Cyclopolymerization

The background and summary of the events that led to the discovery and confirmation of an unusual and unexpected mode of polymerization of certain vinyl monomers is presented. Originally, the process was described as an alternating intra‐intermolecular chain propagation mechanism. For convenience and because cyclic structures are introduced into the polymer chain, the term cyclopolymerization has been adopted. Early attempts to determine the relationship of cyclopolymerization to stereochemical control and to ladder polymer formation are reviewed. Also, it is pointed out that within 10 years of the introduction of the cyclopolymerization concept, worldwide commercialization of certain cyclopolymers and cyclocopolymers had begun. The extent of the research activity in this area of chemistry and its relationship to commercialization are emphasized. Two areas of research activity that are featured are chirality induction into well‐known polymers and synthesis of conjugated polymers via cyclopolymerization. Both areas are discussed, and suitable examples are included. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 3451–3461, 2000     

Effect of phosphonate additive on crystallization of gypsum in phosphoric and sulfuric acid medium

Understanding the mechanisms of growth and inhibition during crystallization of calcium sulfate is of primary importance for many industrial applications. For instance, inhibition of the crystallization process may be required to prevent scale formation in pipes, boilers, heat exchangers, reactors, reverse osmosis membrane surfaces, cooling water systems, secondary oil recovery utilizing water flooding techniques and desalination evaporators, etc. On the other hand, control growth and morphology of gypsum crystals is desired in achieving higher filtration rate and higher productivity of phosphoric acid from phosphate rocks. In this regard, this basic study is carried out to understand effect of Aminotris (methylenephosphonic acid (ATMP) on calcium sulfate dihydrate (gypsum) crystallization. The time elapsed between the achievement of supersaturation and the appearance of a solid phase (termed as induction time) is measured under different supersaturation ratios ranging from 1.018 to 1.979. The data are used to calculate the surface energy, critical nucleus size, and crystal growth rates of gypsum under different conditions. The results show that, the induction time decreases exponentially with increasing the supersaturation ratio. In addition, the surface energy decreases with ATMP compared to the baseline (without ATMP). Interestingly, with addition of the ATMP, the crystals mean and median diameters are found to decrease. The inhibition efficiency ranges from 16% to 59% depending on supersaturation ratio.     

三维感应成像测井仪设计与实现*

砂泥岩薄互层电阻率准确测量是提高泥质砂岩储层计算的一项重要工作。为了解决薄互层电阻率准确测量问题,该文提出一种三维感应成像测井仪的设计与实现方法。首先,基于感应电磁测量方法,设计由1个三轴发射器、4个单轴接收阵列和3个三轴的接收阵列组成的三维探测器。在此基础上,通过三维线圈系参数与结构创新设计、多频循环发射、高精度多道同步采集、高性能发射接收一体化集成等技术实现,在每一个深度点可获取78个电导率测量值。最后,利用数据校正与处理技术来消除各种环境影响,经过理论模型和实际资料的处理结果均证实,该仪器处理得到5条不同径向探测深度的水平电阻率与垂向电阻率、地层倾角等曲线,实现了对薄互层电阻率的准确测量。     

关于静电屏蔽上限的讨论

将导体壳放入外电场中,导体会在表面产生感应电荷,并达到静电平衡状态,导体壳腔内的电场处处为零,这就是静电屏蔽效应.然而,如果外电场极强,或者导体内部的自由电荷太少,以至于感应电场不能完全抵消外电场,则静电屏蔽效应将失效,这就是静电屏蔽的上限问题.本文从静电屏蔽的原理出发,将导体壳简化为一对平行金属平板的模型,定量的讨论了这一问题.通过计算我们发现,由于金属内存在大量的自由电子,在非极端问题中,宏观的导体装置都远远不会遇到静电屏蔽的上限问题.     

光学渡越辐射理论及其在直线感应加速器脉冲电子束诊断中的应用

匀速运动的带电粒子在穿过具有不同介电常数的两种媒质界面时要产生所谓光学渡越辐射。该辐射在粒子的入射平面上呈偏振行为;从辐射强度的角分布可以确定入射粒子的能量。在入射到双膜系统的情况下,由于干涉的发生,在第二膜前表面的强度角分布有振荡行为。利用这些现象,可对脉冲电子束包络半径、束电流密度的横向分布,束能量以及横向散角进行测量,依照这一原理在各LIA加速器上进行的脉冲电子束参数测量,获得的有效数据极大地提高了加速器的调试效率。     

弹头激波诱导燃烧特性的数值模拟

为了研究弹头激波诱导燃烧,基于有限体积的考虑化学反应的Navier-Stokes（N-S）方程,对预混氢气-空气化学恰当比时的燃烧流场进行了数值模拟.时间项基于2阶隐式LU-SGS格式,对流项基于Steger-Warming进行离散,化学反应源项采用对角化隐式处理.首先,研究了网格对燃烧爆轰流场结构的影响,并利用Lehr实验结果验证了计算方法的可靠性;其次,研究了弹头的飞行Mach数（Ma=4.18,5.11,6.46）、弹头直径（D=5,10,15 mm）对燃烧流场稳定性的影响.研究表明:计算网格对氢气-空气爆轰流场结构影响很大;弹头直径一定时,氢气-空气燃烧流场稳定性随着飞行Mach数的增大而增强;弹头飞行Mach数一定时,氢气-空气燃烧流场稳定性随着弹头直径减小而增强.