小尺寸2D密闭腔气体摆特性的有限元分析

采用有限元法,计算了小尺寸2D密闭腔中点热源引起的对流场和温度场,从而验证和解释了小尺寸密闭腔内自然对流气体的摆特性。结果表明:(1)无论是在水平状态还是在倾斜状态,在浮升力的作用下密闭腔内自然对流气体的方向总是竖直向上,具有摆的特性;(2)热源两侧原来处在同一条等温线上两点的温度不再相等,倾斜10°时,温度之差为20K;倾斜20°时,温度之差为40K。微机械气流式水平姿态传感器利用这一特性可敏感倾斜角度。     

热敏电阻的排列对传感器灵敏度的影响

采用有限元方法,借建立微机械气流式全方位水平姿态传感器敏感元件的三维模型,计算了热敏电阻在不同排列方式和不同倾斜状态下,敏感元件内温度场和流场的分布。结果表明:当两两相对的检测热敏电阻之间的距离d改变时,温度场和流场都发生变化;两两相对的检测热敏电阻处气流速度之差?v与倾角关系曲线也随d发生变化。其中,d为900μm是热敏电阻的最佳排列方式。     

A coupled-mode sound propagation model with complex effective depth

A coupled-mode sound propagation model with complex effective depth is presented,in order to involve the effect of branch line integral for acoustic field in a range-dependent waveguide.The equations of motion and continuity are used to obtain the coupled equations,which satisfy boundary conditions in the waveguide with varying topography and contain one coupling matrix.Meanwhile,the couplings between discrete and continuous spectrum are dealt with based on complex effective depth theory.Numerical simulations show that the accuracy of transmission loss is improved by the coupled mode model when eigenvalues of trapped modes are located near the branch point.The acoustic field in a non-horizontally stratified waveguide can be calculated efficiently and accurately by this model,and the energy corresponding to trapped modes,leaky modes and branch line integral can be considered adequately.     

二维周期结构有效电磁参数计算

：采用有限元方法,通过外加电流源求解周期结构中的有效电磁参数问题是一种通用的均匀化方法。该方法既可以适用禁带区域的计算,也可以适应有耗结构的计算。本文针对二维周期结构计算了有效电磁参数,并与文献[1]FDTD的计算结果进行了比较。     

单轴MEMS热膨胀流陀螺敏感机理三维有限元分析

该文提出了一种单轴微机电系统(MEMS)热膨胀流陀螺的基本结构,并揭示了其敏感机理。通过有限元法,利用COMSOL Multiphysics建立了陀螺的三维模型,在有无角速度时对陀螺敏感元件的温度场和等温线变化情况进行计算。结果表明,单轴MEMS热膨胀流陀螺具有陀螺效应,输入角速度为[-1 080 (°)/s, 1 080 (°)/s],陀螺的结构灵敏度为0.053 9 K/[(°)·s^-1],非线性度为14.13%。     

涂层厚度对喷涂层疲劳磨损寿命影响的实验研究

采用等离子喷涂制备了不同厚度的铁基涂层,采用扫描电子显微镜（SEM）表征了涂层内部和结合界面处的微观结构,采用球盘式疲劳磨损试验机分别考察了不同厚度涂层的疲劳磨损行为,采用Weibull分布分析并对比了涂层的疲劳磨损寿命。结果表明：适当地增加喷涂层的厚度可以避免整层分层失效的发生,而从在整体上提升涂层的疲劳磨损寿命。采用有限元分析（FEM）研究了涂层内部的应力分布,发现厚涂层界面剪切应力值不足薄涂层界面剪切应力的二分之一,可见显著降低界面剪切应力是较厚涂层拥有更好疲劳性能的主因。     

地质和岩土工程光纤传感监测技术综述

光纤传感器与常规传感器相比具有很大的优越性,已经成为地质和岩土工程监测领域中的研究热点。本文介绍了光纤传感监测系统的种类、基本测量原理和目前国内外的研究发展状况,并对各种传感技术的性能和特点进行了比较,指出了光纤传感监测技术应用于地质和岩土工程监测尚需研究的相关课题。     

A quantitative analysis of the travelling wave solution of the KdV-Burgers equation

By using the methods of mathematics analysis,we investigate the travelling wave solution of the KdVB equation under the assumption v~2》4μ.We prove that the travelling wave solution is quantitatively similar to the corresponding Burgers shock wave.Then we prove that the absolute error of the general asymptotic expansion is high order quantity of the small parameterε.     

Almost Fixed Points and Fixed Points of Upper [Lower] Semicontinuous Multimap on Locally G-convex Spaces

In this paper, we use the well known KKM type theorem for generalized convex spaces due to Park (Elements of the KKM theory for generalized convex spaces, Korean J. Comp. Appl. Math., 7(2000), 1-28) to obtain an almost fixed point theorem for upper [resp., lower] semicontinuous multimaps in locally G-convex spaces, and then give a fixed point theorem for upper semicontinuous multimap with closed Г-convex values.     

无人机直喷发动机谐振进气系统设计及仿真分析

本文针对一无人机用四缸两冲程汽油直喷发动机,应用GT-Power软件建立了仿真模型,并通过对气缸压力和发动机扭矩的仿真结果与实验数据进行对比,验证了所建模型的合理可用性。运用亥姆霍兹理论设计了谐振进气系统,并利用软件自带的优化工具,分析了谐振器及进气系统管道长度对发动机动力性能的影响。仿真结果表明,进行参数优化后,该谐振进气系统使得无人机动力性能得到进一步提升。