中国报纸出版业区域发展不均衡性的计量分析

依我国各省(市、自治区)报纸种数、报纸总印数和报纸总印张数等三个指标1986-2006年的数据,构建这一时期各指标相对熵的时间序列。应用ADF检验求时间序列单整阶数并做出分析,应用方向数据统计探讨报纸总印张数相对熵的周期变化。     

Controlled construction of nanostructures in graphene

We report on the laser-assisted fabrications of nanostructures in graphene membranes supported on polymer films. By using a laser beam to deposit heat locally, irradiated polymer instantaneously melts and vaporizes. During laser drilling of the polymer, the single-layer graphene membrane adheres to the polymer surface and consequently forms tens of nanometer deep wells. Due to the short time scale of laser irradiation, heat diffusion in the polymer is negligible, and the excitation energy is highly confined in the polymer. As a result, graphene nanowells of hundreds of nanometers in diameter can be pat- terned with high fidelity. With the increasing of nanowell density, we observe the spontaneous formation of nanowrinkles connecting pairs of nanowells in the graphene membranes. Importantly, Raman spectra confirm that no defects are intro- duced in graphene membranes by laser irradiation under our experimental conditions. Our results highlight the possibility to construct nanostructures and to design novel devices based on graphene.     

若干物理处理方法对稀土荧光粉Y2O3:Eu3+发光性能的影响

采用物理法对商品化稀土荧光粉Y2O3：Eu^3＋进行改性，考察了真空干燥温度、焙烧温度对其发光性能的影响。SEM和TEM观测结果表明，经过200℃真空干燥后，随着焙烧温度的增加，荧光粉的分散性得到改善，且以纳米颗粒为主（5～85nm）。XRD测量结果表明，随着焙烧温度的增加，Y203：Eu^3＋的结晶度逐渐增加。发射光谱测试结果表明，真空干燥温度为200℃，焙烧温度为1200℃时得到的样品的发光性能较好。     

Fabrication of suspended graphene devices and their electronic properties

Suspended graphene devices are successfully fabricated by using a novel PMMA/MMA/PMMA tri-layer resist technique. The gap between graphene and dielectric substrate can be easily controlled by the thickness of the bottom PMMA layer, and no wet-etching with hazardous hydrofluoric acid is involved in our fabrication process. Electrical characterizations on suspended graphene devices are performed in vacuum when in-situ current annealing directly leads to a significant improvement on transport properties of graphene, i.e., the increase of carrier mobility with the reduction of width of Dirac peak. Our results make a new opportunity to study intrinsic properties of graphene.     

铝酸盐紫色长时发光材料的研制

采用高温固相法制备了紫色长时发光材料CaAl2O4∶Eu2 , Nd3 . 研究了原料配比、激活剂和助熔剂含量、烧结温度、保温时间、还原气氛等对材料长时发光性能的影响. 当原料中Ca和Al的摩尔比为1.0∶2.3, 激活剂Eu2 含量为0.005 mol/mol, 助熔剂含量为1.6% (质量分数), 烧结温度为1350 ℃, 保温时间为4 h, 在氢气气氛下还原时, 所制得的材料的长时发光性能最佳. 当在原料中掺杂了辅助激活剂Nd3 后, 发光材料的初始发光亮度和发光时间都有了明显的提高.