聚丙烯孔洞铁电驻极体膜的电极化及其电荷动态特性

根据栅控恒压电晕充电组合反极性电晕补偿充电法的实验结果计算出铁电驻极体的极化强度.结果说明，伴随着薄膜内孔洞气体的Paschen击穿，该铁电体的极化强度随栅压增加而显著上升.利用上述充电方法和热刺激放电(TSD)谱的分析讨论了这类空间电荷型宏观电偶极子，及与其补偿的空间电荷热退极化的电荷动态特性；阐明了这两类俘获电荷的能阱分布，即构成宏观电偶极子的位于孔洞上下介质层内的等值异号空间电荷分别被俘获在深、浅两种能值陷阱内，而位于薄膜表面层的注入空间电荷则被俘获在中等能值陷阱中. 关键词： 反极性电晕补偿充电法 铁电驻极体 充电电流 热刺激放电     

Removal,recovery and enrichment of metals from aqueous solutions using carbon nanotubes

Environmental pollution caused by toxic metals (heavy metals, radioactive metals, etc.) is one of the major global issues, thus removal of toxic metals from contaminated water seems to be particularly important. On the other hand, the recovery and enrichment of metals, especially noble metals, from waste water is also crucial. To address these issues, nanotechnology plays an essential role in environmental monitoring and pollution control. To remove metals from contaminated water, or enrich metals from waste water, carbon nanotubes (CNTs) and their composites have attracted great attention due to their excellent adsorption performance. The removal efficiency for metal ions by CNTs was observed aroud 10–80 %, which could be improved to approach 100 % by selectively functionalizing CNTs with organic ligands. Herein, we review the applications of CNTs in treatment of toxic metal-containing wastewater for environmental monitoring and metals recovery. Due to their higher sensitivity and selectivity towards the enrichment of metals or detection of toxic metal pollution of the environment, and the latest research progress of using CNT composites for metal treatment is also discussed.     

稳态和动态荧光研究疏水缔合共聚物P(AM/POEA)的自缔合行为和聚集体

应用稳态和动态荧光光谱方法,包括荧光探针、标记荧光和荧光淬灭等研究了共聚物P(AM/POEA)在水溶液中的自缔合性质.这种共聚物由丙烯酰胺(AM)和少量疏水单体2-苯氧乙基丙烯酸酯(POEA)组成.实验结果表明这类共聚物的自缔合行为和聚集体结构主要取决于聚合物的链结构和浓度.由胶束共聚合方法得到具有多嵌段结构的共聚物,它们容易发生疏水缔合,并产生很强的增粘作用,而由普通共聚合方法得到的无规共聚物却没有这些性质.同时这类聚合物的缔合类型及其增粘能力也直接与共聚物中的疏水体含量相关,随疏水体含量增加,由于分子间和分子内缔合的竞争,出现粘度先增后降的现象.在荧光研究的基础上提出了多分子聚合物聚集体的结构模型,它随聚集体浓度增加,进一步形成多联聚集体和网状结构.同时还观察到聚集体中疏水体有序排列现象.     

恒流电晕充电对聚四氟乙烯多孔薄膜驻极体驻极态的影响

利用常温下恒流和恒压电晕充电、充电后的等温表面电位衰减、热刺激放电和扫描电镜等实 验手段研究了恒流和恒压电晕充电技术对聚四氟乙烯多孔薄膜驻极体驻极态的影响.与恒压电晕充电相比较，恒流电晕充电时由于流过薄膜的电流恒定，增加了注入电荷在多孔结构厚度方向界面处的俘获概率，使沉积电荷密度上升，改善了驻极体的储电能力.然而，这些位于不同层深多孔界面处的俘获电荷在这类功能膜储存或使用过程中，经外激发从脱阱位置 以跳动（hopping）模式输运至背电极的路径相对缩短将导致脱阱电荷衰减较快. 关键词： 恒流电晕充电 聚四氟乙烯多孔膜 驻极体 电荷稳定性     

Nonparametric Quantile Inference for Cause-specific Residual Life Function Under Length-biased Sampling

Acta Mathematicae Applicatae Sinica, English Series - This paper considers a competing risks model for right-censored and length-biased survival data from prevalent sampling. We propose a...     

一种新型香豆素酮可见光敏化染料的合成及其光引发性质的研究

高效的可见光光敏引发体系是目前光聚合研究中的重要领域.3,3′-二(7-二乙胺基)香豆素酮(R)已被公认为一种高效的可见光聚合敏化染料,并可以与Ar⁺激光488 nm波长匹配.本文新合成了一种染料3-(4-二乙胺基-苯丙烯酰基)-7-二乙胺基香豆素(S).实验发现在普通碘钨灯照射下,S/邻氯六芳基双咪唑(HABI)体系具有比已有高效染料R/HABI体系更快的光漂白速度和更高的引发聚合效率,是一种新型高效的可见光光敏聚合引发体系.而且S在不同溶剂中的最大吸收波长在452～489 nm之间,比R红移16～30 nm,因此该体系可以更好地与Ar⁺ (488 nm)激光器匹配.本文对该染料的光敏化机理进行了探讨.     

Lagrange multiplier method used in BESⅢ

In this paper, the kinematic fitting with the Lagrange multiplier method has been studied for BESⅢ experiment. First we introduce the Lagrange multiplier method and implement kinematic constraints. Then we present the performance of the kinematic fitting algorithm. With the kinematic fitting, we can improve the resolution of track parameters and reduce the background.     

Syntheses of Novel Asymmetric Cyclopentanone Dyes and Measurement of Two－photon Absorption Cross－section

A simple synthesis route with a high yield of novel asymmetric cyclopentanone dyes 3a—3e and their highly two-photon up-converted fluorescences are reported. The dyes have good solubilities in most of ordi-nary solvents, a wide UV absorption wavelength range from 380—540 nm, and high fluorescence quantum yields. The two-photon absorption cross-sections of dyes 3a—M were measured in chloroform by a two-pho-ton induced fluorescence method. All of these properties of the new dyes make them suitable for being used as two-photon fluorescent probes.     

压力膨化后的热处理温度对PP蜂窝膜驻极体机电性质的影响

研究了经压力膨化后的热处理温度对聚丙烯蜂窝膜(cellular PP)驻极体机电性能的影响.结果表明，在从常温至PP熔融温区内，压力膨化工艺处理后PP蜂窝膜的厚度随着热处理温度的升高而逐渐增大；然而热处理温度对PP蜂窝膜的压电活性及其相关性质的影响具有显著不同的规律，在90℃时，PP蜂窝膜的弹性模量和机电耦合系数分别出现谷值和峰值，同时压电d₃₃系数达到377pC/N的最大值.随着热处理温度的升高，它们的谐振频率的变化范围约为794到371kHz. 关键词： 热处理温度 PP蜂窝膜 压电性 压力膨化工艺     

直流老化对CaCu3Ti4O12陶瓷介电性能的影响

在电场为3.5 kV/cm的条件下, 对CaCu₃Ti₄O₁₂陶瓷进行了60 h的直流老化, 研究了老化过程对CaCu₃Ti₄O₁₂陶瓷介电性能和电气特性的影响. J-E特性测试结果表明, 直流老化导致CaCu₃Ti₄O₁₂陶瓷击穿场强、非线性系数和势垒高度明显降低. 介电性能测试结果表明, 低频介电常数和介电损耗明显增大, 并且介电损耗随频率的变化遵从Debye弛豫理论, 可分解为直流电导损耗和弛豫损耗, 直流老化主要导致了电导损耗的增加. 在低温233 K, 介电损耗谱中出现两个弛豫峰, 其活化能分别为0.10, 0.50 eV, 认为对应着晶粒和畴界的弛豫过程, 且不随直流老化而变化. 通过电模量谱对CaCu₃Ti₄O₁₂陶瓷的弛豫过程进行了表征, 发现直流老化导致的界面空间电荷在外施交变电场的作用下符合Maxwell-Wagner极化效应, 并在低频区形成新的弛豫峰. 在高温323-473 K的阻抗谱中, 晶界弛豫峰在直流老化后明显向高频移动, 其对应的活化能从1.23 eV 下降到0.72 eV, 晶界阻抗值下降了约两个数量级. 最后, 建立了CaCu₃Ti₄O₁₂陶瓷的阻容电路模型, 分析了介电弛豫过程与电性能之间的关联.