Effect of site-selective substitution in bulk superconducting Tl2Ba2CaCu2O8

Magnetization measurements were carried out on bulk Tl₂Ba₂CaCu₂O₈ (referred to as Tl-2212) and on various site-selective substituted Tl-2212 samples. At 5K between 0 and 4.5 T, the 5 at. % Mg-doped Tl-2212 (Tl,Mg-2212) samples displayed enhanced pinning as demonstrated by a field dependent increase of the magnetic critical-current density J_c by 18 to 25 percent over that of pristine Tl-2212. Excess Mg (10–15 at. %), however, is deleterious. Rietveld refinement of the x-ray diffraction pattern showed Mg on the Tl sites. Auger electron spectroscopy analysis showed part of the Mg on grain boundaries. The flux-creep activation energies are higher for flux expulsion than for flux penetration in both Tl-2212 and Tl,Mg-2212 samples; the latter displays higher individual values. Our results demonstrate an increase in the number density of flux lines as a result of increased density of atomic-size-structural, defects by Mg (5 at. %) doping. In the Tl_2−yBa₂(Ca_1−zY_z)Cu₂O_8−x(z=0–0.3; single phase; x and y represent oxygen and thallium vacancies) system also studied, the T_c decreases as z increases. At z=0.3, the sample becomes an antiferromagnetic semiconductor.     

强化管理提高特超稠油开发效果

河南稠油资源品位低,开采难度大,效益差。近几年,通过实践,逐渐摸索出一套适应开发需要的科学生产管理方法,明显地改善了稠油开发效果。以提高热效率为核心,形成了八大生产管理制度;深化油藏认识,使油藏-工艺-管理三者有机结合,充分利用了地层储热,提高了周期吞吐开发水平;以降粘、防砂、堵窜为重点,实现了地面-井筒-油层三位一体工艺配套,保证了油井正常生产。     

Synthesis of NaYF4:20% Yb3+,2% Er3+,2% Ce3+@NaYF4 nanorods and their size dependent uptake efficiency under flow condition

Lanthanide doped fluorescent nanoparticles have gained considerable attention in biomedical applications. However, the low uptake efficiency of nanoparticles by cells has limited their applications. In this work, we demonstrate how the uptake efficiency is affected by the size of nanoparticles under flow conditions. Using the same size NaYF₄:20% Yb³⁺,2% Er³⁺,2% Ce³⁺ (the contents of rare earths elements are in molar fraction) nanoparticles as core, NaYF₄:20% Yb³⁺,2% Er³⁺,2% Ce³⁺@NaYF₄ core–shell structured nanorods (NRs) with different sizes of 60–224 nm were synthesized by thermal decomposition and hot injection method. Under excitation at 980 nm, a strong upconversion green emission (541 nm, ²H_11/2 → ⁴I_15/2 of Er³⁺) is observed for all samples. The emission intensity for each size nanorod was calibrated and is found to depend on the width of NRs. Under flow conditions, the nanorods with 96 nm show a maximum uptake efficiency by endothelial cells. This work demonstrates the importance of optimizing the size for improving the uptake efficiency of lanthanide-doped nanoparticles.     

Ce^3＋,Sb^3＋共激活的亚超细磷光体的微波快速合成和发光特性

首次采用微波辐射法快速合成了亚超细CaS:C^3 ,Sb^3 高效绿光磷光体，发现Ce^3 与Sb^3 离子之间存在着能量传,租是属于多极子相互作用的共振传递，因而Ce^3 对CaS:Sb^3 的发光有明显的敏化和增强。微波场作用下合成的双掺磷光体的激发峰与发射峰值分别恒定在259nm 和523nm处，并没有像传统高温固相合成法那样，随掺杂离子浓度的增大而发生红移现象。SEM照片显示，采用含不同一价阳离子（Na^ ,K^ ,NH4^ )无机盐作助熔剂制得的亚超细CaS:Ce^3 ,Sb^3 磷光体平均粒径为300nm-500nm，但其晶体形貌分别为立方形、球形和团聚状的雪花形，其中球形磷光体荧光最强。     

Novel blue‐light‐emitting polymers based on a diphenylanthracene moiety

New luminescent copolyethers with diphenylanthracene‐emitting segments and electron‐transporting benzoxazole phenyl were successfully synthesized by aromatic nucleophilic substitution. The polymers, characterized by NMR and IR spectroscopy, were obtained in high yields, showed good solubility in various organic solvents, and had high thermal stability with high glass‐transition temperatures (125–129). The number‐average molecular weights of the polymers were 10,000–20,000, and they had polydispersity indices of 1.2–1.4. The optical and electrochemical properties of the polymers were also investigated. The pure blue emission for the polymers (maximum wavelength = 430–440 nm) was obtained with high photoluminescence quantum efficiency (76–78%) in a chloroform solution. The blue electroluminescence for the poly(TDPB) (maximum wavelength = 440 nm) was obtained with a turn‐on voltage of 15–20 V when simple light‐emitting diodes (indium tin oxide/polymer/Al) were fabricated. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2151–2157, 2006     

Investigations of surface degradation of high‐density polyethylene materials resulting from tracking,using physicochemical analysis

In the present work tracking phenomena were studied with high‐density polyethylene (HDPE) materials under dc voltage, with NH₄Cl and acid rain as contaminants. It was determined that the tracking time of the material depends on the conductivity and flow rate of the contaminant. Furthermore, physicochemical analysis by wide‐angle X‐ray diffraction studies, differential scanning calorimetry, and luminescence spectroscopy was carried out, whereupon it was concluded that the tracking process is a surface‐degradation process. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 2843–2849, 2002; DOI 10.1002/app.10260     

Mn^2＋在铝酸盐中的发光

用金属硝酸盐、稀土氧化物和乙酸锰为原料，用燃烧法合成了Ce^3 、Tb^3 、Mn^2 共激活的铝酸盐绿色荧光粉，在Ce^3 和Tb^3 共激活的铝酸盐体系中掺入Mn^2 后，发射峰中出现锰的特征峰。通过对其结构的分析，对Mn^2 发光和最佳掺杂量给出了合理的解释．同时研究了不同碱金属和碱土金属离子代替Mg^2 时，对Mn^2 发光的影响．     

紫外线对BaFCl：Eu光激励发光的增强效应

对X射线辐照后的BaFCl:Eu样品，通过研究紫外线辐照对光激励发光的影响，发现在一定条件下紫外线对光激励发光有增强的作用，并且根据光谱研究提出了光激励发光的过程为Eu^2 和陷阱争夺激发态电子的观点，从机理上对这一现象进行了解释。     

长链羧酸铕四元配合物的合成及其发光性质

合成了铕与长链羧酸、二苯甲酰甲烷、邻菲啰啉形成的四元配合物,用元素分析、红外光谱、核磁共振氢谱和紫外光谱对所合成的铕四元配合物进行了表征。由于长链羧酸的引入,铕配合物在氯仿等挥发性有机溶剂中具有良好的溶解性,这为今后与高分子基体复合创造了条件。铕配合物在342nm光波激发下,发出以铕的特征发射谱线612nm左右为主的强荧光。     

矩形纵向涡发生器平板强化换热的实验研究

利用热质比拟萘升华技术,在吸入式风洞中对矩形纵向涡发生器平板强化换热进行了实验研究。在雷诺数范围2.3×105~5.4×105内,通过改变涡发生器迎流冲击角β,得到强化换热的效果,并对参数进行优化。