蓄能式液压发射装置设计与分析

为了控制传统往复泵式武器发射装置发射武器时产生的剧烈喷注噪声,基于空气弹簧理论,提出了蓄能式液压平衡发射装置的设计方案.设计方案采用高压气体作为能量存储媒介,易于工程实现.基于水压平衡式发射模块的数学模型,建立了蓄能式发射装置发射武器的内弹道模型,并开展了仿真计算.仿真表明改进发射装置可以顺利完成武器发射任务,发射时间...     

单向联轴器楔紧过程平面及三维数值对比研究

以具有对数螺旋线型面特征的综合式液力变矩器单向联轴器为研究对象,为考察其在瞬态楔紧过程中内外环及滚子等各部分应力分布状态特性,基于显式动力学理论进行了二维平面应变和三维有限元动力学分析,分别从二维和三维的角度对这一动态过程进行了数值模拟.对2种方法仿真结果的对比分析表明,三维分析的结果所获得的各部件轴向的应力分布信息弥...     

极性分子多层修饰的金属Ni核心核壳微粒的电流变液

通过研究TiO2包覆不同极性分子修饰金属Ni核心核壳微粒的结构及其电流变液的性能,分析Ni/TiO2基核壳结构微粒电流变液性能与极性分子种类、复合修饰以及所加电场强度的关系。结果表明,对同成分电流变液随极性分子的加入,其强度均出现不同程度的增加,多层修饰利于电流变液剪切强度的提高,十二烷基苯磺酸钠(SDBS)可显著提高电流变液的沉降稳定性。     

Study on Energy Stored in Thin Layers of MEMS Ultrasonic Resonance Separator

The particles suspending in liquid suffer acoustical radiation force from ultrasonic field. The force may cause particles movement and has special advantage to separate particles from liquid in Micro Electro Mechanical Systems （MEMS）. It is important to improve the energy stored in liquid layer so as to increase separation ability for decreasing drive demand in MEMS. Resonance may hugely increase the magnitude and generally be employed in micro separator. The summits of admittance spectrum show the resonance frequencies. It may come from resonance in one layer or multi layers in micro separator. This paper studies the difference of energy stored in layers at each rein frequency. It provides the way to select the most effect separation frequency other than admittance spectrum.     

大功率液力变矩器叶轮强度有限元分析

为解决履带车辆大功率液力变矩器在高转速工况下的叶轮强度问题,基于单向流固耦合(FSI)理论,建立了液力变矩器叶轮强度分析模型.采用全局守恒插值算法,实现了流场网格节点上的流体压力载荷到结构网格节点的插值传递.结合惯性离心载荷,采用静力学分析的方法,对某型液力变矩器叶轮,进行了2种载荷共同作用下的有限元强度分析,得到了其...     

车辆座椅变刚度变阻尼减振的研究

基于双磁流变阻尼器构建了变刚度变阻尼的座椅半主动减振系统,建立了人体-座椅的2自由度动力学模型;对该半主动变刚度变阻尼系统的座椅减振方式采取了开关控制算法.将系统模型在MATLAB—SIMULINK中进行相应的建模仿真,并与被动减振模型进行对比分析.仿真结果表明,人体加速度均方根值要减小72.8%,人体垂直位移均方根值要减小18.4%,大幅度降低了人体所受的振动强度,能有效地改善座椅的减振效果.     

CZ法硅晶体生长过程中热输运和流体流动的数值研究

A global analysis of heat transfer and fluid flow in a real Czochralski single silicon crystal furnace is developed using the FLUENT package.Good agreement was obtained for comparisons of the power and crystal growth speed between the simulation and experimental data,and the effect of the length of the crystal on heat transfer and fluid flow was analyzed.The results showed that T_max increases and its location moves downward as the crystal length increases.The flow pattern in the melt does not change until the crystal grows to 900 mm.As the crystal length increases,the flow pattern in the first gas area only changes when the crystal length is less than 700 mm,but the flow pattern in the second area changes throughout the growth process.     

Queue Lengths and Waiting Times for Multiserver Queues with Abandonment and Retrials

We consider a Markovian multiserver queueing model with time dependent parameters where waiting customers may abandon and subsequently retry. We provide simple fluid and diffusion approximations to estimate the mean, variance, and density for both the queue length and virtual waiting time processes arising in this model. These approximations, which are generated by numerically integrating only 7 ordinary differential equations, are justified by limit theorems where the arrival rate and number of servers grow large. We compare our approximations to simulations, and they perform extremely well.     

宽带网络流媒体技术的应用与发展

流媒体技术是在数据网络上以流的方式传输多媒体信息的技术。近年来,随着宽带网络的发展和用户需求的驱动,流媒体技术和相关的应用得到越来越多的关注,被认为是未来高速宽带网络的主流应用之一。文中介绍了流媒体的概念与特点,深入分析了流媒体系统及其关键技术,研究了流媒体技术在宽带网络中的应用及在国内外的发展情况,对流媒体技术在发展中遇到的问题做了说明。还针对国内目前的宽带网络现状提出了流媒体技术的应用和发展建议。     

基于CSD/CFD舵面气动力流固耦合仿真分析

空空导弹空气舵面与气动力存在流固耦合作用。采用ANSYS Workbench 14.5对空气舵面与气动力进行了流固耦合仿真分析,研究了攻角和马赫数对舵面振动位移的影响。研究表明,舵面振动位移频率受攻角和马赫数的影响较小,舵面振动位移幅值随攻角和马赫数的增大而增大,并呈非线性关系。低马赫数范围内,飞行速度的变化对舵面振动位移的影响更为明显。攻角为30°,马赫数为3时,舵面振动位移曲线更趋向于等幅振动,舵面趋向于颤振临界状态。