高雷诺数下双圆柱绕流的数值模拟

本文使用表面涡法研究高雷诺数下不同排列方式双圆柱绕流的流动状态，计算了双圆柱在并列、串列及级列的情况下的各种流动结构，涡街的变化及作用在圆柱上的受力情况。本文结果清楚地描述了双圆柱绕流复杂的流动状况，计算结果与实验显示的流动状况十分相似，斯特罗哈数和阻力系数与实验结果符合得很好。     

EFFECT OF STREAMLINE CURVATURE AND SOME OTHER CONDITIONS ON THE TURBULENT STRUCTURES IN THE OTHER REGION OF AN OBSTACLE

ＥＦＦＥＣＴＯＦＳＴＲＥＡＭＬＩＮＥＣＵＲＶＡＴＵＲＥＡＮＤＳＯＭＥＯＴＨＥＲＣＯＮＤＩＴＩＯＮＳＯＮＴＨＥＴＵＲＢＵＬＥＮＴＳＴＲＵＣＴＵＲＥＳＩＮＴＨＥＯＴＨＥＲＲＥＧＩＯＮＯＦＡＮＯＢＳＴＡＣＬＥＬｉｕＳｈｉ－ｈｅ（ＷｕｈａｎＵｎｉｖｅｒｓｉｔ...     

重新认识摩天大楼的安全性--9·11撞击事件给人的反思

9·11恐怖撞击事件,促使人们重新认识摩天大楼的安全性,由于这类建筑规模越大,其安全性受到的损害就越大,同时也带来其他方面的问题.因此,为减少灾害发生后的损失,必须控制其规模,确保摩天楼建设有序进行.     

Vorticity field structure associated with the 3D Tollmien-Schlichting waves

Details of the vorticity field structure associated with the 3D Tollmien-Schlichting waves have been examined based upon the recent numerical studies of the subject. First, a single obliquet-s wave has been found to have the velocity component parallel to the wave front playing an overall dominant role, in particular, to create the longitudinal vorticity. The so-called Benney-Lin longitudinal vortices are then demonstrated to be, in fact, a minor consequence compared with the localized longitudinal vorticity field and its periodic pumping. Finally, the formation of the longitudinal vorticity field in the fundamental- and subharmonic-mode interactions is explained. The research reported in this paper has been supported in part by Bundesministerium für Forschung und Technologie and by Deutsche Forschungsgemeinschaft. The major part of the paper has been presented at the Third Asian Congress of Fluid Mechanics, 1–5 September 1986, in Tokyo, as a General Lecture by the senior author, FRH.     

Response of the seated human body to whole-body vertical vibration: biodynamic responses to sinusoidal and random vibration

The dependence of biodynamic responses of the seated human body on the frequency, magnitude and waveform of vertical vibration has been studied in 20 males and 20 females. With sinusoidal vibration (13 frequencies from 1 to 16 Hz) at five magnitudes (0.1–1.6 ms^? 2 r.m.s.) and with random vibration (1–16 Hz) at the same magnitudes, the apparent mass of the body was similar with random and sinusoidal vibration of the same overall magnitude. With increasing magnitude of vibration, the stiffness and damping of a model fitted to the apparent mass reduced and the resonance frequency decreased (from 6.5 to 4.5 Hz). Male and female subjects had similar apparent mass (after adjusting for subject weight) and a similar principal resonance frequency with both random and sinusoidal vibration. The change in biodynamic response with increasing vibration magnitude depends on the frequency of the vibration excitation, but is similar with sinusoidal and random excitation.     

Response of the seated human body to whole-body vertical vibration: discomfort caused by sinusoidal vibration

Frequency weightings for predicting vibration discomfort assume the same frequency-dependence at all magnitudes of vibration, whereas biodynamic studies show that the frequency-dependence of the human body depends on the magnitude of vibration. This study investigated how the frequency-dependence of vibration discomfort depends on the acceleration and the force at the subject–seat interface. Using magnitude estimation, 20 males and 20 females judged their discomfort caused by sinusoidal vertical acceleration at 13 frequencies (1–16 Hz) at magnitudes from 0.1 to 4.0 ms^? 2 r.m.s. The frequency-dependence of their equivalent comfort contours depended on the magnitude of vibration, but was less dependent on the magnitude of dynamic force than the magnitude of acceleration, consistent with the biodynamic non-linearity of the body causing some of the magnitude-dependence of equivalent comfort contours. There were significant associations between the biodynamic responses and subjective responses at all frequencies in the range 1–16 Hz.

Practitioner Summary: Vertical seat vibration causes discomfort in many forms of transport. This study provides the frequency-dependence of vibration discomfort over a range of vibration magnitudes and shows how the frequency weightings in the current standards can be improved.     

基于MEMS三轴加速度传感器的摔倒检测

摔倒作为人体活动的一部分,是影响人体健康的一大因素,尤其对病人和老年人而言,摔倒检测至关重要。基于MEMS三轴加速度传感器采集的人体活动加速度信号,提出了一种基于固定阈值的信号幅度向量滑动平均法SVMSA。该方法根据人体活动时的加速度信号特征,利用预先设定的阈值对加速度信号幅度向量SVM的滑动平均SVMSA进行判决,同时使用差分信号幅度域DSMA区分快速跑步等剧烈运动,准确实现了人体的摔倒检测。主要优势在于分析并区别了人体快速跑步等剧烈运动对摔倒检测的影响。通过对8位实验者的测试,该算法实现了94.4%的精确度。实验表明该算法能够较为准确地实现人体的摔倒检测。     

一种自适应改进曲率扩散超声图像滤波方法

针对图像尤其是医学超声图像的边缘模糊或者缺失对图像进一步处理带来的影响,同时由于传统改进曲率扩散方程无法自适应以及迭代时间长,本文提出了一种结合高斯滤波的参数自适应的改进曲率扩散方法,并且使用统计学中的绝对偏差中值自动调整梯度阈值参数。该方法能在保留改进曲率扩散方程去噪能力的同时有效地保留图像边缘细节信息,同时减少了滤波过程中的迭代次数,从时间复杂度的方面提高了方法的效率。另外,自适应梯度阈值的采用进一步提高了改进曲率扩散方程保留图像细节信息的能力。实验结果表明,结合高斯滤波的参数自适应改进曲率扩散方法继承了改进曲率扩散的优点,同时又减少了人工干预,提高了去噪效率。     

谐波法复杂周期信号周期测量

利用复杂周期信号频谱存在大量等间隔幅度起伏的谐波分量.提出了复杂周期信号的谐波法周期测量.谐波法之FT-Abs-IFT(FAIF)是周期信号频谱包络的反傅里叶变换,输出为频谱包络对应时域信号与周期冲击信号的卷积.其最大值是等幅度或起伏幅度(噪声条件下)的周期冲击信号,通过门限栓测和周期测量得到信号周期(或频率).最后通过与常用周期信号测量方法(同态滤波法、自相关法和AMDF)的仿真比较,表明对于复杂周期信号,谐波法之FAIF测量精度高,误差率低和良好的抗噪性能.     

基于CORDIC算法的360°角度传感器的设计

一维霍尔板型角度传感器无法测量0～360°的角度,采用4个霍尔器件的联合测角技术和CORDIC算法可实现0～360°范围内的角度测量。文章详细描述了4个霍尔器件联合测角技术的测角原理及实现算法,并引入了符号幅值表示法,即先利用正弦和余弦的幅值进行0°～90°范围内的反正切CORDIC运算,再根据正弦和余弦正负号(符号)的不同组合实现角度从0°～90°到0°～360°的映射。Modelsim平台仿真验证了该方法的准确度和精度,仿真误差小于0.01%,实测总误差不大于0.05°。