中亲缘关系的分析

用聚合酶链式反应克隆暗腹雪鸡(Tetraogallus himalayensis)Cyt b基因,首次报道该基因的全长序列(1143bp AY678108),并与雉科中其他19个属的Cyt b基因进行同源性比较,分析了碱基组成和变异情况.用邻接法、最大简约法和最大拟然法构建了系统进化树,得到了基本相同的拓扑结构.结果表明雪鸡属与鹌鹑属、石鸡属的亲缘关系最近,形成单系群.雪鸡属与鹌鹑属的分歧时间为1.5～2.0百万年,与石鸡属分歧时间为1.7～2.4百万年.     

几丁质发酵液的生物活性

鞘氨醇单胞菌CJ-5菌株在以几丁质为碳源的培养基上生长,既产生几丁质酶又产生壳聚糖酶.利用其发酵液进行抑制真菌,促进植物生长等生物活性的研究及作用机理的探讨,发现CJ-5菌株的几丁质发酵液具有抑制番茄枯萎病菌,促进水稻扩叶生根的效果,显示了潜在的防治植物病原菌及促进植物生长的能力.