The Viscous Drag of a Rough Cylinder in a Liquid Flow in a Porous Medium

The general solution to Brinkman's equations in a cylindrical coordinate system is obtained. This solution is used to calculate the viscous drag of a rough cylinder (placed in a porous medium) with an arbitrary orientation of its axis in relation to the velocity of the advancing flow. A formula is derived for the viscous drag of the cylinder as a function of the concentration of particles that have deposited on it during the initial stage of filtration.     

The Use of the Finite-Element Method for Calculating the Photophoresis Force Applied to a Large Spheroidal Aerosol Particle

Colloid Journal - The finite-element method has been employed to calculate the photophoresis force applied to a solid spheroidal aerosol particle, the size of which is much larger than the mean...     

Estimation of Outlet Temperature of a Flow Reactor Heated by Microwave Irradiation

Flow reactors heated by microwave irradiation attract attention. The reactors are suitable for difficult synthesis processes due to rapid heating and cooling, and easy pressurization. In order to predict the quality of the product, it is appropriate to estimate the outlet conditions of the reactor. In this paper, the outlet temperature of the flow direction is estimated by using the flow condition and dynamic thermal energy balance of the reactor.     

Flow around a capsule with a fractal core

The problem of a liquid flow that is uniform at infinity around a capsule containing a fractal aggregate is solved. The flow in the porous layer of the capsule is described by the Brinkman equation, assuming that the viscosity of the Brinkman medium differs from the viscosity of the pure liquid. The tangential stress jump condition is imposed on the liquid-porous medium interface. Velocity and pressure distributions are found, and the hydrodynamic force applied to the capsule is calculated.     

Viscous Flow Parameters of Mixed Nonionic Surfactants Microemulsions

The systems investigated were water/sucrose laurate/ethoxylated mono-di-glyceride/oil + ethanol. The oils were R (+)-limonene, isopropylmyristate and caprylic-capric triglyceride. The dynamic viscosity of the systems where the mixing ratio (w/w) of ethanol/oil and that of ethoxylated mono-di-glyceride/sucrose laurate equal unity were measured. Dynamic viscosity was measured as function of temperature at different water volume fractions. The measured viscosities for the samples in all of the systems decrease as the temperature increases. The thermodynamic parameters of viscous flow that include enthalpy, entropy, and Gibbs free energy were estimated. In all of the systems studied, the enthalpy of viscous flow remains constant as function of temperature and varies as the water content in the microemulsions vary. The entropy and the Gibbs free energy vary with both the temperature and the composition of the microemulsions. Linear relationships were observed between the enthalpy and entropy of viscous flow for the systems based on the three oils. The enthalpy-entropy compensation temperatures were determined and found to be 265, 349, and 322 K for the microemulsion systems based on R (+)-limonene, isopropylmyristate and caprylic-capric triglyceride, respectively.     

流动条件下两种不同亲水基团咪唑啉型缓蚀剂的缓蚀性能

选择了两种含有不同亲水基团的咪唑啉型缓蚀剂, 即1-胺乙基-2-十一烷基咪唑啉(AEI-11)和1-羟乙基-2-十一烷基咪唑啉(HEI-11), 分别在静态及动态条件下,采用失重法、极化曲线法、电化学阻抗谱法研究了上述缓蚀剂对N80钢在CO2饱和的3%(w)NaCl溶液中的缓蚀性能. 研究结果表明, 无论在静态和动态条件下, HEI-11均表现出更佳的缓蚀性能, 即咪唑啉型缓蚀剂的缓蚀性能与亲水基团的极性成正比; 在流动条件为5 m·s-1时, 缓蚀剂的缓蚀效率显著降低. 为了进一步研究缓蚀剂的缓蚀性能与其结构的关系, 运用量子化学法计算了缓蚀剂的EHOMO(最高占有分子轨道)、ELUMO(最低空分子轨道), 结果表明缓蚀剂的缓蚀效率与EHOMO成正比, 与ELUMO及ELUMO与EHOMO的差值驻E成反比.     

Flow of a liquid-crystalline polymer solution around an obstacle

The behaviour of an anisotropic solution of hydroxypropylcellulose around an obstacle is investigated in shear and during relaxation. Experiments were carried out with an optical rheometer equipped with transparent cone-and-plate. The obstacle is a 200 micron glass sphere stuck on the plate. A typical Reynolds number past the obstacle is about 10^-5. The flow of the anisotropic solution perturbed by the obstacle shows specific phenomena: distorted downstream streamlines, a very long wake behind the obstacle during shear which persists a long time after the ceasing shear, a change in the behaviour at very high shear rates and in particular, the appearance of a wake in front of the obstacle. To date there has not been any theoretical bases with which to explain these new findings. An interesting point is that the wake behind the obstacle is a good illustration of the problem of weldlines in injection moulding.     

Forces between a Rigid Probe Particle and a Liquid Interface

The effect of disjoining pressure between a rigid spherical probe particle (attached to an AFM cantilever) and a liquid interface (e.g., oil/water or air/water) is treated in an analytic manner to describe the total force F exerted on the probe as a function of the distance X of the probe from the rigid substrate (AFM stage) on which the liquid interface resides. Two cases (i) a flat interface under gravity and (ii) a drop whose size is sufficiently small that gravity can be neglected have been examined. A simple numerical algorithm is given for computing F(X) (the AFM observable) from a given form for the disjoining pressure. Numerical results are displayed for electrostatic probe/interface interactions which reveal the linear compliance regime experimentally observed in AFM experiments on these systems. The slope of the linear compliance regime is shown to be a function of the properties of the interface (capillary length, particle radius, drop size, contact angle of drop on rigid substrate etc.). Copyright 2001 Academic Press.     

Phase Transitions of the Liquid–Liquid Type and a Change in the Particle Charge in Colloidal Solutions

The thermodynamic properties are studied for the solutions of charged colloidal particles with ionizable surface groups. The microscopic mechanism of microion binding at surface groups is considered. The free energy of the system in the parameter range where the usual theory of such solutions is inadequate (a range of practical interest) is calculated using the method of the thermodynamic perturbation theory. The first-order phase transition of the liquid–liquid type is shown to be possible; in this phase transition, a phase with a high concentration of colloidal particles that have a higher charge coexists with a phase with a lower concentration of particles that have a lower charge.     

液相色谱-电喷雾质谱/质谱法测定高温烹制的淀粉类食品中的丙烯酰胺

以C18反相色谱柱为分析柱,以0.1%甲酸水溶液-甲醇(体积比为98∶2)为流动相,采用同位素稀释液相色谱-电喷雾 质谱/质谱(LC-MS/MS)技术对加热淀粉类食品中的丙烯酰胺进行了测定。利用Oasis HLB固相萃取柱对样品进行净化。方 法的线性范围为10～500 μg/L,线性相关系数为0.9995。方法的定性检出限为6 μg/kg,定量检出限为20 μg/kg。高 、中、低3个浓度水平的加标回收率为96.8%~97.4%,相对标准偏差小于10%。     

Electrical Potential Distribution around a Charged Colloidal Particle: Nonlinear Integral Equation

多电解质溶液中带电胶体粒子的电势分布由球形Ｐｏｉｓｓｏｎ－Ｂｏｌｔｚｍａｎｎ方程（ＰＢＥ）描述．ＰＢＥ是一个非线性的微分方程，且难以求得其解析解．本文采用非线性Ｐ－Ｂ积分方程，计算电势分布的数值解．首先，根据静电场和热力学系统中的物理定理，导出描述电势分布的Ｐ－Ｂ积分方程（ＰＢＩＥ）；其次，用迭代方法求ＰＢＩＥ的数值解．最后，计算了在３－１型电解液中无量纲半径κａ分别为０．１２和０．２２，无量纲表面电势ξ分别为１，２，４，６时球形胶体粒子外部的电势值．为了检验数值解的精度，计算了表面电荷密度，并与Ｌｏｅｂ（１９６１）和Ｏｓｈｉｍａ（１９９５）等人的结果比较，本文结果的相对误差小于１％，优于Ｏｓｈｉｍａ的结果．     

Path Integral Molecular Dynamics of Liquid Water in a Mean-Field Particle Reservoir

We present a simulation scheme for path integral simulation of molecular liquids where a small open region is embedded in a large reservoir of non interacting point-particles. The scheme is based on the latest development of the adaptive resolution technique AdResS and allows for the space-dependent change of molecular resolution from a path integral representation with 120 degrees of freedom to a point particle that does not interact with other molecules and vice versa. The method is applied to liquid water and implies a sizable gain regarding the request of computational resources compared to full path integral simulations. Given the role of water as universal solvent with a specific hydrogen bonding network, the path integral treatment of water molecules is important to describe the quantum effects of hydrogen atoms’ delocalization in space on the hydrogen bonding network. The method presented here implies feasible computational efforts compared to full path integral simulations of liquid water which, on large scales, are often prohibitive.     

Flow of liquid around the encapsulated drop of another liquid

The problem of the infinite uniform flow of liquid around the spherical drop coated with the porous layer is solved. External liquid permeates into the porous layer but is not mixed with the liquid located in the internal cavity of a capsule. The flow inside the porous layer is described by the Brinkman equation; moreover, the viscosity of the Brinkman medium is assumed to be different than the viscosity of pure liquid. The boundary condition of the jump of tangential stresses at the liquid-porous medium interface is used. Velocity and pressure distributions are found and the hydrodynamic force acting on the capsule is calculated. Different limiting cases are considered.     

Viscosity and Thermodynamics of Viscous Flow for the Systems of Isomeric Pentanols with Toluene

Viscosities of the isomers of pentanol (1-pentanol, 2-pentanol and 3-pentanol) and their binary solutions with toluene in the whole range of composition have been measured at different temperatures between 303.15 and 323.15 K. Viscosities of pure components have been plotted against temperature and for binary mixtures, against the mole fraction of pentanols at different temperatures. At lower concentrations of pentanols, viscosities increase slowly, but at an increasing rate on the continued addition of pentanols in toluene. The excess viscosities and excess free energies of activation for viscous flow are in the order, 3-pentanol + > 2-pentanol + > 1-pentanol + toluene. Excess entropies are found to be negative for the systems 2-pentanol + toluene and 3-pentanol + toluene in the whole range of composition, but for 1-pentanol + toluene the values are small and they are either positive or negative at different compositions. The disruption of H-bonds in pentanols either by thermal effect or by the force of dispersion is in the order: 3-pentanol > 2-pentanol > 1-pentanol. This effect is considered to be quite significant in explaining the temperature dependence of viscosity of pure pentanols, negative excess values of viscosity, free energy and entropy for viscous flow as well as their orders for all the systems.     

The Two-Component Fiber Row: Viscous Drag and Particle Deposition in the Regime with Interception

Theoretical expressions for a mean resistance force of a random two-component fiber row and a mean deposition efficiency of aerosol particles in this row in the regime with interception were derived. The effect of gas slip near the fibers was considered. It was shown that the derived formulas well describe the results of numerical simulation, including the modeling of the dense rows with wide fiber size distribution. Comparison with the experimental data was made.     

Viscous Flow Through Polydisperse Row of Parallel Fibers: Account for the Slip Effect

A general theory of the flow through the flat periodic row of parallel polydisperse fibers randomly arranged at the fiber period is elaborated. An approximate solution of the problem with account for the slip effect at low Reynolds numbers is obtained for normal incident flow. The system of equations for determining local drag forces acting on each fiber in a row, as well as the system of equations for determining local buoyancy forces, are derived. It was demonstrated that, in the approximation obtained, the buoyancy forces are equal to zero, provided that bilateral symmetry is present in the fiber arrangement. The behavior of local forces as a function of row parameters is considered using bimodal row as an example. The form of flow function is established for the velocity field near the arbitrary fiber.     

On the General Expression for the Electrophoretic Mobility of a Soft Particle

Electrokinetic equations for electrophoresis of a soft particle (that is, a hard particle covered with a layer of polyelectrolytes) have been solved previously under the conditions that the net force acting on the soft particle as a whole (the particle core plus the polyelectrolyte layer) must be zero and that the electrical force acting on the polymer segment is balanced with a frictional force exerted by the liquid flow (J. Colloid Interface Sci. 163, 474 (1994)). In the present work we replaced the latter condition by the alternative and more appropriate condition that pressure is continuous at the boundary between the surface layer and the surrounding electrolyte solution to solve the electrokinetic equations and obtained the general mobility expression for the electrophoretic mobility of a spherical soft particle. It is found that the general mobility expression thus obtained reproduces all of the approximate mobility expressions derived previously and, in addition, that the continuous pressure condition leads to the correct limiting behavior of the electrophoretic mobility in the case where the frictional coefficient tends to zero (this behavior cannot be derived from the force balance condition for the polyelectrolyte layer). Copyright 2000 Academic Press.     

An Experimental Investigation of the Liquid Flow Induced by a Pulsed Electrical Discharge Plasma

In this work, particle image velocimetry has been used to visualize and quantify plasma-induced flow fields in liquid water. Experiments were performed in a rod-plane plasma reactor with a thin wire electrode suspended above the surface of the liquid in argon gas and a grounded plate immersed in the liquid. The velocity field has been quantified for two types of solutions: (1) aqueous NaCl solutions of varying solution conductivities and discharge frequencies and (2) aqueous NaCl solutions containing varying concentrations of the following four organic compounds: rhodamine B dye, caffeine, fluoxetine, and perfluorooctanoic acid. Results show that in neat water and aqueous caffeine solutions, the liquid is “pulled” along by the interaction of the gas molecules with the liquid molecules at the free surface and thus the direction of the liquid flow is in the direction of the gas phase flow (i.e., away from the discharge location). However, the flow was reversed (i.e., towards the discharge) for those solutions with strong surfactants such as perfluorooctanoic acid. The magnitude of the reversal depended on the initial concentration of the compound and for some compounds as time progressed the reversed flow pattern weakened and then reverted to a normal flow pattern. To determine the most likely cause of these flow reversals, a simple numerical model of the velocity field was developed to estimate relative contributions of various flow inducing mechanisms. The model indicates that in the presence of surfactants, Marangoni stresses are responsible for inducing the flow in the liquid.     

粒子束接口液相色谱－质谱应用

粒子束接口液相色谱－质谱应用黄峰（山东大学发酵工程国家实验室济南２５０１００）１前言化学和生物样品中的热不稳定性组分及难挥发性组分无法用气相色谱。质谱进行分析，因此液相色谱。质谱联用倍受关注。近二十年来发展了许多技术，如直接液体导入（ｄｉｒｅｃｔｌｉ...