Secondary instabilities of linearly heated falling films

Secondary instabilities of linearly heated failing films are studied through three steps. Firstly, the analysis of the primary linear instability on Miladinova's long wave equation of the linearly heated film is performed. Secondly, the similar Landau equation is derived through weak nonlinear theory, and a two-dimensional nonlinear saturation solution of primary instability is obtained within the weak nonlinear domain. Thirdly, the secondary (three-dimensional) instability of the two-dimensional wave is studied by the Floquet theorem.Our secondary instability analysis shows that the Marangoni number has destabilization effect on the secondary instability.     

Synthesis of a new meso／microporous composite molecular sieve of MCM-41／mordenite

An MCM-41/mordenite composite with twofold porous structure and stepwise-distributed acidity was prepared for the first time by using zeolite mordenite as the silica-alumina source. The composite molecular sieve has been investigated and compared with a mechanical mixture of mordenite and MCM-41 for their structure, acidity and catalytic activity by means of XRD, N2 adsorption and desorption, HRTEM, DTG, NH3-TPD and catalytic reaction. The characterization results show that the structure and property of the composite molecular sieve are quite different from those of the mechanical mixture, which might be ascribed to the incorporation of secondary building units characteristic of zeolite mordenite into the mesoporous walls of the composite which gives rise to the thicker mesoporous walls, the higher hydrothermal stability and more strong acid sites. Furthermore, the new strategy could be used as a new general method for the preparation of catalysts for the reaction system with multifold large molecules, and the results were well confirmed by the dealkylation of C10^ aromatic hydrocarbon.     

基于改进PSO算法的连铸二冷过程优化仿真

连铸小方坯二冷过程优化是在实现二维传热建模和数值求解的基础完成的。冶金准则的多目标性,模型数值离散化大的计算量以及凝固相变存在引起模型求解的非线性,导致传统优化方法搜索效率低下。采用粒子群算法优化连铸二冷过程。为加强局部搜索能力,引入混沌序列对陷入局部极小点的惰性粒子重新初始化,在迭代中产生局部最优解的邻域点,帮助惰性粒子逃离束缚并且快速搜寻到最优解。仿真结果表明,改进的PSO算法有更好的搜索效率,取得了较好的效果。     

浅谈中专《秘书基础》教学改革

提出顺应文秘专业素质教育的要求及中职《秘书基础》课程的改革方针,并阐述了具体方法。     

AutoCAD中三维深沟球轴承的参数化设计

由于AutoCAD中没有专门绘制三维深沟球轴承命令,因此采用二次开发的方法可迅速绘制所需的三维轴承.该方法采用V isual LISP语言编制程序进行二次开发AutoCAD三维深沟球轴承绘制方法的功能,为AutoCAD新增绘制三维深沟球轴承功能的命令,使得在进行机械产品三维CAD时,绘制三维深沟球轴承更为方便,提高三维设计的绘图工作效率.     

用于控制透平叶栅内部流动的端部孔隙结构

为利用端部孔隙结构控制叶栅二次流损失,对一种端部孔隙结构在不同攻角下对透平静叶栅内部流场的影响进行数值模拟。结果表明:大负攻角下,该孔隙结构有效地控制了透平叶栅头部压力面的分离泡,减少了损失;在其他攻角下,该结构对该文考察的叶栅没有表现出明显的改善作用。结合该孔隙结构和另一种由原始叶型优化后的叶片进行联合造型,对其在不同攻角下的性能进行了考察。经联合造型后的叶栅与原始叶栅相比在各个攻角下的流动损失均有大幅度降低,大负攻角下效果尤为明显。     

新制二级学院学生特点及管理思路探索

新制二级学院的学生管理工作必须建立在对二级学院学生特点分析的基础上，有的放矢，才能确立正确的管理思路。     

深层砂岩次生孔隙的成因及其与异常超压泄漏的关系——以黄骅坳陷板桥凹陷板中地区滨油组为例

黄骅坳陷板桥凹陷老第三系埋藏深度超过 3 5 0 0 m的砂岩体普遍处于超压系统中 ,异常超压的形成与油气的初次运移直接相关 ,与断层相关的异常超压泄漏是形成次生孔隙的一个重要因素。次生孔隙是因颗粒或胶结物的溶解而形成的 ,异常超压并不是形成有效次生孔隙的直接原因 ;但由于超压在断层处的泄漏 ,导致砂岩体中的溶解物质得以搬运出储层 ,从而形成次生孔隙并伴随着孔隙度的净增加。板中地区深层异常超压的形成和泄漏是一个动态的平衡过程 ,次生孔隙形成后随着油气的介入而得以保存下来     

RH脱碳模型的建立和测试

笔者针对无排气信息的 RH精炼装置 ,在碳氧平衡原理的基础上 ,结合工艺人员提供的经验知识 ,经过大量数据统计和仿真测试建立了 RH脱碳模型 .此文着重对其基本原理、模型主要流程、建模仿真过程和仿真测试结果进行阐述 .实践证明该模型精度优于宝钢现用模型     

LF炉冶炼超低硫钢的工艺条件

提出了采用热力学计算分析确定LF炉冶炼超低硫钢工艺条件的方法·分析表明,可通过提高炉渣碱度、强化渣钢脱氧、控制渣钢原始硫质量分数和渣质量,来实现超低硫钢的冶炼·150tLF炉生产实践表明,在原始钢水硫平均为00146%条件下,通过控制规定的工艺条件,经LF处理后的钢水硫质量分数平均可达00044%·再经VD处理后,可实现成品硫质量分数为00027%的超低硫钢生产·在上述条件基础上,将原始硫质量分数控制在00058%以下或保证渣金硫的分配比在250以上或采用双渣操作,LF炉可精炼0002%以下极低硫钢