Hydrothermal Synthesis of Acicular Lead Titanate Fine Powders

A pure, acicular lead titanate (PbTiO₃) fine powder with a white color has been prepared by hydrothermal synthesis. It is a new phase of PbTiO₃ with I 4 symmetry, cell parameters of a = 12.358 Å and b = 14.541 Å, and a density of 6.80 g.cm⁻³. The influences of pH (12.5 to 14.4), Pb/Ti ratio (1.0 to 1.6) in the feedstock, reaction temperature (130° to 230°C), time (0.25 to 4 h), starting materials, and additives on the formation of acicular PbTiO₃ under hydrothermal conditions have been investigated. The acicular PbTiO₃ with I 4 symmetry, referred to as the PX phase, can be converted to the perovskite-type (PE phase) of PbTiO₃ at about 605°C while its acicular morphology is essentially unchanged. The preferable conditions for preparing pure acicular PX-phase PbTiO₃ are that the pH is 13.0 to 14.0, Pb/Ti ratio is >1.3, reaction temperature is 170° to 200°C, time is 0.5 to 1.0 h, titanium butoxide (Ti[O(CH₂)₃CH₃]₄) is the starting material, and poly(vinyl alcohol) is an additive. The acicular grain of the PX phase is usually less than 100 nm in diameter and more than 1000 nm in length.     

叠后地震剖面的线性化波阻抗反演

本文提出了由井旁道出发逐道进行的叠后地震剖面的线性化波阻抗反演方法。每一道反演采用逐次线性化对波阻抗进行修正，反演的纵向分辨率为一个采样时间间隔，并以合成记录道与实际地震道的相似系数作为迭代收敛准则，已处理的地震道波阻抗作为下一道反演初始值。实际资料处理表明，该方法具有较高的分辨率和运算速度快的优点。     

前馈和反馈相结合的控制策略在宝钢线材厂控冷轧线上的应用实践

在详细分析料坯在水箱内冷却热过程特点的基础上，提出了前馈和反馈相结合的水流量优化控制策略，并将该策略应用于宝钢线材厂控冷轧线上。实际运行结果表明：该策略能够合理地控制水箱水流量，从而保证了线材水箱出口处的温度满足工艺要求，大大提高了线材成品的质量。所做工作对国内同类企业有重要的意义。     

Temperature Dependence of Ultra-Low-Frequency Dielectric Relaxation of Barium Titanate Ceramic

Based on a linear voltage ramp method, ultraslow dielectric relaxation of undoped BaTiO₃ ceramic has been carefully measured over the temperature range between − 180° and +120°C. Temperature dependence of the dielectric constant in the frequency range from 10 ⁻⁵ to 10⁻¹ Hz can be obtained using Kramers–Kronig equations. Close to the Curie temperature, the dielectric constant increases so rapidly that the Curie peak is overwhelmed. Two kinds of relaxation processes were observed in this experiment. Ferroelectric domain and mobile charge are proposed to be responsible for the relaxation over the temperature range. With temperature increasing, Maxwell–Wagner relaxation associated with mobile charge gradually dominates. From relaxation time constants at various temperatures, relaxation activation energies about 0.06 and 0.09 eV are identified.     

丁苯胶乳改性道路沥青的推广应用

用丁苯胶乳对胜利１００号沥青进行改性试验．发现随着胶乳掺量的增加．沥青的高温性能、粘结性能改善幅度也大。但综合考虑沥青生产成本等因素．认为：对丁苯胶乳改性胜利１００号道路沥青．掺胶量控制在２％即可满足一般高等级道路工程的需要。文中还介绍了丁苯胶乳沥青近年来的推广使用情况并做了相应的技术经济分析和建议。     

溶胶-凝胶法制备TEOS-DOS基SiO2疏水减反射膜:溶胶微结构对膜性能的影响

以乙醇为溶剂,正硅酸乙酯(TEOS,tetraethoxysilane)在氢氧化铵催化下水解缩聚为纳米尺度的无定型SiO2溶胶颗粒,二甲基二乙氧基硅烷(DDS,dimethyldiethoxysilane)在盐酸催化下水解缩聚为线状聚二甲基硅氧链.用混合溶胶在玻璃基片上旋转镀膜,然后于80℃空气气氛下热处理.实验证明通过DDS将疏水的双甲基链引入镀膜胶体,使膜兼具疏水性和减反射性能.利用激光散射粒度分析仪和电子显微镜研究了溶胶颗粒的粒度变化和聚集情况等溶胶微结构,用物理吸附仪研究了膜的孔结构,考察了热处理前后膜的疏水性和透射谱,得到了溶胶微结构与膜性能之间的关联.     

液压同步剪系统的设计

本文通过对蜂窝陶瓷载体成型过程的分析，指出在其成型过程中存在的问题，提出了采用液压同步剪解决这些问题的方法。论文分析了同步剪的工作原理，给出了其液压原理图及其设计特点。     

DNA/lipid complex organogel with shape‐memory behavior

DNA and amphiphilic N,N,N‐trimethyl‐N‐hexadecylammonium bromide (THAB) were stoichiometrically mixed together to produce a DNA–lipid complex, which was dissolved in dimethyl sulfoxide (DMSO) at 65°C and then crosslinked with isophorone diisocyanate (IPDI). The obtained organogel swelled reversibly in DMSO, responding to the variation of temperature. Interestingly, we observed that the gel exhibited a temperature‐dependent shape‐memory behavior. Above 65°C, whatever the shape the gel was deformed to, it could retain the new shape as the temperature was decreased to room temperature, while, when the gel was heated to 65°C again, it could recover its initial shape. The shape‐memory characteristic is supposedly originated from the transition between the close‐packed and the destroyed DNA/lipid conformation. The elastic urethane crosslinking bonds between base‐pair sites act as a fixing phase. The gel holds promise in its application as a gentle actuator. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 259–263, 2002     

交点计算的几种方法

在工程测量中，经常涉及到交点计算，如何运用现有的工具快速地计算出交点非常重要。本文介绍了利用控制器、AutoCAD绘图软件和Excel计算交点的方法，供大家参考。