定解问题的可视化教学设计探讨

通过对一维弦振动的定解问题的计算机动态仿真,比较了不同定解条件下弦振动的视觉效果,讨论了相应的课外仿真设计.教学设计中突出了将传统的理论推导与计算机编程技术结合起来的教学思路,注重培养学生发现、分析和解决问题的兴趣和能力.     

参数弱向量平衡问题解集的似Holder性和相依导数

本文研究了一类参数弱向量平衡问题解集的似Hölder性和相依导数. 首先, 讨论了该问题的一类实值间隙函数的Lipschitz连续性和Hadamard方向可微性. 然后, 借助这些性质, 建立了该问题解集的似Hölder性和Hölder连续性以及相依导数的具体表达式.     

微机械框架陀螺仪的动力学分析

本文根据欧拉动力学方程导出微机械框架陀螺仪的动力学方程，给出陀螺仪的运动规律，并探讨惯性质量对测量灵敏度的影响。     

基于格子boltzmann方法固井环空介观微间隙气体窜槽研究

固井环空微间隙气体窜槽现象直接影响固井质量与油田生产,准确地描述固井环空微间隙气体窜槽的流动规律是有效控制气体窜槽的核心与"瓶颈"问题.从微观粒子运动角度出发,基于格子Boltzmann方法建立了固井环空微间隙气体粒子流动模型.选取大庆油田某区块计算模拟不同环空压差下微间隙内气体粒子流动速度分布规律,计算结果揭示了固井气窜气体粒子在微环间隙内流动的本质,为后续固井气窜问题的研究开辟新的思路.     

Simultaneous effects of magnetic field and space porosity on compressible Maxwell fluid transport induced by a surface acoustic wave in a microchannel

Peristaltic motion induced by a surface acoustic wave of a viscous, compressible and electrically conducting Maxwell fluid in a confined parallel-plane microchannel through a porous medium is investigated in the presence of a constant magnetic field. The slip velocity is considered and the problem is discussed only for the free pumping case. A perturbation technique is employed to analyze the problem in terms of a small amplitude ratio. The phenomenon of a “backward flow” is found to exist in the center and at the boundaries of the channel. In the second order approximation, the net axial velocity is calculated for various values of the fluid parameters. Finally, the effects of the parameters of interest on the mean axial velocity, the reversal flow, and the perturbation function are discussed and shown graphically. We find that in the non-Newtonian regime, there is a possibility of a fluid flow in the direction opposite to the propagation of the traveling wave. This work is the most general model of peristalsis created to date with wide-ranging applications in biological, geophysical and industrial fluid dynamics.     

Multipacting analysis in micro-pulse electron gun

Modeling multipacting to steady state saturation is of interest in determining the performance of the micro-pulse electron gun. In this paper, a novel method is proposed to calculate the multipacting resonance param- eters for the gun. This method works well, and the 2-D simulation results suggest that steady state saturation can be achieved in the gun. After saturation the transition from two-surface multipacting to single-surface multipacting occurred, and an extensive range of electron emission time is a suggested way to avoid this kind of transition.     

HOMOCLINIC SOLUTIONS FOR A CLASS OF SECOND ORDER NEUTRAL FUNCTIONAL DIFFERENTIAL SYSTEMS

By means of an extension of Mawhin’s continuation theorem and some analysis methods, the existence of a set with 2kT-periodic solutions for a class of second order neutral functional differential syste...     

微构件材料力学性能测试方法

随着MEMS的商业化进程,微构件材料力学性能的研究成为越来越重要的一个课题。微小试件的制备、安装、夹持、微驱动、高分辨率的载荷和位移测量等技术问题都是对微构件材料力学性能测试的很大挑战,很多传统的测试方法和装置已经不再适用了。近十几年,国内外学者发展了一些微构件材料力学性能的研究方法,来测量微构件的弹性模量、屈服强度、断裂强度、残余应力和疲劳强度等。本文从实验系统的集成度出发,将这些测试方法大致分为片外测试和片上测试两类。本文对单轴拉伸法、纳米压痕法、鼓膜法、微梁弯曲法和衬底曲率法等典型的片外测试方法和一些典型的片上测试方法进行了介绍,并比较了各自的优缺点。     

大气气溶胶粒径分布的多波长激光雷达反演

提出一种基于正则化方法改进的气溶胶微物理特性反演算法,通过引入模式半径范围作为先验约束,并对差异最小值附近的解进行平均,以解决反演时存在的欠定问题。对1500组不同类型的气溶胶粒径分布进行仿真,测试了所提反演算法对气溶胶微物理特性参数的反演精度与稳定性。考虑在20%随机高斯噪声的影响下,90%以上气溶胶的有效半径、体积浓度和表面积浓度反演相对误差可被控制在±33%、±45%和±50%范围内。误差统计结果表明,所提算法基于多波长的气溶胶光学特性,可实现对气溶胶粒径分布的可靠反演。     

微螺旋炭纤维的制备、微观结构及性能

以乙炔为碳源,镍粉为催化剂,噻吩作为助催化剂,采用化学气相沉积法制备微螺旋炭纤维.通过扫描电子显微镜、X射线衍射、激光拉曼光谱、元素分析和热失重分析等分析手段,研究了微螺旋炭纤维的制备工艺,考察了微螺旋炭纤维的形貌、微观结构和性能.结果表明:微螺旋炭纤维具有双螺旋结构,单根纤维存在左旋和右旋两种螺旋方向以及圆形和扁形两种纤维截面,同时也可以观察到一些特殊形状的微螺旋炭纤维.微螺旋炭纤维主要由C、Ni、S、H元素组成,且其纤维表面全部由碳元素组成.微观结构整体有序度较差,存在一定量的无定形碳和晶体缺陷.微螺旋炭纤维具有较高的抗氧化性.