基于机械共振的声谱分析技术

A model for the accurate measurement of low frequency sound spectrum is put forward and a simplified experimental device is built. Based on the principle of mechanical resonance, the natural frequency ...     

基于Mathematica的弹簧摆内共振现象研究

利用Mathematica软件模拟弹簧摆的内共振现象,得出了弹簧摆的运动轨迹、振动曲线和能量曲线,计算机模拟的结果与实验结果相吻合.     

基于振动共振的随机共振控制

分析了非线性双稳系统在高、低两种不同频率信号作用下的动力学特性,给出了高频信号参数与双稳系统输出信号的信噪比和功率谱放大率关系的解析表达式,提出了基于振动共振的随机共振控制方法.理论分析和数值仿真结果表明,通过调节高频信号的幅值或频率大小,能有效地控制双稳系统输出信号的信噪比和功率谱放大率.     

基于Matlab的弹簧摆内共振与混沌运动研究

针对二维弹簧摆中弹簧型和摆型的振动两种模态,建立了系统的动力学方程.运用Matlab对该方程进行了数值求解,绘制了弹簧摆的演化曲线、相图以及运动轨迹,并对系统进行了动力学行为分析.结果发现:弹簧摆动与弹簧振子的固有频率之比f为1/2且初始摆角极小时,弹簧摆有内共振现象且作准周期运动;在初始摆角不变时,通过改变参数f,弹...     

外力驱动下耦合弹簧振子的法诺共振

法诺共振是物理体系中普遍存在的一种非对称共振现象,它最早起源于量子物理,其微观图像是原子谱线中窄的分离态与宽的连续态之间的相干干涉.本文利用经典力学体系中两个弹簧振子的耦合,使其中一个弹簧振子受到周期性外力的驱动,成功类比了量子力学中的法诺共振现象.通过分析每个弹簧振子的动力学方程,严格求解它们的振动公式,从而得到每个...     

三维弹簧摆的内共振特性分析

通过理论推导和MATLAB数值计算分析了三维弹簧摆的内共振特性,发现在一定条件下,三维弹簧摆在水平面内投影的运动可以近似为不断偏转的线段.通过分析三维弹簧摆在水平面内投影运动的极角,发现其在一段时间内在某一定值附近变化不大;在微振动情形下,极角的变化值与初始条件的变化满足线性关系.     

弹簧摆的内共振特性分析

首先提出了一种弹簧摆模型,通过谐波平衡法对弹簧摆的内共振现象进行了解析处理,得到了弹簧摆内共振条件以及X、Z两模态能量之间的转换关系.再利用数值模拟得到弹簧摆内共振时的时序图、相图、轨迹图、能量图以及内共振耦合区域图等,分析表明,解析和数值模拟的结果与实验结果吻合一致.     

弹簧摆内共振现象的实验研究

用视频摄像和计算机技术从实验上研究了弹簧摆的内共振现象。从系统的势能出发，讨论了弹簧摆的运动规律。通过实时记录摆球的位置，得了不同初始条件下，弹簧摆振动的位移曲线、能量曲线和摆球运动的轨迹。实验结果展示了理论与实验的一致性。     

利用Tracker软件研究有摆线弹簧摆内共振现象

利用Tracker软件追踪和分析了有摆线弹簧摆的内共振现象,实时描绘了内共振的振动位移图、相图、轨迹图和能量图,实验表明起振角对径向振动能有较大影响,摆线可以取代部分等长弹簧实现内共振,拟合计算的径向和横向振动的固有频率与理论结果一致。     

扭转超声振动系统中局部共振的研究

本文从扭转振动波动方程出发,推导出了具有类圆锥过渡段的复合阶梯型扭转变幅杆的频率方程解析表达式。从实验和理论上对该复合变幅杆的谐振频率随杆细端长度和直径的变化进行了测量和计算。通过对比,证明了复合振动系统中局部扭转共振现象的存在,并得到了其产生条件。     

基于悬臂梁调谐技术的光纤光栅无源振动监测

采用匹配光纤光栅设计了一种结构简单的振动信号无源监测装置.该装置利用悬臂梁调谐技术能够将微小振动信号转化为光电探测器可探测的光强信号,利用示波器实现实时监测.实验中对振幅为3mm的简谐振动信号进行了监测,测量结果与振动频率一致,可测量7～20Hz的振动,信噪比不低于14.9dB.监测频率受限是因为悬臂梁的性质,如采用金属材料或者采用齿轮组对转子进行减速,该装置可探测更高的频率.     

The Effect of Cooling Mode on Slow Crack Growth Resistance of Polyethylene Pipe

High-density polyethylene (HDPE) pipes have been widely used as gas or water transport pipes owing to their comprehensive advantages. One of the principal failure modes determining pipe service lifetime is slow crack growth (SCG) with the crack occurring first at the inner surface due to the slow cooling rate of the pipe's inner wall during polyethylene (PE) pipe extrusion. In order to change the conventional cooling mode and increase the cooling rate in the inner wall of PE pipe during extrusion, a novel extrusion equipment was designed and manufactured by our research team. For this paper, compressed air as a cooling medium was introduced through the interior of the hot extruded pipe during its extrusion to realize the quick inner wall cooling, and the effects of the inner wall's cooling rate on the microstructure and mechanical properties of the PE pipe were investigated. The experimental results showed that simultaneously cooling of both the outer and inner walls could decrease the difference in the solidification rate across the pipe and reduce the residual internal stresses in PE pipe. The quick cooling of the inner wall of the extruded pipe could also decrease the PE crystal thickness, and increase the number of tie molecules in the inner wall, which is a key parameter determining the resistance to SCG. As a result, compared to the PE pipe produced by the conventional extrusion, the crack initiation time of the PE pipe manufactured by the novel method increased from 27 h to 45 h and the crack growth rate was slower.     

The Effectiveness of Oral Resonance Therapy on the Perception of Femininity of Voice in Male-to-Female Transsexuals

Ten male-to-female transsexuals participated in five sessions of oral resonance voice therapy targeting lip spreading and forward tongue carriage. Acoustic analysis of recordings made pre- and posttherapy found that participant formant frequency values (F1, F2, and F3, from the vowels /a/, /i/, and /mho/), as well as fundamental frequency (F0), underwent a general increase posttherapy. F3 values, in particular, increased significantly posttreatment. Trends in listener ratings of these recordings showed that the majority of participants were perceived to sound more feminine following treatment. Participants' self-ratings of their voices pre- and posttreatment also indicated that participants perceived their voices as sounding more feminine and that they were more satisfied with their voices following treatment. The present study supports the findings of previous studies that have demonstrated that resonance characteristics in male-to-female transsexuals can be changed to more closely approximate those of females through oral resonance therapy. This intervention study also demonstrates that a spontaneous increase in F0 is achieved during the course of therapy. Further, this study provides preliminary evidence to suggest that oral resonance therapy may be effective in increasing femininity of voice in male-to-female transsexual clients.     

基于DIS系统对弹簧牵动磁体振动产生电磁感应对应参量研究

使用悬挂螺旋弹簧牵动磁体振动,在线圈内产生感应电动势的方法,将弹簧的机械振动转换为电磁振动,使弹簧机械振动的各参量转换为一一对应的电磁参量,用DIS数字化信息系统测量各电磁参量,从而展开分析研究。     

The Effect of Talc on the Mechanical,Crystallization and Foaming Properties of Poly(Lactic Acid)

Poly(lactic acid) (PLA)/talc composites containing different contents of talc were prepared by melt blending. Multiple properties of the prepared composites were investigated including mechanical, rheological and crystallization as well as foaming properties. Tensile test results indicated that the mechanical properties of the composite with 3% wt. talc showed significant reinforcement and toughening effect. When the talc content reached 10%, Young's modulus of the composite was increased by 35% compared with pure PLA. The morphological results showed that the talc layers were partially delaminated and uniformly dispersed in the PLA matrix at low loading. Differential scanning calorimetry (DSC) and polarized optical microscopy (POM) results indicated that 3% wt. talc significantly increased the crystallinity of the PLA matrix. The thermogravimetric analysis (TGA) results demonstrated that the thermal stability of PLA/talc composites was enhanced as well. Moreover, talc at low loading could act as a plasticizer in the polymer flow, which was investigated by rheological tests. The batch foaming experiments revealed that 3% wt. talc loading had the most notable heterogeneous nucleation effect, with the cell size decreasing from 15.4 μm for neat PLA to 8.5 μm and the cell density increasing by 298%.     

The Effect of Poly(Ethylene Succinate) on Mechanical Properties of PLLA/PES Blend Prepared by Melt-Blending

Fully biodegradable poly(L-lactide) and poly(ethylene succinate) (PLLA/PES) blends were prepared via melt-blending using PLLA and PES as reactants in a stainless steel chamber. The prepared PLLA/PES blend, as well as neat PLLA and PES, was characterized by Fourier transform infrared spectra (FTIR) and X-ray diffraction (XRD) to confirm the structure and the crystallization of PLLA in the blend. The mechanical properties of PLLA/PES blends were determined by bending and tensile tests and the effects of PES content on the mechanical properties of PLLA/PES blends were investigated. It was found that blending some amount of PES could significantly improve the elongation at break while still keeping considerably high strength and modulus. With increasing PES content, both strength and modulus gradually decreased; however the elongation at break significantly increased. SEM was used to examine the morphology of fracture surfaces of PLLA/PES blends.