Co改性Mo/MCM-22催化剂上甲烷无氧芳构化及积炭研究

 研究了Co的添加对Mo／MCM－22催化剂甲烷无氧芳构化反应性能的影响．发现用共浸渍法制备的Co／Mo摩尔比为0．2的催化剂具有较高的活性,而先浸渍Mo后浸渍Co的催化剂具有较好的稳定性．XRD实验表明,Co及Mo的氧化物均高度分散在分子筛表面,其担载降低了分子筛的衍射强度．不同接触时间下催化剂的反应结果表明,接触时间长,积炭选择性随接触时间增加而迅速增加;接触时间短,积炭选择性随接触时间增加而减少．积炭催化剂的TG研究表明,催化剂上的积炭主要有两种形式．低温积炭随反应时间增加而迅速增多,高温积炭的变化则较为缓慢．低温积炭可能是导致催化剂活化和失活的主要原因．高温积炭可能是一种大分子量的碳氢物种,位于MCM－22分子筛的“超笼”中,表明MCM－22有较大的容积炭能力．     

消元法与带积分号的恒等式（英）

In this paper, our discussion is based on Zeilberg's basic idca[1] and use an elimination in the non-commutative Weyl algebra to get the differential operator. Thereby we can obtain the algorithm of proving identities of the form (∫∞-∞ )F(x, y)dy= a(x).     

荧光光度法测定饮料中的铅

对荧光光度法测定饮料中的铅进行实验研究,在3.0mol/L盐酸介质中,Pb2 与Cl-形成PbCl2-4配合物,此配合物在紫外光照射时发出蓝色荧光,应用荧光光度计检测出铅的含量.采用HNO3-HClO4混合酸体系(体积比为8:1)消化饮料样品.试验了盐酸用量、显色时间、干扰离子对铅测定的影响.该方法的检出限为9.0×10-3μg/mL,线性范围为0.3～9.0μg/mL,回收率为97.3%～100.2%.     

三烷氧基(β-酯基)乙基锗的合成及性质

生物及临床实验结果表明β-羧基乙基锗倍半氧化物[简式为(GeCH_2CH_2COOH)_2O_3]工具有抗癌等广泛的生物活性,且毒性极低。最近,我们又发现该化合物是一种具有双重性能的放射增敏剂,并合成了末见报道的类似物β-(N-芳基酰胺基)乙基锗倍半氧化物[简式(GeCH_2CH_2CONHAr)_2O_3],研究了其抗癌活性。本文所要报道的新有机锗化合物包括7个三烷氧基(β-酯基)乙基锗化合物[简式(R~2O)_3GeCH_2CHR~1COOR~2]和6个β-三氯锗基丙酸酯类化合物[简式Cl_3GeCH_2CHR~1COOR~2]。     

DBF-偶氮氯膦分光光度法富集测定水中痕量铋

铋是环境中的稀有分散元素，在地壳中的丰度约为0．2mg／L，海水和天然水中也有铋存在。铋对人体是有毒元素，主要积累在哺乳动物的肾脏，造成病变。白鼠试验表明，1．5mg／d有中毒症状，160mg／d中毒致死，用含铋27mg／L的废水浇灌农作物，会使农作物中毒枯死，因此有必要探索水样中铋含量的测定方法。水样中铋含量测定可采用三波长吸光光度法，但该方法对仪器精度要求较高。近几年，一些新的不对称变色酸双偶氮衍生物试剂成为光度法测定铋的重要显色剂，该类方法具有分析速度快、灵敏度和选择性较高的特点。笔者利用DBF-偶氮氯膦分光光度法测定水样中的铋含量，该法未见文献报道。     

Structural and electrical properties of Nd ion modified lead zirconate titanate nanopowders and ceramics

A modified sol-gel method is used for synthesizing Nd ion doped lead zirconate titanate nanopowders Pb_{1 - 3x}/2Nd_xZr₀.52Ti₀.48O₃ (PNZT) in an ethylene glycol system with zirconium nitrate as zirconium source. The results show that it is critical to add lead acetate after the reaction of zirconium nitrate with tetrabutyl titanate in the ethylene glycol system for preparing PNZT with an exact fraction of titanium content. It has been observed that the dopant of excess Nd ions can effectively improve the sintered densification and activity of the PNZT ceramics. Piezoelectric, dielectric and ferroelectric properties of the PNZT ceramics are remarkably enhanced as compared with those of monolithic lead zirconate titanate (PZT). Especially, the supreme values of piezoelectric constant (d₃₃) and dielectric constant (\it ε) for the PNZT are both about two times that of the monolithic PZT and moreover, the remnant polarization (P_r) also increases by 30%. According to the analysis of the structures and properties, we attribute the improvement in electrical properties to the lead vacancies caused by the doping of Nd ions.     

Experimental demonstration of single-mode fiber coupling using adaptive fiber coupler

Coupling plane wave into a single-mode fiber(SMF) with high and steady coupling efficiency is crucial for fiberbased free-space laser systems, where random angular jitters are the main influencing factors of fiber coupling. In this paper, we verified a new adaptive-optic device named adaptive fiber coupler(AFC) which could compensate angular jitters and improve the SMF coupling efficiency in some degree. Experiments of SMF coupling under the angular jitter situation using AFC have been achieved. Stochastic parallel gradient descent(SPGD) algorithm is employed as the control strategy, of which the iteration rate is 625 Hz. In closed loop, the coupling efficiency keeps above 65% when angular errors are below 80 μrad. The compensation bandwidth is 35 Hz at sine-jitter of 15 μrad amplitude with average coupling efficiency of above 60%. Also, experiments with simulated turbulence have been studied. The average coupling efficiency increases from 31.97% in open loop to 61.33% in closed loop, and mean square error(MSE) of coupling efficiency drops from 7.43% to 1.75%.     

退火温度对高分子薄膜中掺杂小分子的结晶和光谱学响应特性的影响

研究了小分子材料苝(EPPTC)在高分子材料聚芴衍生物(F8BT)薄膜中的结晶特性随温度的变化规律,以及由此引起的两种材料构成的异质结中激发复合体荧光发射特性的变化。实验结果表明,退火温度的升高会加强小分子与高分子材料在固体薄膜中的相分离。而小分子相在析出过程中,会在分子间作用力诱导下发生π—π团聚而结晶。晶体的尺度在达到小分子材料相变温度之前基本上随温度升高而增大。这一过程将破坏异质结结构,减小小分子与高分子间的接触面积,从而降低激发复合体的形成及其荧光发射强度。同时,由高分子向小分子发生的能量转移过程被显著减弱,而小分子晶相的荧光发射成分提高。这对于调控有机半导体异质结结构,进而改善光伏器件性能具有重要意义。     

近三年天津市中考化学试卷的研究报告

通过对近三年天津市中考化学试卷的教师问卷调查、学生作答实测及学生学习能力的跟踪调查与分析,提出新课程中考试题的特点为：(1)立足基础强调应用;(2)试题的选材关注社会与自然,提升试题的教育价值;(3)加强对化学实验的过程和方法及相关能力的考查;(4)试题情境趋向人文性,体现真实性。