一种适用于多尺度边缘提取的双正交小波的构造

该文构造了一种适用于多尺度边缘提取的完全重构滤波器组,实验结果证实利用这种滤波器组能用更少的计算工作量提取信号的基本特征。     

基于综合特征一致性的感兴趣目标检测

感兴趣目标检测是模式识别的关键部分.文中研究了一种新的检测感兴趣目标的方法.首先将相位子带滤波器组输出的图像局部信息表示为单个特征的集合,该集合中的若干单个特征组成了综合特征;然后在综合特征的基础上给出了综合特征一致性函数,并用噪声估计进行修正;最后利用该函数对复杂自然背景中的感兴趣目标进行检测.实验结果表明,该算法能够滤除复杂的自然背景,有效地检测出感兴趣目标,且具有通用性.     

翅片螺距对折齿型螺旋翅片管束性能的影响

为了提高平齿型翅片管的强化传热效果,通过改变其锯齿的扭转方向和偏折角度得到了折齿型螺旋翅片管。利用数值模拟和模化试验相结合的方法对基管外径分别为38 mm和51 mm的折齿型螺旋翅片管束进行研究,得到了翅片螺距对折齿型螺旋翅片管束的换热与阻力性能的影响规律和最优翅片螺距。结果表明:翅片螺距P_f在3.63~8.47 mm范围内,空气侧Nusselt数Nu随P_f增大呈先递增后递减的趋势;当P_f大于6.35 mm时,翅片螺距增大对Nu的影响相对已不明显;空气侧Euler数Eu随P_f增大而减小。对于基管外径分别为38 mm和51 mm的折齿型螺旋翅片管束,P_f为6.35 mm时其性能指标Nu·f ^-1/3均最大,因此P_f=6.35 mm是最优翅片螺距。     

非平整倾斜表面上流动液膜的影响因素分析

基于流体体积函数法(VOF),分别从液体物性和液相入口流速等因素对非平整倾斜表面上的液膜流动特性进行数值模拟,得出流体黏度的增大可增大液膜厚度并降低液膜整体流动速度,但不影响液膜与壁面之间的相位角;流体表面张力影响液膜与壁面之间的相位差及液膜的均匀性;液相入口雷诺数的增大可以增大液膜厚度,当雷诺数增大到一定程度时,液膜厚度不再有明显的变化,且液膜表面趋于光滑。研究结果表明:液膜的流动形式由液体各项物性和液相入口流速共同决定。     

Soret and Dufour effects on free convection boundary layers over an inclined wavy surface in a porous medium

This work studies the heat and mass transfer characteristics of natural convection near a vertical wavy cone in a fluid saturated porous medium with Soret and Dufour effects. The surface of the wavy cone is kept at constant temperature and concentration. The governing equations are transformed into a set of coupled differential equations, and the obtained boundary layer equations are solved by the cubic spline collocation method. The heat and mass transfer characteristics are presented as functions of Soret parameter, Dufour parameter, half angle of the cone, Lewis number, buoyancy ratio, and dimensionless amplitude. Results show that an increase in the Dufour parameter tends to decrease the local Nusselt number, and an increase in the Soret parameter tends to decrease the local Sherwood number. Moreover, a greater half angle of the cone leads to a greater fluctuation of the local Nusselt and Sherwood numbers with the streamwise coordinates.     

一种单载波宽带信号非线性均衡技术

针对单载波宽带信号均衡难以收敛的问题,研究了一种基于子带分解与重构的宽带非线性均衡技术。综合利用复数子带滤波器组与判决反馈均衡器理论,给出了两种具有模式切换功能的宽带非线性均衡结构,基于最小均方算法推导了它们的均衡权值迭代更新公式,分析比较了两种结构在不同均衡模式下的收敛特点。仿真证明基于子带技术的宽带非线性均衡能适用于群时延较严重的信道,且比传统全频带均衡具有更好的收敛效果和更低的计算复杂度。     

硅基正弦波纹微通道内的流动阻力特性

硅基正弦波纹微通道在微尺度强化换热、微流体器件中均有重要运用,而目前尚未见有关于其内部流动特性的实验报道。利用标准微机电系统（MEMS）工艺在硅基芯片上加工制成一系列具有不同相位差和周期、当量直径为160 μm的正弦波纹微通道,通过实验研究了其内部流动阻力特性。研究表明：正弦波纹微通道较平直微通道阻力均有增加,且增加幅度与波纹微通道两侧壁的相位差和周期有关。对于周期相同的波纹微通道,两侧壁相位差越大,阻力也越大。对于相位差相同的波纹微通道,周期对阻力的影响则较为复杂：当相位差为0时,呈现出周期越大、阻力越小的趋势（除最小周期通道外）;当相位差为π时,呈现出周期越大、阻力越大的趋势。研究还发现：随着周期减小,相位差对阻力的影响减小,当周期缩短至0.5 mm时,相位差为0和π的波纹微通道内的阻力特性曲线几乎重合。     

刚性波纹面与柔性波纹面传热及流动特性

采用大涡模拟方法,对流体在刚性及柔性波纹面上的流动与传热特性进行了数值研究。结果表明:对于刚性波纹面,当振幅与波长比值(a/λ)较小时,波谷区域无回流现象;当a/λ增大至0.03时,波谷区域出现回流区,且回流区域随波幅的增加而增大;波纹面上坡部位沿展向出现较高Nusselt数的斑块;当a/λ从0.01增至0.04时,时均Nusselt数提高了近63.5%,综合系数增加了0.5112。对于柔性波纹面,其压力分布也呈现周期性变化;且在上坡位置也出现较大Nusselt数斑块;当a/λ从0.01增至0.04时,时均Nusselt数值提高了173.1%,综合系数增加了1.1232。与刚性波纹面相比,在消耗相同流体输送泵功时,柔性波纹面具有更好的传热效果。     

Mixed convective flow of two immiscible viscous fluids in a vertical wavy channel with traveling thermal waves

The problem of fully developed laminar mixed convection flow in a vertical wavy channel filled with two immiscible viscous fluids is studied analytically. Non‐linear equations governing the motion have been solved by linearization technique, wherein the flow is assumed to be in two parts; a mean part and a perturbed part. Exact solutions are obtained for the mean part and a perturbed part is solved using long wave approximation. Separate solutions are matched at the interface using suitable matching conditions. Numerical results are presented graphically for the distribution of velocity and temperature fields for varying physical parameters such as Grashof number, viscosity ratio, width ratio, and conductivity ratio. The effect of these parameters on the physical characteristics such as Nusselt number and skin friction at the walls is studied. It is found that Grashof number, viscosity ratio, width ratio, and conductivity ratio enhance the velocity parallel to the flow direction. Reversal effect is observed on the velocity which is perpendicular to the flow direction. The Nusselt number remains invariant on Grashof number. As the width ratio decreases, the Nusselt number decreases at the right wall and increases at the left wall and reversal effect is observed for variations of conductivity ratio. The skin friction increases at the left wavy wall and decreases at the right wavy wall as the Grashof number increases. © 2011 Wiley Periodicals, Inc. Heat Trans Asian Res; Published online in Wiley Online Library ( wileyonlinelibrary.com/journal/htj ). DOI 10.1002/htj.20379