动态有限单元法对摩托车刚架的动力分析

本文采用了各阶动态约束模态函数而组成的平面刚架结构有限单元的各阶动态形函数矩阵及各阶单元特性表达式,利用它们可以准确地计算出摩托车的各阶动特性,进而可求出在各种载荷下的各阶动位移与动应力分量,最后将各阶动应力分量迭加,即可准确地求出动位移及动应力响应。无疑这对摩托车的优化设计是十分有意义的。     

Frequency-dependent dynamic effective properties of porous materials

The frequency-dependent dynamic effective properties (phase velocity, attenuation and elastic modulus) of porous materials are studied numerically. The coherent plane longitudinal and shear wave equations, which are obtained by averaging on the multiple scattering fields, are used to evaluate the frequency-dependent dynamic effective properties of a porous material. It is found that the prediction of the dynamic effective properties includes the size effects of voids which are not included in most prediction of the traditional static effective properties. The prediction of the dynamic effective elastic modulus at a relatively low frequency range is compared with that of the traditional static effective elastic modulus, and the dynamic effective elastic modulus is found to be very close to the Hashin-Shtrikman upper bound.     

单一水文站洪水波计算方法

本文介绍应用水力学方法计算洪水波绳套曲线。应用动力波模式的格戈夫方法,精度较高,特别适用于洪水期流量涨落变幅较大的场合,应用扩散波模式的琼斯方法,易于掌握和计算。以上两种方法都只需要用一个水文站的资料即可计算。对两种方法计算所得结果,用实测原型资料进行了验证。本文还对影响绳套曲线变化的惯性项进行了分析、探讨。     

喷淋液滴在空气环境下的运动特性

本文以喷淋液滴在空气环境下运动特性为工程背景,建立单个液滴在常温、常压空气环境中的动量方程,分析液滴沉降特性、追赶特性及运动轨迹行为。计算结果表明,不同喷淋液滴初始条件下,短时间内存在重力大于曳力和重力小于曳力两种情况,但最终减速液滴均会达到受力平衡状态;液滴离开喷淋头后,垂向位移均迅速增大,液滴粒径越大、初始速度越大,垂向位移增长的速率也越大,达到相同位移的用时越短;液滴尺寸、初始速度相差越大,液滴追赶所用的时间越短,追赶位移越小,液滴尺寸、初始速度越接近,液滴追赶所用的时间越长,追赶位移越大;液滴初始速度越大、初始直径越大、喷射角度越大,横向速度消失越慢,达到的横向位移越大,喷射液滴覆盖的面积也越大。计算结果有助于优化工程实际中喷淋系统的设计与布置。     

熔池中液态金属自由表面温度分布与液面形状研究

根据Ｙｏｕｎｇ－Ｌａｐｌａｃｅ方程对液态铀溶池的自由表面进行了数值计算。得到了表面凹陷与表面温度分布的关系。阐明了电子枪加热金属表面时出现的凹陷是由于原子蒸汽对液态金属表面反冲压力所引起的，而不是电子束的冲量造成的观点。对不同最高温度及不同熔池宽度的液态铀熔池表面凹陷形状进行了计算。     

一种大动态检测输入前端设计

一种基于小信号处理、无源网输入、数字化处理、智能化操作的方法,以求获得较好的灵敏度和极大的测量动态范围的测量前端电路设计。     

压缩系统对温度突升响应的动态分析

基于时间滞后概念,建立了压缩系统动态响应分析的通用模型,并对温度突升条件下多级轴流压缩系统的动态响应及气动稳定性进行了详细的数值分析。对两个算例的分析,结果表明了本文新模型的可行性。     

动态核的形态分解联想算法及抗随机噪声研究

在灰度图像分解算法和动态核形态联想记忆网络的基础上,提出了一种新的联想记忆算法--动态核的形态分解联想算法.该方法显著地提高了联想记忆抗随机噪声的能力,较好地解决了灰度图像在含噪时的联想记忆和识别的问题,从而给出了一种恢复含噪灰度图像的途径,并把该方法推广到了彩色图像的处理.通过实验,验证了该方法的良好性能,取得了理想的结果.     

An efficient second‐order characteristic finite element method for non‐linear aerosol dynamic equations

In the paper we consider the non‐linear aerosol dynamic equation on time and particle size, which contains the advection process of condensation growth and the process of non‐linear coagulation. We develop an efficient second‐order characteristic finite element method for solving the problem. A high accurate characteristic method is proposed to treat the condensation advection while a second‐order extrapolation along the characteristics is proposed to approximate the non‐linear coagulation. The method has second‐order accuracy in time and the optimal‐order accuracy of finite element spaces in particle size, which improves the first‐order accuracy in time of the classical characteristic method. Numerical experiments show the efficient performance of our method for problems of log‐normal distribution aerosols in both the Euler coordinates and the logarithmic coordinates. Copyright © 2009 John Wiley & Sons, Ltd.