Hydrodynamic properties and conformation of poly(3‐hexylthiophene) in dilute solutions

Conducting polymers demonstrate low solubility in organic solvents. Introducing aliphatic substituents into polymer chains improves their solubility, but may also lead to changes in conformational characteristics of macromolecules. In the present work, the studies of hydrodynamic properties and conformational characteristics of comb‐shaped poly(3‐hexylthiophene) with aliphatic side substituents were carried out in chloroform solutions. Conformational analysis of the studied macromolecules was performed for the first time using homologous series with a wide range of molecular weights of the polymers in dilute solutions. The hydrodynamic properties of these macromolecules were interpreted using the worm‐like spherocylinder model and the straight spherocylinder model. The projection of the monomer unit in the direction of the main polymer chain λ = 0.37 nm was determined experimentally. The following parameters of poly(3‐hexylthiophene) were characterized and quantified: equilibrium rigidity (Kuhn segment length) А = 6.7 nm and hydrodynamic diameter of a polymer chain d = 0.6 nm. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016 , 54, 875–883     

Formation of regular clusters through self-association of intramolecularly hypercrosslinked polystyrene-type nanosponges

Atactic polystyrene of M = 330,000 Da and M_w/M_n = 1.04 was subjected to chloromethylation. By the heating of chloromethylpolystyrene with SnCl₄ in a very dilute solution in ethylene dichloride, the polymeric coils were converted into intramolecularly hypercrosslinked macromolecules, nanosponges, of molecular weight of about 370,000 Da and a diameter of about 17 nm. When in solution, the nanosponges tend to reversibly self-assemble into regular clusters. Size exclusion chromatography and sedimentation analysis corroborate the suggestion that the clusters consist of 13 spherical subunits and thus acquire a molecular weight of about 5.0 × 10⁶ Da and a diameter of about 45 nm. © John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 3847–3852, 1997     

Preservation potential of individual couplet and deposition rates on mudflats in the Changjiang Estuary

Non-barrier mudflats in the Changjiang Estuary is examined to obtain preservation potentials and deposition rates over different time scales. The preservation potential of couplet is ca. 46.6% within daily scale and decreases as the time-interval extending, with 9.2% on a semi-lunar scale and 3.7% on a seasonal scale. In the long term, only 1.6% of daily deposition can potentially be preserved in the tidal flat sequence and other 98.4% have been eroded and leave sedimentary discordances, discernable or un-discernable, in the mudflat deposits. A negative log-linear relationship is examined between sedimentation rates and the time spans. The length of sedimentary hiatuses on the mudflat deposition were estimated with considerable uncertainty, but it can provide from an actualistic base some further insights into the nature and origin of ancient mudflat deposits with emphasis on the sedimentary discordances.     

A physical,mechanistic and fully coupled hillslope hydrology model

We present the mathematical development and numerical solution of a new model of flow processes on an infiltrating hillslope. We also present validation and sample applications. The model is a distributed, mechanistic, physically based hillslope hydrologic model. The model describes the small‐scale processes associated with overland flow, erosion, and sediment transport on an infiltrating surface and is capable of capturing small‐scale variations in flow depth, flow velocities, interactive infiltration, erosion rates, and sediment transport. The model couples the fully two‐dimensional hydrodynamic equations for overland flow, the one‐dimensional Richards equation for infiltration, and a sediment detachment and transport model. Two simulations are presented highlighting the model's ability to capture and describe the interaction between precipitation, overland flow, erosion and infiltration at very small scales. Results of the two‐dimensional simulations indicate the system of equations produces hillslopes possessing characteristics of self‐organization as observed in real world systems. Copyright © 2005 John Wiley & Sons, Ltd.     

Studies on Separation of Liquid‐Liquid Dispersions: Diesel‐Water System in Batch Settler

In this article, batch settling of liquid‐liquid dispersion in a vertical batch settler was comprehensively studied. The experiment results of the investigation on liquid‐liquid batch settler phase separation were compared with a well predefined physical model proposed by Jeelani and Hartland [1998, Ind. Eng. Chem. Res. 37: 547–554] using a semi theoretical approach. The effect of initial dispersion height, initial hold‐up volume, settler diameter, and mixing time on separation of batch liquid‐liquid dispersions were experimentally investigated in terms of variation in the final settling time and coalescing interfaces with time. From the present work it was found that, final separation time varied as polynomial function of degree 2 with respect to initial dispersion height and was constant with respect to initial hold‐up volume. Final separation time also varied according to the completeness of dispersion achieved with respect to the mixing time. The experimental data obtained showed a good correlation with the theoretically predicated values. Results allow the use of experimental procedure with the mathematical model as a tool in monitoring the dispersion behavior in commercial units on industrial importance.     

Electrophoresis and Sedimentation of Charged Fibers

The electrophoretic translational and rotational velocities of a fiber are determined in the limitsL/d≥≥ 1 and λ/d≥≥ 1, where λ is the double layer thickness andLanddare the fiber length and diameter, respectively. The fiber translates due to the imposed electric field at a rate that increases with increasing double layer thickness. A nonuniformly charged fiber with a net charge dipole rotates until it becomes aligned with the electric field. The results for the translational and rotational velocities are obtained in a semianalytic form. The effect of the deformation of the ion cloud surrounding a charged sedimenting fiber on the fiber's translational and rotational velocities is also determined. The ion cloud retards the sedimentation velocity relative to that of an uncharged fiber with the same orientation. If the fiber possesses both a net charge and a charge dipole, it will rotate into a vertical alignment in which the end with the larger absolute charge is on top.     

Sedimentation behavior of high-temperature concentrated colloidal suspension based on potassium cryolite

The paper describes the sedimentation behavior of concentrated high-temperature oxide-fluoride slurries with alumina particles volume fraction range 0.24?≤?φ?≤?0.32 at ～700 °C. The behavior is of interest due to perspectives of the non-Newtonian fluids usage in the future aluminium reduction technology. To characterize sedimentation behavior several techniques were used: density analysis, X-Ray diffraction, microphotography and electron scanning microscopy. Sample with ?63?µm dispersed phase as well as smelter-grade alumina which contains particles in a range of 10–150?µm has been examined. It has been found that particle settling occurs with the initial velocity 0.97·10^?5 m·s^?1 at φ?=?0.24 and gradually reduces reaching zero at φ close to 0.32 which was considered as a maximum packing fraction. MS^?1 sedimentation mode has been identified, the type of sedimentation was found to be changed from type 1 to type 3 in the sample with φ?=?0.24. The alumina partial density distribution in suspension as a function of time was determined. Alumina average motion velocity during sedimentation was calculated to be 154·10^?3?kg·m^?2·s^?1 at φ?=?0.24 in the top layer of the sample within the first 150?s of sedimentation. It had been reducing drastically before it reached zero after 300?s. An alumina flow was higher in the top layers. Some of the rheological properties (such as relaxation time, which increased from 7.2·10^?3 to 17.7·10^?3?s after the increase of φ from 0.24 to 0.28) has been determined.     

壁面约束对柱状粒子在牛顿流体中沉降影响的研究

格子Boltzmann方法(LBM)直接数值模拟了在有壁面约束的流场中柱状粒子的沉降。结果说明粒子在壁面的影响下，会离开管壁向管中心移动，移动速度先是增大，然后随着与管壁距离的增加，逐渐减小，粒子中心最后并不一定停留在管中心。随着粒子与壁面距离的增加，粒子的沉降速度将增大，可见壁面对粒子沉降有阻碍作用，平行于粒子轴线的壁面对粒子沉降的影响比垂直于粒子轴线壁面的影响大。     

MIXED FINITE ELEMENT METHODS FOR THE SHALLOW WATER EQUATIONS INCLUDING CURRENT AND SILT SEDIMENTATION （Ⅰ）——THE CONTINUOUS-TIME CASE

An initial-boundary value problem for shallow equation system consisting of water dynamics equations, silt transport equation, the equation of bottom topography change, and of some boundary and initial conditions is studied, the existence of its generalized solution and semidiscrete mixed finite element (MFE) solution was discussed, and the error estimates of the semidiscrete MFE solution was derived. The error estimates are optimal.     

Mathematical Analysis of the Effect of Sedimentation and Compaction on Steady Transport Profiles in Sediments

Based on fundamental principles transport equations are derived for components in sediment layers. These differ from the usual formulation by the fact that compaction of sediments is explicitly considered. Compaction without doubt plays a significant role in the processes of early diagenesis. As an effect of compaction changing porosity can be observed in sediment profiles. In the paper analytical solutions are derived for cases in which porosity logs show an exponential shape. Comparison with those solutions, which are obtained for the constant porosity (i.e., no compaction) situation, show the relevance of the theoretically rigorous formulation, which is therefore recommended for implementation in computational models.