超声毛细效应的探究

通过对超声波泵现象进行预实验,判断出毛细管内液面反常上升的高度与毛细管、液体和超声波的诸多性质相关.从挤压模效应和空化效应分别对超声毛细效应进行理论分析,判断出了影响超声波作用下毛细管内液面反常上升的因素,并通过实验测量结果验证了此理论的自洽性.     

利用光的反射原理讲解旋转液体抛物液面的焦距与转速的关系

本文利用几何光学的反射原理,以一种较为直观的方法对旋转液体抛物液面的焦距与转速之间的定量关系进行了理论推导,一定程度上为同学们深入理解该实验的基本原理提供了帮助。同时,在实验室现有的旋转液体综合实验仪的基础上,对旋转液体抛物液面焦距的测量方法进行了优化,并对不同转速条件下液体抛物液面的焦距进行了实验测量;同时利用拟合曲线图的形式,对旋转液体抛物液面焦距的实验测量值和理论计算值进行了比较,结果表明实验测量值和理论计算值具有很好的吻合性。     

基于NI myDAQ数据采集器的表面张力系数测量系统

基于NI myDAQ数据采集器、应变式力传感器和位移传感器,用LabVIEW设计和制作了拉脱法测液体表面张力系数的实验系统,该系统可完整定量地记录液面拉破前后液面高度和液体表面张力的变化过程,液面高度测量精度达到0.01mm,表面张力测量精度达到10-5 N.用该系统测量了水、乙醇及其混合液体的表面张力系数,发现随着乙醇体积分数的增加,表面张力系数呈非线性递减,且液膜可拉伸长度也非线性减小.     

低温液面自动控制器

本文介绍了一种液氮自动输液装置,它和已生产的低温液面计配合,用于液氮的自动输液和液面控制.输液管上的电磁阀用作液体开关.该仪器既可控制液面高度,也能同时测量液面高度.若仅用于控制液面,可与其它液面计配合使用.     

毛细管法测量液体黏度实验再设计

设计了简单的毛细管法测量液体黏度的实验装置,通过测量液面高度与时间的变化,拟合实验数据得到液体的黏度,省去了传统的恒压液槽的设计.通过毛细管外加恒温管的方法,可较准确地测量不同温度下液体黏度的变化.通过实验给出泊肃叶公式中液体流速与毛细管长度、内径以及两端压强差的关系.     

RL-1型旋转液体特性研究实验的改进方法

旋转液体特性研究实验是大学物理实验中典型的综合实验项目之一,本文通过进一步优化现有的RL-1型旋转液体实验仪的设计,解决了两种重力加速度测量方法中存在的旋转液面特征点高度测量不准和反射点位置判断不清的问题,较大地提高了测量精确度,达到了理想的实验效果。     

电容式传感元件测量导电液体的液面高度

阐述了用一根圆柱形电极测量导电液体液面高度的实验原理，方法，过程和实验结果，并说明了它对物理实验教学的意义。     

用光学方法测量液体的物理参数

实验发现,激光束照射在振动的液面上,表面波对入射光可产生衍射;插入液体里的金属细丝被拉出液面时,由于液体的润湿效应,其周围的液体拉伸一定高度而断裂。以上两种实验现象机理,可用于液体表面张力系数的测定。激光经小孔透射样品池中的液体介质,在液体上表面发生遮光效应,根据其机理,建立了一种测量液体折射率的新方法。     

气体压强改变对液体内部压强影响的定性实验验证

采用U形管压强计进行定性测量,验证了气体压强的改变对液体内部压强有着不可忽视的影响.在气压减小而液面上升的特殊情况下,实验得出的液体压强变化与利用液体平衡状态分析得出的结果一致.围绕此话开展研究性学习,可以加深学生对液体压强公式的理解.     

利用光杠杆测量流体压强及流速的微小变化

将流体压强及流速的微小变化转化为U形管或测压管液面高度的变化.又利用光杠杆放大原理,将液面高度难以判断的微小位移放大成激光光点明显的位移,从而实现了液体压强微小变化的测量.实验结果表明,光点的位移与压强变化线性度高,测量灵敏、结果可靠.     

Fragmentation instabilities of a drop as it falls in a miscible fluid

We review here a series of experiments on the fragmentation instabilities that a liquid drop undergoes as it falls inside a fluid with which it is miscible, so called the solvent. Motivated by the original experiments initiated by Thomson and Newall in 1885, we started to investigate this subject more than one decade ago, encountering up to date a number of challenging problems in hydrodynamical instabilities, complicated by the presence of transient interfaces between the drop and the solvent. In particular, we have shown that when a drop of liquid is deposited over the surface of the same liquid, it falls down inside the solvent because the energy associated to its surface tension against air is instantaneously converted into kinetic energy. As a consequence, a very fast fluid injection takes place as the drop touches the free surface of the solvent and the drop enters inside the solvent. Due to the hydrodynamical instabilities related to the large velocity gradients, it develops into a ring that expands radially. The ring continues to go downwards inside the solvent until it stops at a certain height due to viscous dissipation. In the first stages of the ring expansion, a fluid membrane remains attached to the ring, so-called “turban" for its shape, which is concave or convex depending on the sign of the density difference between the drop and the solvent. When a small density difference is introduced between the drop and the solvent, the ring becomes unstable because of density gradients and it fragments into smaller droplets. On their turn, the secondary droplets may undergo the same instability and may fragment again, so that a cascade of fragmentation takes place. If the density difference is positive, that is, the drop is heavier than the solvent, the secondary droplets continue to go down deeper inside the solvent, until the whole process is washed out by the slow diffusion of the concentration gradients. When the density difference between the drop and the solvent is negative, then the secondary droplets rise up to the free surface of the solvent, where they are distorted by the equivalent of an impact with a rigid wall. Universal scaling laws for the cascade of fragmentation and for the dynamical behavior of the drop have been derived and accompany the experimental observations.     

液体表面张力系数测量装置的改进

对用力敏传感器测量液体表面张力系数仪器进行研究,重新设计了吊环,便于吊环的水平调节,对待侧液体表面均匀下降的方法和实验装置做了重新设计,减小了实验误差,同时增加了待测液体的变温控制,能够精确测量液体表面张力系数与温度的关系,扩充了实验内容.     

高精度检测球面面形的方法研究

短波光学的迅猛发展和高精密光学仪器的需求日益增多,对高精度表面的加工与检测也随之重要起来。而在一般的干涉检测中,球面镜检测精度主要依赖参考镜的精度。利用Jensen提出的干涉仪绝对校准理论可以去除参考镜的误差和干涉仪的附加波像差,从而提高被测件测量精度。在研究Jensen绝对校准理论的基础上,提出一种利用泽尼克(Zernike)多项式进行波面相位转换的方法进行波面处理,并提出具体实施方案。对面形精度优于A／37小凸球面进行测量得出了较好的结果,打破了标准镜头最优A／20的局限,使这一理论简单易行地赋予应用。从而实现了高精度检测球面面形。     

超声辅助磨削杯形砂轮变幅器设计与试验*

超声辅助磨削在硬脆材料的加工中应用广泛。为研制以杯形砂轮为加工工具的超声辅助磨削主轴附件式工具系统,建立了杯形砂轮变幅器的理论模型,推导了其频率方程,并通过Matlab开发了杯形砂轮变幅器设计软件。利用该软件结合有限元分析对杯形砂轮变幅器进行了设计。将研制的杯形砂轮变幅器与BT40刀柄一体化外套筒、导电滑环装配组成了杯形砂轮超声辅助磨削主轴附件式工具系统。对该超声振动系统进行了阻抗分析试验及超声谐振试验,结果表明,该超声振动系统阻抗性能较好,能够使杯形砂轮产生稳定的超声振动,验证了所提出的设计方法的正确性,为主轴附件式超声磨削装置的设计提供了理论参考。     

Faraday dosimetry characteristics of PIII doping processes

A Faraday cup dosimetry system was developed and characterized to address the issues of plasma immersion ion implantation (PIII) dose measurements. Pure ion current was measured by using an electrostatic suppression mechanism combined with high-bandwidth fiber-optic electronics to isolate high-voltage pulses and eliminate the primary and secondary electron and displacement currents. The ion-current waveform measured by the Faraday cup was verified by an XPDP1 particle-in-cell simulation. All of the positively charged ions striking the target surface were counted for implant dose by the Faraday cup so that both high-energy implant dose during the pulse and low-energy implant dose between pulses can be separately determined. The dose of the high-energy implant during pulses, which is more influential on the junction depth, can be measured with a fairly good accuracy, although the low-energy implant dose cannot be accurately measured due to more complicated surface effects. Compared with other dosimetry methods for PIII doping processes, the Faraday dosimetry technique offers better repeatability and controllability for PIII processes due to its direct, in-situ manner.     

Hydrodynamics of slip wedge and optimization of surface slip property

The hydrodynamic load support generated by a slip wedge of a slider bearing was studied. The surface slip property was optimized so that a maximum hydrodynamic load support could be obtained. A multi-linearity method was given for the slip control equation of two-dimensional (2-D) wall slip. We investigated 2-D wall slip and the hydrodynamics of a finite length bearing with any values of the surface limiting shear stress. It was found that the hydrodynamic effect of the slip wedge is greater than the traditional geometrical convergent-wedge. Even though the geo- metrical gap is a parallel or divergent sliding gap, the slip wedge still gives rise to a very big hydrodynamic pressure. The optimized slip wedge can give rise to a hy- drodynamic load support as high as 2.5 times of what the geometrical conver- gent-wedge can produce. Wall slip usually gives a small surface friction.     

不同吊环组合对液体表面张力系数测量的影响

使用FD-NST-Ⅰ型液体表面张力系数测定仪,通过更换细铜丝加大吊环、细铜丝加小吊环、细棉线加大吊环、细棉线加小吊环四种组合的吊环测量了不同温度下纯净水和95%酒精的表面张力系数。由实验结果分析得到在使用细棉线加大吊环组合时,表面张力系数的测量结果相对于其他三种组合有最小的百分误差。     

壁面涂层构型对垂直降膜流动特性的影响

利用特种表面涂层材料对实验管壁进行改性,使液膜形成沟流,实现液膜的内外表面溶液重新掺混;管外涂层的不同构型形成表面张力梯度表面,在吸收过程中可引导液滴向液膜方向运动,促进液膜扰动,从而达到强化传质的目的.通过液膜流动的可视化照片和液膜波动特性的实验结果,对不同状况下的流动形态进行初步分析.     

Probing the interaction of ionic liquids with graphene using surface‐enhanced Raman spectroscopy

We report an in situ measurement of the interaction of an imidazolium‐based room temperature ionic liquid with both pure silver and a graphene‐over‐silver electrode under an applied electrochemical potential. At a negative applied potential, overall signal intensity increased indicating enhanced ionic liquid concentration at both silver and graphene electrodes. Vibrational modes associated with the imidazolium ring exhibited greater intensity enhancements and larger peak shifts compared with the anion indicating that the cation adsorbs with the ring and alkyl chain parallel to the electrode surface for both silver and graphene. In contrast to the silver, the surface enhanced Raman spectra of the ionic liquid near graphene showed shifts in the cation peaks even at no applied potential because of the strong π–π interaction between the ionic liquid and the graphene. Furthermore, the intensity of the graphene peak decreased in the presence of ionic liquid possibly due to the interaction between the ionic liquid and graphene. These results illustrate the effectiveness of surface‐enhanced Raman spectroscopy to investigate electrolyte interactions with graphene at the liquid/electrode interface. Copyright © 2015 John Wiley & Sons, Ltd.     

液体表面张力系数实验装置的改进

对现有吊环法液体表面张力系数测量仪的水平调节装置、吊环升降装置存在的不足进行了改进,在原有仪器上增加了液体加热装置,以便对不同温度下的液体表面张力系数进行测量,实验说明新的实验装置更加科学合理.通过实验对比得出:新的实验装置操作方便、实验误差小、重复性好,有推广价值.