双漏斗肥皂膜实验的研究

研究双漏斗肥皂膜实验中肥皂膜的形状、特性以及它随两漏斗距离的变化过程.从理论上导出并经实验验证一个重要结论:两漏斗口的最大距离等于其半径的1.325倍,然而这一点常常被忽视.     

肥皂泡破裂现象及产生小液滴分布研究

肥皂泡破裂产生液滴的大小和数目受破裂过程影响.本文研究了肥皂泡大小和高度对破裂产生液滴的影响,以及所产生液滴的分布规律.实验发现肥皂泡破裂产生的液滴在破裂高度较低时存在放射性线状分布现象;随着高度增加放射性线状分布消失;同时分析了肥皂泡破裂产生液滴的数目及肥皂膜的厚度随肥皂泡体积的变化规律.结果表明,肥皂泡体积和液滴数目之间存在幂函数关系,理想情况下肥皂膜厚度与碎片数目之间也存在幂函数关系.肥皂泡破裂过程中产生的液滴可以按照拟合结果大致分为小碎片,中等碎片和大碎片,它们分别对应于肥皂泡破裂过程的3个变化阶段.     

大小肥皂泡连通后的讨论与计算

从弯曲液面附加压强、气体状态方程以及"球缺"的有关公式等出发,对大小肥皂泡连通后的变化作了全面的阐释,导出了最后大泡半径的近似公式,还介绍了演示实验,拍得了3个泡的照片,测出了它们的半径,验证了这个近似公式.并对产生误差的原因作了分析.     

肥皂泡的光学和力学性质

从光学、力学、热学角度对肥皂泡的基本物理性质进行了实验研究,应用光学干涉原理实现对肥皂泡折射率及厚度较精确测量,并利用受力平衡原理求体积一定的肥皂泡的质量,再利用拉脱法测量肥皂液表面张力系数,进而研究肥皂泡表面自由能和内外压强差等.     

基于颜色仿真与匹配的肥皂膜厚度测量

肥皂膜在日常生活和物理学中经常会遇到.在薄膜干涉中也常会作为例子使用.人们总是关心,各种不同肥皂膜的厚度及其变化情况如何.本文以宽光谱LED为光源,观察并用相机拍摄了肥皂膜上的干涉图样,用颜色仿真和匹配法测量了肥皂膜的厚度.并且采用已知波长的单色光重复测量了肥皂膜厚度,同时用等厚干涉公式验证了测量结果.结果显示,与宽光谱光源相比,用单色光源做此类实验更具优势.     

用迈克耳孙干涉仪测肥皂膜厚度实验的分析

利用白光干涉原理,借助迈克耳孙干涉仪对肥皂膜的厚度进行了非接触测量.在干涉条纹宽窄相同的条件下,对不同层数的肥皂膜进行对比测量;在干涉条纹宽窄不同的条件下,对相同层数的肥皂膜进行对比测量;通过计算给出了膜的中心厚度和不确定度,对比分析了各种条件下测量时误差产生的原因.结果表明:单层、双层膜适合在宽条纹下测量,四层膜适合在窄条纹下测量.     

两连通气泡的平衡稳定性

针对气泡连通装置的平衡稳定性分析,引入"气泡坐标"概念,并采用最小能量法定量分析气泡初始状态对两连通气泡平衡稳定性的影响,准确解释了对此类问题的定性分析结果.同时,实验表明数值计算结果与实验测量结果之间误差极小,从而进一步验证了使用最小能量法分析气泡连通装置平衡稳定性的有效性与准确性.     

泡膜半径法测量液体表面张力

根据泡膜半径与液体表面张力系数所满足的函数关系进而测量液体表面张力系数,实验中利用U型管测量泡膜相对内压并通过电脑对泡膜的图像采集来测量泡膜半径,实验设计新颖独特,实验结果准确,且有利于提高学生的物理思维及对电子设备的使用能力。     

三级公自转行星系统中弯月透镜表面膜厚均匀性的研究

为提高弯月透镜表面的膜厚均匀性,对三级公自转行星系统中弯月透镜表面进行了膜厚均匀性的研究。构建了三级公自转行星盘的运动轨迹方程,并根据膜厚计算公式,建立了与三级盘倾角、公转半径有关的弯月透镜表面相对膜厚分布模型,采用电子束蒸发和离子束辅助沉积技术对分布模型进行了实验验证。此外,根据多次实验结果优化三级公自转行星系统结构参数,以提高弯月透镜表面的膜厚均匀性。实验结果表明,在未使用修正挡板技术的情况下,当公转半径为650 mm、倾角为60°时,可将弯月透镜凸面表面膜厚均匀性控制在±2.45%以内。     

《碰撞中的动量守恒》实验中一个易被疏忽的问题

高中物理学生实验《碰撞中的动量守恒》是用两个大小相同但质量不等的小球在斜槽末端发生水平方向上的正碰来验证动量守恒定律。实验巧妙地用小球在碰撞前后飞出的水平距离来代表碰撞前后的水平速度,从而把速度的测量简化为长度的测量。这是基于下述原理:做平抛运动的小球落到地     

Solvable Model for Electrolytic Soap Films: The Two-Dimensional Two-Component Plasma

We study a toy model for electrolytic soap films, the two-dimensional two-component plasma. This model is exactly solvable for a special value of the coulombic coupling constant q ²=2. This allows us to compute the disjoining pressure of a film and to study its stability. We found that the Coulomb interaction plays an important role in this stability. Also the adhesivity that measures the attraction of soap anions to the boundaries is very important. For large adhesivity the film is stable, whereas for small adhesivity a collapse could occur. We also study the density and correlations in the film. The charge density near the boundary shows a double layered profile. We show that the charge correlations verify a certain number of sum rules.     

高温超导飞轮储能系统磁悬浮力的仿真计算与实验分析

超导磁悬浮飞轮储能装置储能密度大、储能效率高,具有很好的发展前景。阐述了超导磁悬浮飞轮储能装置的基本原理。主要研究了超导块与永磁体之间的间隙、两者的半径和永磁体厚度等尺寸参数对磁悬浮力的影响。运用有限元分析软件ANSYS对磁悬浮的基本模型进行仿真计算,得到模型的磁力线分布,进一步总结各个参数和磁悬浮力之间的关系,并进行实验验证得到的结论。     

Analysis of time-of-flight distributions under pulsed laser ablation in vacuum based on the DSMC calculations

A theoretical study of the time-of-flight (TOF) distributions under pulsed laser ablation has been performed. 2D simulations of pulsed evaporation of atoms into vacuum on the base of the direct simulation Monte Carlo (DSMC) method have been carried out. It is found that for large evaporating spots (when the spot radius exceeds the initial plume length by a factor of five) the TOF distributions practically do not change with the spot radius variation. Moreover, it is shown that such distributions can be obtained from 1D calculations. Thus, in the frames of 1D approach, the TOF distribution is a function only of the number of the evaporated monolayers, but not of the spot radius. The shape of the TOF distribution is shown to strongly depend on the amount of the evaporated matter. Based on the calculated TOF distributions, dependence of the particle kinetic energy on the number of the evaporated monolayers has been obtained. To verify the theoretical results, experimental data on laser ablation of niobium and mercury have been used, which confirm the obtained dependences. The obtained results allow estimating the irradiated surface temperature from the TOF distributions for monatomic neutral gas.     

On the multiple-humped fission barriers and half-lives of actinides

The energy of actinide nuclei has been determined within a generalized liquid drop model taking into account the proximity energy, the mass and charge asymmetry, an accurate nuclear radius in adding the shell and pairing energies. Double and triple-humped potential barriers appear. The second maximum corresponds to the transition from compact and creviced one-body shapes to two touching ellipsoids. A third minimum and third peak appear in special asymmetric exit channels where one fragment is almost a magic nucleus with a quasi-spherical shape while the other one evolves from oblate to prolate shapes. The heights of the double and triple-humped fission barriers agree precisely with the experimental results in all the actinide region. The predicted half-lives follow the experimental data trend.     

强流离子束流聚焦状态的数值模拟

结合空间电荷透镜的原理图以及离子束流的磁流体运动方程对离子束流聚焦状态进行了理论研究。采用层流非碰撞模型数值计算了离子束流不同初始半径以及不同入射角的束流出射角、焦距以及最小焦斑半径。理论分析了能散度、色散像差等因素对束流最小焦斑半径的影响。在离子束流遵循能量和角动量守恒的原则下,对不同入射角度的离子束流的束流最大半径进行了模拟计算。研究表明,束流入射角度增大,会聚角和最小焦斑半径减小,焦距增大。束流半径增大,会聚角、焦距和最小焦斑半径都增大。最佳会聚角所在的平滑区域内束流的发散度以及能散度对最小焦斑半径的影响较大。束流发散度或者能散度的增加,都能导致最小焦斑半径的增大。入射角度绝对值相同的束流,束流最大半径相同。     

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The ion beam focused state is studied theoretically by combining the schematic of the charge lens in space and the magnetohydrodynamics equation of the ion beam. The theory applies laminar flow of non-collision model to calculate a series of parameters, such as the initial radius, the emergence angle, the focal length and the minimum radius of the focal spot. The effects of energy divergence and dispersion differs on the minimum radius of the focal spot are analyzed theoretically. Finally, in line with the principles of the conservation of energy and angular momentum, the maximum radius of the beam in view of different incidence angles of the ion beam are calculates. The results show that with the increase of incident angle, the confluence angle and the minimum radius of the focal spot will reduce, and the focal length will increase. Besides, when beam radius increases, the parameters above will increase. The minimum focal spot radius, within the smooth area, is in close relationship to the energy divergence and the divergence. The larger energy divergence and the divergence become, the larger the focal length will be. Besides, beam divergence with the same incidence angle will show common character on the maximum radius.     

Speckle interferometric technique to assess soap films

An speckle interferometric technique to monitor the thinning process of vertical soap film before the film rupture is presented. The interferometric arrangement consists in a double aperture pupil optical system which images an input diffuser. In a first step, a reference specklegram is stored in the computer buffer memory. Afterwards, the soap film is located in front of one pupil aperture, an uniform displacement of the diffuser is produced and a new speckle pattern is stored. The soap film status is characterized in terms of the changes that this dynamic phase object introduces in the correlation fringes obtained by applying a FFT algorithm to the resulting summed specklegram. This procedure is done in real time as far as the soap film evolves in the successive status. It is experimentally demonstrated that the soap film during drawing acts as a variable wedge. The correlation fringes behavior becomes an important tool to establish the wedge shaped soap film angle and the thickness variations.     

Bubbles under stress

We present an experimental and theoretical investigation of a system composed of two soap bubbles strained between two parallel solid surfaces. The two-bubble cluster can be found in several configurations. The existence and stability of each of these states is studied as a function of the distance between the two facing surfaces. The change of this distance can induce a transition from one configuration to another; we observe that most transitions are subcritical, showing that the system is often trapped in states where the minimum of free energy is only local. The hysteretic transitions are responsible for the dissipation of elastic energy. The existence of more than one stable states for given boundaries conditions combined with the absence of thermalization means that the history of the system has to be taken into account and that there is no unique stress-strain relation. In the present system, because of its simplicity, a complete quantitative analysis of these general processes is obtained. The presented results may contribute to a better understanding of the dynamics of more complex systems such as foams or granular materials where similar processes are at work.     

Visualization of two-dimensional flows by a Liquid (Soap) Film Tunnel

Experimentally produced two-dimensional flows have become possible in recent years due to the invention of Liquid Film Tunnel (LFT) in 1987 by Gharib and Derango. This simple, inexpensive, yet powerful device, which we have improved extensively over the last decade, can generate a variety of flows. Liquid (soap) films can be visualized through light interference effects produced by small variations in the film thickness. Flow-disturbing objects such as cylinders, wedges, and air bubbles create these variations. Monochromatic visualization of these thickness variations will render phenomenally accurate graphic information about the flow patterns thus produced. Under a polychromatic light, these interference effects can be spectacular, due to reflection of different colors by different isothickness regions.