Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction,and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investigation also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hydrodynamic parameters and the physical properties.

Growth and aggregation micromorphology of natural gas hydrate particles near gas-liquid interface under stirring condition

To investigate the morphological evolution of the whole growth and aggregation processes of hydrate crystals near the gas–liquid interface,we used a high-pressure visual reactor with high-speed camera to capture the micromorphology of hydrate particles in a natural gas+pure water system with pressure from 2.6 to 3.6 MPa and sub-cooling from 4.7 to 6.23C.The results showed that under low sub-cooling conditions,the amount and size of particles increased first and then decreased in the range of 0–330 lm,and the small particles always dominated.These particles can be roughly classified into two categories:planar flake particles and polyhedral solid particles.Then,the concept of maximum growth dominant particle size was proposed to distinguish the morphological boundary of growth and aggregation.In addition,the micro model was established to better reflect the effects of particle formation process and evolution mechanism near the gas–liquid interface under stirring condition.The results of this study can provide a guidance for flow assurance in multiphase pipeline.

Measurement of Liquid Concentration Fields Near Interface with Cocurrent Gas-Liquid Flow Absorption Using Holographic Interferometry

Real-time laser holographic interferometry was applied to measure liquid concentrations of CO2 in the vicinity of gas-liquid free interface under the conditions of cocurrent gas-liquid flow for absorption of CO2 by ethanol. The influences of the Reynolds number on the measurable interface concentration and on the film thickness were discussed. The results show that CO2 concentration decreases exponentially along the mass transfer direction, and the concentration gradient increases as Reynolds number of either liquid or gas increases. CO2 concentrations fluctuate slightly along the direction of flow; on the whole, there is an increase in CO2 concentration. The investiga- tion also demonstrated that film thickness decreases with the increase of Reynolds number of either of the two phases. Sherwood number representing the mass transfer coefficient was finally correlated as a function of the hy- drodynamic parameters and the physical properties.

Adsorption structures of frothers at gas–liquid interface using DFT method

Density functional theory (DFT) simulation was performed to investigate the adsorption mechanisms between frothers and gas–liquid interface. In water phase, the polar head group of the frother molecule was connected with water molecules by hydrogen bonding, while the non-polar group showed that hydrophobic property and water molecules around it were repelled away. The adsorption of water molecules on single frother molecule suggests that the complexes of α-terpineol-7H2O, MIBC-7H2O and DF200-13H2O reach their stable structure. The hydration shell affects both the polar head group and the non-polar group. The liquid film drainage rate of DF200 is the lowest, while α-terpineol and MIBC are almost the same. The adsorption layer of frother molecules adsorbed at the gas-liquid interface reveals that the α-terpineol molecules are more neatly arranged and better distributed. The DF200 molecules are arranged much more loosely than MIBC molecules. These results suggest that the α-terpineol molecule layer could better block the diffusion of gas through the liquid film than DF200 and MIBC. The simulation results indicate that the foam stability of α-terpineol is the best, followed by DF200 and MIBC.

Effect of current density on distribution coefficient of solute at solid-liquid interface

When current passes through the solid-liquid interface, the growth rate of crystal, solid-liquid interface energy and radius of curvature at dendritic tip will change. Based on this fact, the theoretical relation between the distribution of solute at solid-liquid interface and current density was established, and the effect of current on the distribution coefficient of solute through effecting the rate of crystal growth, the solid-liquid interface energy and the radius of curvature at the dendritic tip was discussed. The results show that as the current density increases, the distribution coefficient of solute tends to rise in a whole, and when the former is larger than about 400 A/cm 2, the latter varies significantly.

Curvature effects on electric-double-layer capacitance

Understanding the microscopic structure and thermodynamic properties of electrode/electrolyte interfaces is central to the rational design of electric-double-layer capacitors(EDLCs).Whereas practical applications often entail electrodes with complicated pore structures,theoretical studies are mostly restricted to EDLCs of simple geometry such as planar or slit pores ignoring the curvature effects of the electrode surface.Significant gaps exist regarding the EDLC performance and the interfacial structure.Herein the classical density functional theory(CDFT)is used to study the capacitance and interfacial behavior of spherical electric double layers within a coarse-grained model.The capacitive performance is associated with electrode curvature,surface potential,and electrolyte concentration and can be correlated with a regression-tree(RT)model.The combination of CDFT with machine-learning methods provides a promising quantitative framework useful for the computational screening of porous electrodes and novel electrolytes.

The Mechanism of Interfacial Mass Transfer in Gas Absorption Process

Based on the method of molecular thermodynamics, the mass transfer mechanism at gas-liquid interface is studied theoretically, and a new mathematical model is proposed. Using laser holographic interference technique, the hydrodynamics and mass transfer characteristics of CO2 absorption are measured. It is shown that the calculated results are in good agreement with the experimental data.

钢-混组合梁荷载-温度效应的统一解析模型

基于欧拉伯努利梁理论,提出非均布荷载、轴向力、梁端弯矩和非线性温度分布共同作用下的有滑移组合梁统一解析模型,推导组合梁挠度、界面剪力、滑移及截面应力的计算公式,开展简支组合梁和连续组合梁算例分析,讨论界面刚度和温度作用对界面滑移和挠度的影响.研究结果表明,组合梁温度作用产生的挠度与界面滑移由等效温度滑移应变和等效温度曲率决定,可以通过将桥面板与钢梁的温度分布各自分解为有效温度、竖向线性温差和残余温度等相互独立的3部分进行计算.简支梁和2跨连续梁算例在温度作用下的界面滑移沿梁长呈现反对称分布,滑移主要集中在距端部小于2 m的范围内,受滑移的影响,组合梁端部桥面板底面的拉应力水平较高,可以超过2 MPa,增加了底面混凝土开裂的风险.提出了温度作用下界面滑移组合梁的挠度影响系数,可以用于组合梁挠度的快速计算,其大小不仅与界面完全连接与界面无连接时组合梁的抗弯刚度比和组合效应系数有关,还受温度作用系数的直接影响.

硫酸钠盐渍土冻结温度计算模型构建及验证

土的冻结温度是使土体物理力学性质发生显著变化的关键温度,盐渍土中由于盐分存在使冻结温度的预测变得困难。本文提出了一种适用于硫酸盐渍土有盐分析出时的冻结温度计算模型,分别对硫酸钠自由溶液、硫酸钠盐渍土及石英砂的冻结温度变化规律展开了研究。首先,依据固液两相平衡时化学势的规律、冰晶表面曲率影响以及盐分结晶析出对溶液浓度的影响,构建了自由溶液、盐渍土及石英砂的冻结温度预测模型;然后,开展室内冻结试验得到了冻结温度测量值,通过计算测量值与计算值二者的均方根误差(RMSE)、显著性水平(α)及一致性系数(LA),验证了本文模型的精度与适用性。结果表明:土样中初始含水率越小,土样表面的毛细作用和吸附作用越强,使土样冻结温度越低。在土样孔隙中盐溶液有效浓度越大,冻结温度越小。由于盐分结晶的影响,有效浓度随盐浓度增大先增大后减小,然后保持不变。土样孔隙半径越小,冰晶表面曲率影响越大,冻结温度越低。该研究成果能为盐渍土盐冻胀变形及人工冻结中的温度参数分析提供一种新的方法。

Tracking the atomic pathways of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interface by in-situ liquid cell TEM

Using the in-situ liquid cell transmission electron microscopy, the three-stage growth of Pt3Ni-Ni(OH)2 core-shell structures at the gas-liquid interfaces was clearly observed, which consists of(1) a thermodynamically driven Pt3Ni alloy core by the monomer attachment,(2) a nickel(Ni) shell formation due to the depletion of the Pt salt precursor, and(3) the oxidation and of the Ni shell into Ni(OH)2 flakes. We also further observed the nucleation and growth of the Ni(OH)2 flakes on an existing layer either at the middle part or at the step edge. More interestingly, the dynamic transformation among a Pt3Ni alloy, Ni clusters and Ni(OH)2 flakes was also imaged even at a high electron dose rate.

多晶硅定向凝固过程中固-液界面特性研究

通过真空感应熔炼炉以不同拉锭速率制备了多晶硅铸锭,通过对铸锭的金相组织及少子寿命随凝固高度的变化及径向分布的分析,研究了多晶硅定向凝固过程中的固-液界面特性。结果表明:少子寿命随生长高度的增加先增加后减少,其径向分布与固-液界面相对应。由少子寿命分布图可以看出,固-液界面的曲率随拉锭速率的减小而减小,固-液界面形貌为胞状界面。计算分析表明,胞状的固-液界面造成Fe杂质的有效分凝系数增加了3个量级以上。

井内有流体时管柱弯曲临界力分析——封隔器管柱受力分析系统讨论之一

管柱弯曲临界力是判断井内管柱是否弯曲的重要依据 ,也是解决封隔器管柱受力分析中十分重要但又令人费解的“虚力”问题的关键。

界面曲率对超疏水微通道减阻的影响

针对具有横向微槽的超疏水微通道中的流动减阻特性,采用Fluent模拟了微通道中的二维层流流动,分析了气-液界面曲率、流动和结构参数对减阻效果的影响。结果表明:压降比和滑移长度随凸出角增大均呈单驼峰曲线变化;当θ=θ_(opt)时,随自由剪切面积比和周期单元长度增加,压降比和滑移长度均提高,减阻效果显著;当θ>θ_n,尤其是θ≈90°时,横向微槽起增阻作用,且提高自由剪切面积比和周期单元长度将显著降低压降比和滑移长度,增阻作用愈加显著;雷诺数对减阻效果影响很小。

力竭运动后大鼠皮层中Gray-I型突触形态的变化

通过力竭运动模型,对大鼠力竭后即刻、力竭后6、24h皮层内突触界面不同曲度类型进行了记数统计。结果表明:与对照实验动物比较,只有力竭后6h时突触界面曲度类型发生明显的变化。初步认为力竭运动可以影响到皮层突触形态结构。

视皮层LTP维持阶段的突触形态计量学研究

本实验使用１８～２０ｄ的幼年大鼠视皮层脑片标本，在ＬＴＰ出现后３ｈ取局部微脑片固定进行ＬＴＰ维持阶段超微结构的研究。分别与孵育相同时间而未予任何刺激的脑片和仅给予测试刺激的脑片作比较。运用图像分析仪分别对三组电镜结果进行以下参数的测量：（１）突触间隙的宽度；（２）突触后致密物（ＰＳＤ）的厚度；（３）活性区的长度；和（４）突触界面曲率。用双盲法对突触数目进行计量，并用立体计量学方法对各种突触类型进行定量，所得数据用方差分析进行统计学处理。结果显示：（１）ＬＴＰ形成后１５ｈ左右，其反应达到峰值，然后维持在最高水平一直到３ｈ仍无下降趋势；（２）突触间隙的宽度较两个对照组明显增宽；（３）ＰＳＤ的厚度也明显增厚；（４）活性区的面密度及突触界面曲率明显增加；（５）总突触数目和棘突触数目的数密度较空白对照明显增高；（６）穿孔性突触的数密度与对照组相比明显增加。结果提示：活性区面密度的增加及突触界面曲率的增大可能是ＬＴＰ维持的形态学基础。穿孔性突触的形成与ＬＴＰ的维持密切相关。

视皮层LTP形成后的突触形态特征

本文对产生ＬＴＰ的幼年大鼠视皮层脑片标本进行了电镜观察。研究发现，产生ＬＴＰ的实验组标本中有大的“Ｕ”形突触形成。这种Ｕ型突触的界面曲率可大于２，多有两个以上的活性区。活性区部位的曲率变化更为明显。而对照组未见到这种变化。提示Ｕ型突触可能是ＬＴＰ发生的结构基础。

加载面曲率对柔性压磁材料薄片力学性能的影响

在曲率较大的柱形或球形凸、凹接触界面之间的压力测量过程中,一般会将测试前呈平直薄片的柔性传感器敏感元压至与被测表面面型一致,这样就会因敏感元自身面型变化而引入测量误差。这是这类接触界面压力测量传感器研制中必须关注的问题。针对这一背景,以圆柱形接触界面为例,采用作者以前建立的含柔性泡沫元件组合结构的近似数值分析方法,建立凸圆柱面-柔性压磁材料薄片-凹圆柱面的有限元模型,通过数值模拟和相应实验,得到了不同曲率圆柱面加载下柔性压磁敏感材料薄片所受轴向压缩应力与轴向压缩应变之间的关系。结果表明,加载面曲率越小,应力-应变曲线的近似线性段的斜率就越大,在加载面曲率半径大于20 mm时,其影响基本可以忽略。该结果对于将柔性压磁敏感材料薄片作为敏感元开发大曲率柱形或球形接触界面之间的压力测量传感器具有理论指导意义。

幼年大鼠视皮层脑片标本LTP形成后的电镜观察

选取电生理实验中出现较大ＬＴＰ的脑片标本即时固定、切片、电镜观察。发现凹型突触增多，特别是有Ｕ型突触的形成，使突触界面曲率明显增大。本文就突触曲率变化与ＬＴＰ的关系进行了讨论。

复乳液在延展流中流变行为研究

为了探究复乳液内部子液滴的大小和位置分布对其流变行为的影响,采用二维波谱边界元素法数值模拟了延展流中同心复乳液和非对称复乳液的流变行为.通过改变子液滴的大小和位置得到复乳液不同的流变行为,并深入分析其变形和移动机理.研究结果表明:在不同的毛细管数下,同心复乳液内部子液滴的存在对复乳液的变形有正反双重作用;双子液滴的不对称分布导致非对称复乳液两侧界面变形和曲率不对称,界面曲率差驱使母液滴在延展流中发生移动.

曲率与界面传质

简要总结了曲率与扩散驱动力的关系:化学势差与曲率成正比线性关系,这一关系中存在临界曲率,目前尚没有计算该临界曲率的方法和理论。分别讨论界面曲率在固相界面和固液界面上对界面扩散传质的影响,以及曲率在固态扩散连接和合金凝固等过程当中各与界面相关的理论中的应用。列举实际应用中的一些实例,分析这些实例中的实用性结论和存在的问题。