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1.
研制了悬滴法液体表面张力测量系统,该系统包括图像采集系统、耐高压实验本体和温度控制系统等.悬滴图像信息由高分辨率的CMOS相机采集,并利用Canny算法进行边缘检测,进而提取悬滴边界并进行坐标变换,以获取悬滴的轮廓坐标,采用坐标轮换法与Newton法结合实现悬滴边界的全轮廓拟合计算.实验系统的温度范围和温度波动度分别为:20~180℃,±0.01℃;压力范围为:0~20MPa.为了检验系统的可靠性和精确性,测量了正庚烷在温度范围为293.15~373.15K的表面张力.通过不确定度分析,测量流体表/界面张力的相对不确定度为0.22%.  相似文献   

2.
"双悬线平衡法"测量地磁水平分量   总被引:2,自引:0,他引:2  
吴智  朱晔明  丁方圆 《大学物理》2005,24(1):59-61,63
采用“双悬线平衡法”,并利用外加可调磁场与地磁水平分量补偿的方法对地磁水平分量进行了测量.当磁针所受磁场力和双悬线扭力平衡时,以悬线扭力为零作为外加磁场与地磁水平分量“补偿”的判定依据,由于此时的外加磁场与地磁水平分量大小相等方向相反,从而测得地磁水平分量。  相似文献   

3.
悬线式物镜力矩器是目前光学头系统中使用最为广泛的力矩器,其动态特性直接决定了光学头的读写性能。基于ANSYS参数化设计语言(APDL)建立了悬线式光学头物镜力矩器的仿真设计平台。通过仿真平台进行了力矩器一阶共振频率和峰值、二阶共振频率和峰值、扭转共振频率、静态灵敏度、动态灵敏度和相位等动态特性参数的仿真实验,仿真计算的结果与实际测量的结果相比,最大相对误差为4.2%。该仿真平台对于二维乃至三维悬线式物镜力矩器的设计和评价都具有重要的指导意义。  相似文献   

4.
在验证机械能守恒定律实验中,针对小球经过光电门时瞬时速度的测量不准确的问题,提出了两点改进的方法:考虑到光束的有效宽度,建议将瞬时速度公式进行修正;另外调节光束垂直照在小球的悬线上.这两种改进方法能够使验证机械能守恒定律实验更加准确.  相似文献   

5.
利用LabVIEW测量了杆的频率响应曲线,确认存在2个相近甚至几乎重叠的共振峰.通过拟合理论曲线,比较精确地定出了2个共振频率以及相应的宽度,还研究了悬挂位置以及悬线对共振频率的影响.  相似文献   

6.
以求铜棒的动态杨氏模量的传统实验方法为基础,改变实验中悬丝的材质,使用轻质细铜丝作为悬线,研究在新悬线吊挂下试样粗铜棒和试样细铜棒在不同悬挂位置对应的共振频率,用求平均值的方法求出节点处的共振频率,并求出铜棒的杨氏模量,误差较小,验证了使用细铜丝悬线这种实验方法的可行性。  相似文献   

7.
飞秒径向偏振光紧聚焦实验   总被引:1,自引:0,他引:1  
以飞秒激光器为光源,搭建记录测量聚焦光斑的光学实验系统,研究飞秒径向偏振光紧聚焦特性.数值模拟表明当物镜数值孔径为0.9,波长为750 nm时,线偏振光和径向偏振光焦斑的最小半高全宽分别是1.3 μm和1.0 μm.实验中,使用全息干板作为记录介质,记录和测量微小的聚焦光斑,并通过精密电动平移台实现几十纳米量级步长的移动,获得精确焦平面处的聚焦光斑.测量结果表明,线偏振光和径向偏振光焦斑的最小半高全宽分别是4.6 μm和2.9 μm.在高数值孔径聚焦条件下,径向偏振光可以获得比线偏振光更细锐的聚焦光斑.  相似文献   

8.
在转动惯量实验中设计了反射式激光计时器,在不改变悬盘形状与质量分布的前提下,采用非接触式测量,可以更准确地测量摆盘的摆动周期.  相似文献   

9.
分析了用悬线将一重球悬挂于天花板下,然后拉重球下方的另一悬线,此后两根悬线谁先断裂这一典型力学问题.结果表明,当拉动悬线的速度v小于某一临界速度Vc时,球上方悬线先断裂;当v>Vc时,则情况较为复杂,具体是上方悬线断裂还是下方悬线断裂取决于悬线能承受的极限张力Fm;当v>>Vc时,选取具有合适的Fm值的悬线,可使得球下方的悬线先断裂.  相似文献   

10.
在分光计实验教学过程中,在完成自准法测量三棱镜的顶角的基础上,让学生把实验中能够清晰观察到的汞灯棱镜光谱中不同波长谱线对应的折射率利用最小偏向角法进行测量,再利用正常色散的柯西经验公式对数据进行拟合,作出n-λ曲线并求出所用材料(三棱镜)的系数A、B、C。通过上述实验内容的拓展,不仅让学生进一步熟悉了最小偏向角法测量三棱镜玻璃折射率的实验操作方法,而且让学生对棱镜玻璃波长色散的物理含义有了定量上的深入理解。  相似文献   

11.
An efficient method for nonlinear vibration analysis of mistuned centrifugal impellers with crack damages is presented. The main objective is to investigate the effects of mistuning and cracks on the vibration features of centrifugal impellers and to explore effective techniques for crack detection. Firstly, in order to reduce the input information needed for component mode synthesis (CMS), the whole model of an impeller is obtained by rotation transformation based on the finite element model of a sector model. Then, a hybrid-interface method of CMS is employed to generate a reduced-order model (ROM) for the cracked impeller. The degrees of freedom on the crack surfaces are retained in the ROM to simulate the crack breathing effects. A novel approach for computing the inversion of large sparse matrix is proposed to save memory space during model order reduction by partitioning the matrix into many smaller blocks. Moreover, to investigate the effects of mistuning and cracks on the resonant frequencies, the bilinear frequency approximation is used to estimate the resonant frequencies of the mistuned impeller with a crack. Additionally, statistical analysis is performed using the Monte Carlo simulation to study the statistical characteristics of the resonant frequencies versus crack length at different mistuning levels. The results show that the most significant effect of mistuning and cracks on the vibration response is the shift and split of the two resonant frequencies with the same nodal diameters. Finally, potential quantitative indicators for detection of crack of centrifugal impellers are discussed.  相似文献   

12.
王刚  邵丽晖  刘耀宗  温激鸿 《中国物理》2006,15(8):1843-1848
Based on a better understanding of the lattice vibration modes, two simple spring--mass models are constructed in order to evaluate the frequencies on both the lower and upper edges of the lowest locally resonant band gaps of the ternary locally resonant phononic crystals. The parameters of the models are given in a reasonable way based on the physical insight into the band gap mechanism. Both the lumped-mass methods and our models are used in the study of the influences of structural and the material parameters on frequencies on both edges of the lowest gaps in the ternary locally resonant phononic crystals. The analytical evaluations with our models and the theoretical predictions with the lumped-mass method are in good agreement with each other. The newly proposed heuristic models are helpful for a better understanding of the locally resonant band gap mechanism, as well as more accurate evaluation of the band edge frequencies.  相似文献   

13.
为了更高效地测量声波谐振管的谐振频率,本文基于LabVIEW设计了测量声波谐振管谐振频率的扫频程序,分别得到了两端闭管条件下不同管长的谐振频率,以及首端闭管与尾端闭管条件下的谐振频率.此外,还通过绘制管内驻波波形图对声压波腹发生偏离的假设进行了验证.最后,对谐振管管身小孔开闭对谐振频率的影响进行了探究,发现小孔位置越接近驻波的声压波腹,谐振频率的偏离量越大.  相似文献   

14.
孔径旋转频闪散斑照相法测量物体的固有频率   总被引:2,自引:1,他引:1  
陈炳泉 《光学学报》2002,22(11):358-1361
提出了一种测量物体固有频率的新方法--孔径旋转频闪散斑照相法。该方法能方便地测量振动物体的固有频率,具有精度高、全场显示、条纹可见度好等优点,给出了理论分析和实验结果。  相似文献   

15.
秦波  陈久久  程建春 《中国物理》2005,14(12):2522-2528
Three kinds of resonant modes of a single layered circular elastic cylinder embedded in the elastic medium are analysed by considering the oscillation of the scatter's core, based on the fact that the core moves as a rigid body when the shell material is very compliant. The resonant frequencies of the single resonator acquired by our method are in good agreement with those calculated by the local interaction simulation approach (LISA) for the local resonant phononic crystal. Therefore, the local resonant characteristics of a single layered circular elastic cylinder can be used to evaluate the resonant frequencies of the phononic crystal. The effects of the geometrical and physical parameters of the shell and the core are also studied in details. This work is significant for designing the locally resonant phononic crystal based on the local resonant characteristics of the single resonator, and the resonant frequencies can be tuned by selecting the geometrical sizes and the materials.  相似文献   

16.
张强  周胜  励强华  王选章  付淑芳 《物理学报》2012,61(15):157501-157501
基于传递矩阵方法和光局域化原理, 本文研究了一维反铁磁光子晶体共振频率附近光学双稳态效应随电磁波入射角、 外磁场强度及电介质层数的变化.研究发现, 当外磁场为1.0 kG(1 G=10-4 T)、电磁波小角度入射时, 反铁磁材料高低共振频率附近均可探测到光学双稳态效应; 当电磁波大角度入射时, 仅在高共振频率附近探测到光学双稳态效应. 然而, 当外磁场强度增加到2.0 kG时, 由于反铁磁材料的高低共振频率向两侧移动, 低共振频率附近缺失的光学双稳态频率窗口又被有效激发. 此外, 电磁波小角度入射时, 电介质层数在低共振频率附近对双稳态效应影响较明显.  相似文献   

17.
冯鑫  何新霞 《应用声学》2016,24(1):33-33
海洋立管作为海洋油气开发的关键设备,在运行期间面临疲劳失效的风险,需要对立管进行疲劳试验。针对海洋立管共振弯曲疲劳试验法,提出基于 S7-300 PLC实现海洋立管共振弯曲疲劳试验装置控制系统的设计思想。采用黄金分割法,寻找确定试件共振频率点;同时,为保障系统能够在该共振频率点稳定运行,采用S7-300 PLC作为核心控制器,结合参数自调节模糊PID控制算法,设计完成疲劳试验装置中转速模糊PID控制器,实现对系统转速的精确控制,使得海洋立管疲劳试验装置控制系统在具有PLC控制灵活、可靠性高等特点的同时,大大提高了其自动化程度。  相似文献   

18.
Resonant spectra of 180° domain-wall oscillations in isolated magnetic bubbles are obtained with swept rf sinusoidal excitation and magnetooptic detection. The resonant frequencies are found to depend on the domain wall state. A quantitative micromagnetic theory involving contributions to the wall mass from already-present vertical Bloch lines with and without Bloch points explains the resonant frequencies, including their field dependence, and relates them to the wall states. It is found that for small in-plane fields, Bloch lines provide most of the effective wall mass. Moreover, if a Bloch point is present on a Bloch line, it tends to decrease the Bloch-line mass contribution.  相似文献   

19.
The resonant transmission of a small annular aperture, with a diameter much smaller than the radiation wavelength, in a thin metal plate is studied at microwave frequencies. It transpires that such an annular aperture supports several resonant guided modes, including those that are not quantized in the azimuthal direction. Such modes have resonant frequencies that are largely independent of the diameter of the annular aperture, thus being supported by annular apertures that tend to zero radius. The transmittance of such a structure at microwave frequencies is detailed and compared with the predictions of a finite element method model.  相似文献   

20.
Pairs of unequal strength, counter-rotating vortices were produced in order to examine the inception, dynamics, and acoustic emission of cavitation bubbles in rapidly stretching vortices. The acoustic signatures of these cavitation bubbles were characterized during their inception, growth, and collapse. Growing and collapsing bubbles often produced a sharp, broadband, pop sound. The spectrum of these bubbles, and the peak resonant frequency can generally be related to quiescent flow bubble dynamics and corresponding resonant frequencies. However, some elongated cavitation bubbles produced a short tonal burst, or chirp, with frequencies on the order of a few kilohertz. Theses frequencies are too low to be related to resonant frequencies of a bubble in a quiescent flow. Instead, the frequency content of the acoustic signal during bubble inception and growth is related to the volumetric oscillations of the bubble while it interacted with vortical flow that surrounds the bubble (i.e., the resonant frequency of the vortex-bubble system). A relationship was determined between the observed peak frequency of the oscillations, the highly stretched vortex properties, and the water nuclei content. It was found that different cavitation spectra could relate to different flow and fluid properties and therefore would not scale in the same manner.  相似文献   

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