空气的浮力与不连续性对密立根油滴实验测量值影响的定量分析

密立根油滴实验通过测定带电油滴所带的电荷量来测定基本电荷的电荷量,并验证电荷的量子化效应.为了实验的方便,一些常用实验方法中将油滴所受空气浮力忽略,甚至忽略空气的不连续性对空气粘滞系数的影响,导致了测量结果的系统误差.基于静态法,定量讨论空气浮力及其不连续性对油滴电荷量测量结果的影响,发现忽略空气浮力所产生的相对误差不超过0.1%,而忽略空气的不连续性所产生的相对误差可以超过15%.因此,在实验中必须考虑空气的不连续性对空气的粘滞系数的影响,从而提高油滴带电荷量测量的精度.     

用数码照相法研究落球法测量液体的粘滞系数实验

本文用数码照相法研究落球法测量液体的粘滞系数实验,用截图软件对照片进行下落距离的测量．分析了数码相机作为时间测量仪器的使用,以及实验结果所能达到的测量精度．     

计算机编程在密立根油滴实验中的应用简

用直线函数拟合了环境温度与空气粘滞系数的关系,并利用VisualBasic编写了密立根油滴实验的数据处理程序,提高了计算油滴带电量的准确性。利用VisualBasic程序的可视化界面形式体现,简化了数据处理过程。利用Origin软件对实验数据进行处理,直观显示了平衡电压、下落时间与油滴所带电荷数的关系。     

计算机编程在密立根油滴实验中的应用

用直线函数拟合了环境温度与空气粘滞系数的关系,并利用Visual Basic编写了密立根油滴实验的数据处理程序,提高了计算油滴带电量的准确性。利用Visual Basic程序的可视化界面形式体现,简化了数据处理过程。利用Origin软件对实验数据进行处理,直观显示了平衡电压、下落时间与油滴所带电荷数的关系。     

密立根油滴实验中的布朗运动

在进行密立根油滴实验时,如果选择的油滴过小,油滴会有明显的布朗运动,造成测得的下落时间与理想下落时间存在偏差.本文对密立根油滴实验中油滴的下落问题进行了实验观察和理论研究,并基于朗之万理论,求解了描述油滴运动的随机微分方程.通过引入单次下落时间偏差和多次下落时间偏差分别考察了油滴布朗运动的剧烈程度以及布朗运动对油滴下落时间的影响.结果表明,实验中由于实验次数有限,当油滴比较小时油滴的布朗运动对于实验的影响仍然需要考虑.     

无限广延法测量液体粘滞系数的实践研究

无限广延法测量液体的粘滞系数,关键是获取收尾时间t0。实验中释放小球时,无法严格确定小球沿圆筒的中心轴线下落,往往会产生较大的实验误差。因此在实验中对3#管,4#管,5#管,具体研究了偏移中心轴线下落给实验带来的具体影响,发现小球在管中的下落时间随着偏移中心轴线距离的增加而减小。     

在测液体粘滞系数实验中记时起点的确定

在液体粘滞系数测定实验中(用斯托克斯法),记时起点的确定是十分重要的。因为在这个实验中,通过误差分析,我们知道,小球下落的时间t,小球下落的距离L,是对总误差影响最大的两个因素。为提高测量精度,除提高计时技术,增加时间t的测量次数外,还需要尽量增加时间t,用来减少η/ t。同时,也     

利用Scratch软件实现落球法测量液体粘滞系数实验的仿真

利用Scratch软件实现了对"落球法测量液体粘滞系数"实验的演示与仿真,对实验中小球从静止下落过渡到匀速运动状态这一较复杂的微小变化过程进行了完整演示,同时给出了小球运动速度、位移随时间变化的图像,加深了学生对实验内容的理解。     

液体粘滞系数测量方法的改进

落球法是测量液体粘滞系数的最简单直接的方法，但小球的下落时间难以精确测定，本提出了用光电法来测定小球的下落时间，可以较大幅度地提高测量结果的精度。     

用落球法测量η实验中小球下落速度的辨析

用落球法测量η实验中小球下落速度的辨析张兆钧（西安交通大学物理系７１００４９）测量液体的粘滞系数有多种方法，落球法是其中一种．它适用于粘度较大，有一定透明度的液体，这种方法需要测量小球在盛有液体的圆管内匀速铅直下落时的速度．由于小球在下落运动时，受到...     

A theory of localized electronic breakdown in insulating films

A review of measured breakdown properties in insulating films and of electronic theories of breakdown shows both theoretical and experimental inconsistencies. A theory is proposed in which electronic breakdown is caused by local chance events, such as a succession of avalanches at one spot. Successive avalanches sustain the growth of space charges, the local cathode field, and the avalanche rate. When the cathode field becomes large enough to make continuation of avalanching a certainty, instability with current runaway arises, causing breakdown. According to theory, breakdowns occur over a range of fields, their chance increasing very strongly with field; the breakdowns occur randomly in space and in time; the time to instability on a breakdown event decreases as some exponential function of increasing field; the breakdown field can both increase and decrease with temperature; it may be electrode dependent, and it decreases first rapidly and then more slowly with increasing film thickness. Observations made in a number of insulating films support the proposed theory.     

聚乙烯薄膜中空间电荷短路放电复合率的发光法研究

通过对在直流高压作用下低密度聚乙烯薄膜中注入的空间电荷的短路放电发光测量,研究了聚乙烯薄膜中空间电荷的复合率.通过短路放电光子数的测量及定量分析考察了电压极性、场强大小及加压时间对短路下电荷复合率的影响.结果表明发光强度（复合率）随外加场强的变化明显,而与加压时间的关系不显著.但场强高于80 MV/m时发光强度（复合率）的增大速度变慢.结合本实验结果及他人的相关数据,得出了聚乙烯薄膜样品的发光效率约为5.9×10^-6,短路初始阶段的0.2 s内样品的电荷复合率约为2.8%. 关键词： 空间电荷 短路放电 复合发光 复合率     

A Rheological Study of Xanthan Polymer for Enhanced Oil Recovery

This study explored the potential application of xanthan gum as a polymer-flooding agent for oil recovery applications in a specific Devonian oil field. Rheological measurements using oscillatory and steady shear were carried out to examine the change in shear viscosity when the polymer was applied under reservoir conditions. The xanthan rheological properties were described by the Herschel–Bulkley and Ostwald models to characterize its non-Newtonian behavior. As expected, the results showed that higher xanthan concentrations raised the polymer viscosity and increased the degree of shear thinning. Addition of alkalis caused the viscosity of the xanthan solutions to decrease, but they maintained their shear-thinning properties. Polymer solutions in typical oil field brine increased in viscosity by ca. 400% for 720 hours storage time. On the other hand, as expected, the solutions lost their viscosity gradually with increasing temperature. However, at reservoir temperature (68°C), the polymer solutions kept more than 60% of their initial viscosity. In oscillatory deformation tests it was observed that all the measured viscoelastic properties were influenced by temperature and confirmed that xanthan solution behaved as a weak-gel. An order-disorder transition exists within the xanthan-brine solutions which responds to changes in solution concentration, temperature and alkalis.     

稠油储层核磁共振孔隙度校正方法

受原油粘度的影响,利用核磁共振（NMR）测井获取的稠油储层的测井NMR孔隙度远低于地层的真实孔隙度,给稠油储层评价和NMR测井技术的应用带来极大挑战.为提高稠油储层孔隙度计算精度,必须对测井NMR孔隙度进行稠油校正.本研究选取我国南海东部盆地某油田韩江组10块代表性岩心样品,分别开展了原始状态、饱含稠油、残余油和饱含水状态的NMR实验.研究了孔隙含油相对体积对岩心NMR孔隙度的影响,并建立了基于地层深测向电阻率分类的岩心NMR孔隙度校正模型.将基于实验结果建立的岩心NMR孔隙度校正模型推广到实际地层,对目标区域A14井稠油储层实测测井NMR孔隙度进行处理的结果表明：本文提出的方法能够有效地校正孔隙含稠油对实测测井NMR孔隙度的影响,得到地层的真实孔隙度;校正前、后的稠油储层测井NMR孔隙度与常规气驱法测量的岩心孔隙度之间的相对误差由11.19%降低到4.84%.     

On the influence of viscosity on the characteristic time of the instability of a charged drop

A nonlinear integral equation describing the evolution of spheroidal deformation of a drop that is unstable with respect to its intrinsic charge is derived and solved for arbitrary values of viscosity. It was shown that, due to an essentially nonlinear character of the phenomenon, the characteristic time of instability develop-ment equals the time of tenfold increase in the amplitude of an initial, physically infinitesimal spheroidal deformation of an unstable drop. The dependence of the instability characteristic time on the drop viscosity is described by an increasing linear function.     

聚合物驱两相流试井参数敏感性

考虑油水两相、生产历史、油藏平面非均质性、井筒储存和表皮效应等因素,建立了生产历史阶段聚合物驱数学模型和不稳定试井阶段的流线模型,用流管法对解释模型进行了数值求解.研究表明:随着油水粘度比的增大,压力及压力导数曲线向上平移,随着生产时间的增加,储层的有效渗透率降低,当高渗透条带沿主流线方向分布时,注水井压降导数曲线反映不出油水前缘的影响,而随着聚合物注入浓度的增大,压力导数曲线下凹出现的越来越早.     

考虑动半径和粘度变化的稠油非牛顿不稳定渗流数学模型

针对稠油非牛顿特征,在Bingham流体渗流方程基础上,通过对动半径和粘度进行表征,建立同时考虑启动压力梯度、动半径变化和粘度变化的非牛顿稠油不稳定渗流数学模型,完善Bingham型稠油渗流数学模型.通过空间、时间离散差分及Matlab数值计算,得到非牛顿稠油非稳态渗流地层压力分布.结果表明,相同产量下,随启动压力梯度增大,动半径向井方向移动;启动压力梯度越大,压降曲线越陡,相应近井压降越大;相同启动压力梯度下,产量越大,不同吞吐周期压力差距越大.将半径和粘度动态变化相结合,弥补了现行非牛顿稠油渗流数学模型的-个缺陷.     

Physical processes upon the optical discharge propagation in optical fiber

Recent theoretical works on the physics of the fiber fuse effect in optical fiber are reviewed. A qualitative interpretation of the significant increase in the absorption of quartz glass with increasing temperature is presented. The results of the 2D simulation of the optical discharge propagation in optical fiber are analyzed. The results of the simulation are in agreement with the recent measurements of the spatial distribution of the bright-spot radiation intensity. It is demonstrated that the recently demonstrated fast propagation of the optical discharge can be interpreted as light detonation. A mechanism for the formation of a chain of cavities in the fiber-fuse track is considered. It is demonstrated that this effect cannot be interpreted using the Rayleigh capillary instability due to the relatively high viscosity of glass. The periodicity of the cavities can be related to an instability of a new type. A high-density double layer of charges emerges at the plasma-liquid interface. A tendency towards an increase in the surface owing to the repulsion of like charges provides for a development of the instability that causes the formation of the chain of cavities.     

纳米TiO2颗粒对电流变悬浮液中硅油的挥发增强效应

物理化学性能稳定的二甲基硅油常作为电流变液分散相, 当与纳米量级的介电颗粒混合组成电流变悬浮液时, 在非密闭环境下极易挥发, 时间足够长时, 可完全挥发. 本文通过实验研究了纳米二氧化钛颗粒对二氧化钛和硅油组成的悬浮液中硅油挥发增强现象, 分析表明, 纳米颗粒在电流变悬浮液的硅油气-液界面上形成纳米尺度的凸型曲面, 使液面上蒸气压大大提高, 导致挥发增强. 本文还对颗粒浓度, 环境温度和硅油黏度等对硅油挥发增强效应的影响进行了系统的研究和分析.     

高压下Zn2GeO4带隙变化的第一性原理研究

采用基于密度泛函理论的第一性原理计算研究了Zn₂GeO₄晶体在高压下的电子结构和带隙变化行为. 研究结果发现, 随着压强的增加, Zn₂GeO₄ 能带间隙先变大, 在压强为9.7 GPa时达到最大值, 然后减小. 通过电子态密度、电荷布居数和电子差分密度分布图的研究分析可知:在低压区域(0< P< 9.7 GPa), 带隙的变大主要是由于原子间距离的减小造成的共价性增强和Ge原子随压强的变大局域性增强引起的; 在高压区域(P>9.7 GPa), 则是出现了离域现象, 诱发了离域电子的产生, 从而使带隙减小.