埋地曲管流固耦合振动分析的数学建模

输液管道(包括埋地管道)的振动问题是当前学术界的一个研究热点,而数学建模又是解决问题的关键。将土约束简化为均布非线性弹簧、线性弹簧和均布荷载,推导出了埋地管道的振动微分方程。     

水下油气管道随机振动的模拟算法

水下穿越输油气管道具有施工方便、投资省等优点.但水下穿越段一旦遭到破坏,其破坏点不易被发现,修复困难,因此水下管道的振动分析研究具有重要意义.文章从分析水下管道的受力情况出发,建立了描述水下管道振动的随机微分方程,求解出描述振动受力的随机过程,从而给出这种振动受力的计算和模拟方法.其结果可引申到在流体中运动的物体,如大气中的各种飞行器及其部件的振动模拟以及寿命预测等应用研究领域.     

工程管道与人体血管之比较分析

工程管道与人体血管都是典型的流固耦合系统,它们的性质有很多相似之处。文章分别对两者的基本情况、雷诺数、振动微分方程的形式及一些常见问题进行了比较分析,给出了工程管道与人体血管问题的预防措施。     

输液管道振动声辐射研究

针对输液管道振动大,噪声污染严重的问题,本文结合振动理论、声场理论、应用有限元以及边界元方法对输液管道受激振动的噪声辐射过程进行研究,并提出了一种新的低噪声管道结构设计方法。     

声音的产生与传播趣题赏析

题1:古时的士兵为了能及早听到敌人夜袭的马蹄声,常常睡在地上,并把耳朵贴在地面。以下解释错误的是( ) A.马蹄踏在地面上,使地面振动 B.马蹄声可以沿地面传播 C.马蹄声在空气中不能传播 D.声音在土地中传播比在空气中传播快     

附加程差的解析表示

本文以菲涅耳公式为基础 ,给出两束反射光振动面夹角的解析表达式 ,用解析的方式讨论了薄膜干涉的附加程差问题。讨论了各种情况的附加程差的问题 ,更正一些错误的说法     

大型核电机组给水管道振动初探

以某1000MW大型核电机组在调试试运期间给水管道振动为例,分析讨论了影响给水管道系统振动的主要因素,提出了应对措施。     

高中化学教学过程的深入反思

文章首先就当前存在于高中化学教育活动中的问题做出了必要的分析,指出教学目标的偏移和知识体系的碎片化已经成为当前阻碍学生系统学习的重要问题,而后进一步有针对性地给出相关建议,从构建完整知识体系和正视生源性错误两个方面,对提升当前高中化学教学质量给出了建议。     

工作参数对充液直管振动特性影响的试验研究

用试验方法研究了阀门的开启程度、支撑位置变化和管道内液体脉动对管道系统振动特性的影响．结果表明：由阀门开启程度引起的振动频率随着阀门开启程度的减小而增大;由可移动支撑位置改变引起的两个振动频率随着可移动支撑向中间的靠近而逐渐远离;由管道内液体脉动引起的振动频率随着可移动支撑向中间靠近和阀门开启程度的减小而减小．     

高一物理学前探营

一、不定项选择题(本题为不定项选择应，在每小月给出的4个选项中.有的只有一个选项正确.有的有事个选项正确.) 1.“坐地日行八万里，巡天遥看一千河”这一句诗表明了(). A坐在地上的人是绝对静止的; B坐在地上的人相对地球以外的其他星体是运动的; C人造地球上的静止是相对的，运动是绝对的; D以上说法都错误2.摇动苹果树，从同一高度一个苹果和一片树叶同时从静止直接落到地上，苹果先着地.下面说法中正确的是(). A苹果和树叶做的都是自由落体运动; B苹果和树叶的运动都不能看成自由落体运动; C苹果的运动可看做自由落体运动，树叶的运…     

Ultimate Bearing Capacity of Hollow Spherical Joints Welded with Circular Pipes under Eccentric Loads

The National Swimming Center built for the 2008Beijing Olympic Games applies the polyhedron spatialframe structure, which is based on the foam physicstheory[1]. Its simple geometry is a square box of 170m×170 m×29 m. It can hold 17 000 people, theroof o…     

泵的CAD Auto选型优化算法

提出了泵的CADAuto选型优化算法．论述了泵和管路的性能曲线方程及泵安全量选定．建立了泵的选型优化约束条件及工作点的数值计算方法．针对大连水泵厂生产的泵系列进行了算例编程运算结果表明,该算法使泵选用合理．最佳地满足用户运行条件及高效率要求．     

矩形管道内充分发展热流动的可视化计算

推导了求解矩形管道内充分发展流体流动和热交换的有限差分方程,编写了相应的计算机程序,借此求得了管道横截面内速度和温度的结点值,然后利用计算机图形显示算法自动生成相应的速度和温度等值线图形．最后,对管道内充分发展热流动的特性进行了讨论．     

Multi-scaled simulation of latticed frames considering bending collapse of pipes

To consider the bending collapse of the pipes in the latticed frames, based on the multi-scale simulation, the collapsed parts of the pipe are meshed by the shell elements as micro-scaled models, and the other parts are meshed by beam elements macro-models. The incremental displacement constraint equations for the nodes on the section between the two models are established based on the plane section premise of classical beam theory. The method to introduce the constraint equations is derived based on the Updated Largrangian method. The location of the micro-model is predicted by the stress field of the beam element, and the length of the collapsed part is adjusted by the plastic energy in the micro model. Several examples are included to illustrate the efficiency and accuracy of this method.     

Effect of flushing on the detachment of biofilms attached to the walls of metal pipes in water distribution systems

Biofilm detachment caused by flushing can result in secondary contamination in drinking water distribution systems (DWDSs). To evaluate the impact of flushing on biofilm detachment, actual water supply pipes including ductile cast iron pipes (DCIPs), gray cast iron pipes (GCIPs), and stainless steel compound pipes (SSCPs) were used in this study. Real-time quantitative polymerase chain reaction and 454 pyrosequencing were used to quantify bacteria and analyse microbial community composition, respectively. The results showed that the pipe material greatly influences the resistance of a biofilm to flushing. Biofilms attached to DCIPs were able to resist quite strong flushing, while those attached to GCIPs and SSCPs were sensitive to flushing. Both flush-resistant and flush-sensitive bacteria were present in all the biofilms, but their frequency differed among the different metal pipes. Thus, the resistance to flushing of bacteria is related not only to the nature of the bacteria, but also to the pipe material. Although flushing can remove some of the biofilm and may be a good way to clean the DWDS, the shear stress needed to remove the biofilm differs among different pipe types. The results of this study provide technical support for the management and operation of DWDS.     

金塑复合水管阻力性能的测定

测定了金塑复合管的阻力性能,并与同一规格的镀锌管、聚丙烯管进行比较。结果表明,在同一流量和同一凡下,金塑复合管的阻力性能优于镀锌管和聚丙烯管,是一种性能优良的流体输送管路,符合环境保护对民用水管的要求。     

地暖用塑料管材的性能分析及选择

管材的性价比是选择地暖用塑料管材的关键.通过对地暖用塑料管材的品种和性能的对比分析知,PB管设计应力最大、可靠性最高、原料价格也最高,但抗划痕能力相对较差;PP-R管材已很少使用;XPAP管材在使用时,要充分考虑铝层与塑料间粘结剂的耐热和老化问题;PE-X和PE-RT管材较适用于地暖;PE-RT管材的综合性价比更突出.     

Collapse analysis of imperfect subsea pipelines based on 2D high-order nonlinear model

To study the collapse of imperfect subsea pipelinos, a 2D high-order nonlinear model is developed. In this model, the large deformation of the pipes is considered by raiaining the high-order nonlinear terms of strain. In addi-tion, the J2 plastic flow theory is adopted to describe the elasioplastic constitutive relations of material. The quasi-static process of collapse is analyzed by the increment method. For each load step, the equations based on the principle of virtual work are presented and solved by the discrete Newton＇s method. Furthermore, finite element simulations and full-scale experiments were preformed to validate the results of the model. Research on the major influencing factors of collapse pressure, including D/t, material type and initial ovality, is also presented.     

高压油管开裂失效分析

两件汽车柴油机高压油管在服役的过程中发生了断裂,断口学分析表明疲劳断裂是两件高压油管的主要失效机制。通过对油管表面缺陷、金相组织的观察及油管力学性能的测定确定两件油管的失效原因。