Molecular orientation induced by cooling stresses. Birefringence in polycarbonate: III. Constrained quench and injection molding

Residual stress and birefringence distributions are determined in polycarbonate samples obtained by quenching in a specially designed apparatus and by injection molding. The molecular orientation is distinguished from the thermally and pressure-induced residual stresses. The birefringence in the quenched samples is found to be positive and almost constant, independent of the quench temperature, but varying strongly with initial quench temperature between 150 and 180°C. The residual stress level, as determined by layer removal and sectioning, is very low. The birefringence distribution is mainly due to a tensile equibiaxial orientation induced by transient cooling stresses built up above T_g. The samples which are injection-molded with a high injection speed and without packing pressure display the same birefringence distribution as the quenched samples, apart from a local maximum beneath the surface due to the shear flow during filling. Apart from the flow during filling and packing, the frozen-in molecular orientation in injection-molded samples is also induced by transient thermal stresses present during vitrification. The birefringence from thermally induced orientation was found to be of comparable magnitude to that from flow-induced orientation. For a correct prediction of molecular orientation the thermal strains above T_g must therefore be included in simulation programs. Because of the low level of thermal stresses, the application of a packing pressure will lead to tensile stresses at the surface in general. © 1994 John Wiley & Sons, Inc.     

Facile assembly of Bodipy-based metal ion sensor using click chemistry

In this study, two novel 4,4′-difluoro-4-bora-3a,4a-diaza-s-indacenes (BODIPY)-based metal ion sensors were synthesised using ‘click’ chemistry. The coordination modes and binding constants of the complexes formed with a range of metal ions were calculated. Results indicate that both BODIPY molecules can potentially serve as fluorescent sensors for the studied metal cations. The results also show that the BODIPY-based sensors have more selectivity for Zn (II) ions in the presence of other metal ions.     

Al70Co15Tb5Ni10合金中准晶T相和相关相的形成

 对Al₇₀Co₁₅Tb₅Ni₁₀合金进行了静高压（4.40 GPa）熔态（1 450 ℃）淬火（冷却速率为10² ℃/s）研究。首次在该系统中观察到准晶T相和一个新的十次准晶相关相形成。使用透射电镜对准晶相和准晶相关相进行了结构分析，得到了准晶相关相的晶胞参数。使用已有的理论模型对该相关相的形成进行了讨论。     

氧对LaOX：Ce3+和MFX：Ce3+体系猝灭作用的光谱研究

本文首次报道了LaOX:Ce3+和MFX:Ce3+(X=Cl-,Br-;M=Ba2+,Sr2+系列的光声光谱特性,并通过与荧光光谱的对照研究,讨论了氧对Ce3+在MFX和MF2(M=Ba2+,Sr2+基质中发光的猝灭作用.发现样品的发光随灼烧时间的加长而减弱,光声信号却依次增强,表明空气中氧对Ce3+发光的猝灭表现在其无辐射跃迁几率增加.同时发现由于非氟卤素的引入,便得MFX:Ce3+比MF2:Ce3+的抗淬灭性增强.文中着重研究了Ce3+在MFX基质中的发光,结果表明,在无氧合成条件下,MFX:Ce3+中Ce3+以发光中心Ⅱ(420nm附近)为主.     

热处理对聚芳醚腈的结晶行为及熔融的影响

利用广角X射线衍射 (WAXD)方法和示差扫描量热法 (DSC)研究了不同热处理温度 (Th)下聚芳醚腈(PCE)的微晶尺寸、结晶度及热性能的变化 .结果表明 ,淬火样品在熔融温度以下 ,热处理对微晶尺寸、结晶度、Tg 及Tm 均有不同程度的影响 ,且都随Th 的升高 ,其Dhkl、Xc 和Tm 也升高 .实验还发现 ,结晶样品的结晶度与原粉试样相比较均下降 ,说明PCE聚合物在熔融过程中出现了交联 ,导致了结晶度的下降     

Density-Density Propagator of the Luttinger Model of Spin-Half Fermions after an Interaction Quench

Motivated by recent research achievement of quantum interacting systems in non-equilibrium, we consider a Luttinger model with a suddenly switched-on interaction proposed by Cazalilla [M.A. Cazalilla, Phys. Rev. Lett. 97 (2006) 156403]. In order to compare with real systems, we extend Cazalilla's scenario to the spinful system. To find the influence of initial states on the time evolution of some non-equilibrium systems, we mainly focus on the density-density propagator. By comparison and analysis, we discover the different behavior of this non-equilibrium system. Further, it is found that the propagator saves strong memory of initial state, and the effects of right-left interaction cancel out in total density-density propagator.     

串联超导单元失超特性改善方法的仿真研究(英文)

为承受高电压与高电流等级,电阻型超导限流器的各个无感超导单元间不可避免地要进行串并联,由此会带来单元间失超不同步的问题.本文以单根344S超导带材在100ms的故障时间内,带材温度由92K升至300K时,失超电阻随温度的变化为基础,对两者间的关系进行了拟合.之后,以拟合函数为核心,利用Simulink的库中元件构建了单位长度344S带材的失超电阻模型并将其封装为模块.最后,搭建仿真电路模拟了故障时间内两个串联失超模块不同步失超的过程,仿真了分流电阻对失超不同步的改善并对分流电阻的选取进行了优化分析.结论证实,较小阻值的分流电阻更有利于改善失超特性.     

Ca、Ce掺杂对Y1Ba2Cu3O7-δ的超导电性及其晶格结构的影响

本文采用柠檬酸热分解法成功制备出了Y1-xCax(Ba1-xCex)2Cu3O7-δ(x=0、0.03、0.05、0.07、0.09)的一系列样品.我们采用标准的四端引线法对系列样品的超导电性进行了测量,测量结果表明:随着掺杂量x的不断增加,Y123的起始转变温度Tonset和临界转变温度Tc都在逐渐降低.利用X射线衍射仪对系列样品的晶格结构进行了表征分析,测量结果充分验证了上述结论,同时我们也简单阐述了Y123的晶格结构是如何影响其超导电性的.     

Density-Density Propagator of the Luttinger Model of Spin-Half Fermions after an Interaction Quench

Motivated by recent research achievement of quantum interacting systems in non-equilibrium, we consider a Luttinger model with a suddenly switched-on interaction proposed by Cazalilla [M.A. Cazalilla, Phys. Rev. Lett. 97 (2006) 156403]. In order to compare with real systems, we extend Cazalilla's scenario to the spinful system. To find the influence of initial states on the time evolution of some non-equilibrium systems, we mainly focus on the density-density propagator. By comparison and analysis, we discover the different behavior of this non-equilibrium system. Further, it is found that the propagator saves strong memory of initial state, and the effects of right-left interaction cancel out in total density-density propagator.     

填充液压力对聚醚砜中空纤维膜微结构和性能的影响

研究了聚醚砜／二甲基亚砜(PEs／DMS0)体系中填充液压力的变化对PES中空纤维结构及性能的影响。结果表明,随着填充液压力的增大,中空纤维膜的水通量增大,轴向取向度下降。为纺制具有合适性能的中空纤维膜提供参考。