Intrinsic Elastic, Dielectric, and Piezoelectric Losses in Lead Zirconate Titanate Ceramics Determined by an Immittance-Fitting Method

The material coefficients of "soft" and "hard" lead zirconate titanate (PZT) ceramics were determined as complex values by the nonlinear least-squares-fitting of immittance data measured for length-extensional bar resonators. The piezoelectric d -constant should be a complex value to obtain a best fitting between observed and calculated results. Because the elastic, dielectric, and piezoelectric losses determined in this process were not "intrinsic" losses, a calculation process to evaluate the "intrinsic" losses was proposed. It was confirmed that the intrinsic losses were smaller than the corresponding extrinsic losses. The intrinsic piezoelectric loss existed in both soft and hard PZTs; ∼50% of the loss of piezoelectric d -constant was derived from the elastic and dielectric losses. The most notable difference between the soft and hard PZTs was observed in their elastic losses.     

铅酸电池管式正极添加四碱式硫酸铅晶种的研究

在铅酸电池正极铅粉中加入一定量的四碱式硫酸铅（4BS）,按照工业化的操作工艺,制备出原料中4BS含量不同的正极板,并与常规负极板组装成小电池。对正极的初始容量和循环寿命等电化学性能做了测试,结果表明,在添加粒径为1.5 μm的4BS质量分数达1%时,65 ℃固化后,正极初始容量和循环寿命分别为未加4BS正极的1.02倍和1.06倍,4BS的加入提升了电池容量和电池寿命等的综合性能;XRD结果显示,原料中加4BS的正极中β-PbO₂含量稍高于未加4BS的正极;SEM结果显示,加4BS的正极活性物质更细小,大小更均匀。     

PAR分光光度法测定汽油中的痕量铅

研究了快速测定汽油中痕量铅的方法。测定经盐酸处理过的汽油与 PAR反应生成的络合物。该显色体系最大的优点是可在水相中直接用光度法测定样品中铅的含量。该配合物最大的吸收波长为 5 2 0 nm,ε52 0 =2 .2× 10 4 L· (m ol· cm ) - 1 ,Pb浓度在 0～ 2 5 .2μg· m L- 1 范围内线性关系良好 ,回归方程 A=0 .12 711C- 0 .0 6 2 93,相关系数为 0 .9992 ,检出限为 0 .4 1μg· m L- 1 。本方法显色迅速 ,稳定 ,操作简便 ,避免了使用氰化钾剧毒试剂 ,以及萃取等烦琐操作 ,可在 35 min内完成 1次测定     

利用蓄电池废硫酸和硼泥制备高品质氢氧化镁

利用废铅酸蓄电池中的废硫酸作为浸取剂,对硼泥中的镁进行回收并制备出高品质的氢氧化镁产品。实验得出了酸浸硼泥的最佳工艺条件：酸浸温度为80℃;酸浸时间为30 min;酸用量为硫酸与硼泥质量比为1.2∶1。利用不同金属水解pH的不同,将酸浸过程中从硼泥和废硫酸中引入的杂质依次去除,得到精制硫酸镁溶液。由精制硫酸镁制取氢氧化镁的工艺条件为：常温下,沉淀剂为氨水,反应终点pH为11,反应时间为2 h,反应物在50℃下陈化12 h,过滤、洗涤后105℃烘干。实验考察了不同沉淀剂对氢氧化镁形貌的影响。所得氢氧化镁纯度在97%以上,粒径在0.1～1μm之间,各项指标均优于中国化工行业标准。     

基于链接关系分析的PgaeRank改进算法研究

经典的PageRank算法对所有出链网页采用平均分配链出权值的策略,这种方式会导致网页PR值计算的不准确性。通过对链出网页的重要性进行分析,优化链出权值的分配策略,实验结果表明,改进的PageRank算法使得页面排序的结果更加优化。     

基于随机游走模型的维基百科语义关系研究

运用随机游走模型提出了一种基于维基百科的语义相关度的计算方法。维基百科中包含了丰富的链接结构,这些链接结构一定程度上能够反应词条之间概念上的相关性,以内容链接和外部链接关系来计算基于维基百科的语义相关度,并在WS-353数据集上进行了实验,取得了较好的准确性。     

Fabrication of High-Curie-Point Barium-Lead Titanate PTCR Ceramics

High-Curie-point semiconducting barium-lead titanate positive temperature coefficient of resistivity (PTCR) ceramics of composition Ba_0.897Pb_0.1La_0.003TiO₃ and Ba_0.5Pb_0.5La_0.003TiO₃ were prepared. The starting powders were synthesized by reacting commercial BaTiO₃, PbO, and TiO₂. To avoid the nonstoichiometry due to the volatilization of Pb during the sintering process, a lead atmosphere sintering approach with PbTiO₃ as packing powder was used. The samples being fabricated by this method show a PTCR effect of 3 to 4.5 orders of magnitude above the Curie point. The curie points were about 180°C for Ba_0.897Pb_0.1La_0.003TiO₃ and about 360°C for Ba_0.497Pb_0.5La_0.003TiO₃.     

选择性螯合滴定法测定电镀液中的锡铜铅

提出了测定电镀液中锡铜铅的一个简易快速螯合滴定法.用EDTA螯合锡(Ⅳ)、铜(Ⅱ)、铅(Ⅱ)和其它金属离子,然后分别用三羟基苯甲酸、巯基丁二酸和氨荒丙酸解蔽.释放出的EDTA,用锌标准溶液反滴定(XO-CPB为混合指示剂).终点变化相当敏锐.研究了测定锡、铜、铅时一般共存离子的干扰.此法已被成功地用于测定锡-铜-铅合金电镀液和镀层锡铜铅合金中的锡、铜和铅.     

一种新的MANET节点—链路稳定度模糊评估模型

利用模糊数学思想,针对MANET提出了一种稳定性评估模型,即节点—链路模糊稳定度模型。该模型通过对位置临界点和速度进行综合模糊建模,用模糊值精确衡量MANET中节点与链路的稳定性高低。理论和模拟分析证明了该模型能更有效地对MANET的稳定性和生存能力进行定量评估。在该模型下,MANET中节点与链路在大尺度时间区间内的稳定性要高于小尺度时间区间内的稳定性。     

Use of Re(C5H7O2) in preparation of catalysts for olefin metathesis

New catalysts for olefin metathesis are obtained upon interaction between rhenium trisacetylacetonate and -Al₂O₃ surface. After high temperature treatment in flows of O₂ and N₂ and addition of organometallic compound as a cocatalyst the activity of the resulting catalyst exceeds that of known Re/Al₂O₃ catalysts prepared by impregnation. The catalysts exhibit maximal activity at a cocatalyst surface concentration of 3 × 10^–7 mol/m². Further increase of the cocatalyst concentration leads to deactivation.