Compositional mapping of bitumen using local electrostatic force interactions in atomic force microscopy

In recent years, many researchers have investigated bitumen surface morphology, especially the so‐called bee‐like structures, in an attempt to relate the chemical composition and molecular conformation to bitumen micromechanics and ultimately performance properties. Even though recent studies related surface morphology and its evolution to stiffness and stress localization, the complex chemical nature of bitumen and its time‐ and temperature‐dependent properties still engender significant questions about the nature and origin of the observed morphological features and how they evolve due to exposure to various environmental and loading conditions. One such question is whether the observed surface features are formed from wax or from the coprecipitation of wax and asphaltene. Our prior work was mainly theoretical; it used density functional theory and showed that the coprecipitation theory may not stand, mainly because wax–asphaltene interactions are not thermodynamically favourable compared to wax–wax interactions. This paper presents a comprehensive approach based on experiments to study surface morphology of bitumen and conduct compositional mapping to shed light on the origin of the bee‐like surface morphological features. We used Atomic Force Microscopy (AFM), with the main focus being on single‐pass detection and mapping of local electric properties, as a novel approach to enhance existing compositional mapping techniques. This method was found to be highly effective in differentiating various domains with respect to their polarity. The results of our study favour the hypothesis that the bee‐like features are mainly composed of wax, including a variety of alkanes.     

利用井筒稳定性分析确定砂岩安全钻井液密度窗口

以伊朗西南部某油田Asmari组砂岩储集层为研究对象,研究其中一口垂直井的井筒稳定性,利用FLAC3D软件,根据钻遇地层地质力学特征建立井筒的有限体积模型,监测井壁岩石塑性状态的形成以确定砂岩层安全钻井液密度的上限值和下限值。评估了岩石强度特性、井筒周围主要地应力和孔隙压力对该井安全钻井液密度窗口的影响,敏感性分析结果表明,井壁岩石内聚力和内摩擦角的减小会导致安全钻井液密度窗口大幅变窄;孔隙压力和最大水平应力与最小水平应力之比的减小则会使安全钻井液密度窗口显著增大。此模型便于量化安全钻井液密度窗口的变化,可作为一种油气井钻井方案设计和监测工具。图11参50     

Influence of gum tragacanth,Astragalus gossypinus,addition on stability of nonfat Doogh,an Iranian fermented milk drink

In this study, the stabilising property of various concentrations of gum tragacanth in nonfat doogh, an Iranian fermented milk drink, was investigated by measuring phase separation, particle size, flow behaviour and viscoelastic properties. Moreover, light microscopy was used to get more insight into morphological characteristic of protein–polysaccharide complexes in doogh samples. The addition of gum tragacanth improved stabilisation of doogh samples which was associated with an increase in apparent viscosity and storage modulus. Furthermore, the particle size distribution showed an increase in polydispersity and a pronounced reduction in median diameter of protein–polysaccharide complexes which was accompanied by no phase separation at 0.3% concentration of gum tragacanth.     

Surfactant cleaning of ultrafiltration membranes fouled by whey

A polyethersulphone ultrafiltration membrane was prepared for concentration of whey. The membrane was fouled by whey and the effect of different cleaning agents on flux recovery of the fouled membrane was studied. The optimum cleaning procedure for membrane regeneration was elucidated. The results showed that a combination of surfactants (anionic, cationic and nonionic) may be employed as the optimum cleaning agent for maximum flux recovery. The fluorescence studies revealed that the cationic surfactant interact with proteins by breaking the intra‐chain hydrophobic bonding and providing electrostatic repulsion. Changing the alkyl chain from dodecyl to hexadecyl increases the interaction of surfactant–protein. Dodecyltrimethylammonium bromide (DTAB) provided a weak interaction with whey proteins than to tetradecyltrimethylammonium bromide (TTAB) and cetyltrimethylammonium bromide (CTAB). All data obtained in this study support a surfactant–protein interaction in which hydrophobic forces play a dominant role. The nonionic surfactants poly(oxyethylene) isooctyl phenyl ether (TX‐100) and anionic surfactants SDS interact with amino acids in the inner protein structure thus denaturate tertiary protein structure and reduce hydrophobic interaction of proteins by membrane surface.     

TRANSIENT ANALYSIS OF CAPACITOR SWITCHING IN UNBALANCED DISTRIBUTION SYSTEM WITH HARMONIC DISTORTION

ABSTRACT

The wide application of shunt capacitor banks in distribution systems for economic reasons, have raised concern about over-voltage transients and harmonic magnification in unbalanced distribution systems. This paper introduces a new method for transient analysis during capacitor switching. Presence of harmonic sources, unbalance in feeder configuration, and combinations of single-and three-phase loads are accounted for. The new method is a frequency domain-based approach using a three-phase Z-Bus algorithm. The paper reviews the concepts of the building algorithm of a three-phase Z-bus matrix in the complex frequency domain. Untransposed feeders and different types of loads are considered. Finally, the boundary conditions for different capacitor switching cases and the results with harmonic distortion are reported.     

Effect of whey protein concentrate addition on the physical properties of homogenized sweetened dairy creams

The influence on their whipping properties of homogenization at first and second stage pressures of 3.5/1.5 MPa and addition of whey protein concentrate (WPC) powder at three different (0.7, 1.4, and 2.1 wt percentage) concentrations to sweetened and homogenized creams was studied. Homogenization of cream significantly decreased maximum overrun and made the foam microstructure less open, while increasing whipping time, cream and foam lightness (Hunter L -value) and apparent viscosity. It also resulted in a less elastic foam structure with an increased drainage. Addition of WPC decreased the amount of maximum overrun, foam drainage and its lightness in parallel with developing a more compact microstructure. It increased the whipping time, apparent viscosity of unwhipped creams and foams, and resulted in a less elastic foam structure. The apparent viscosity of whipped cream with 2.1 wt percentage WPC, however, was lower than that of whipped cream with 1.4 wt percentage WPC, due most probably to the start up of gel formation at 2.1% WPC concentration in sweetened cream when it was sheared. Fresh foam whipped from sweetened cream with 2.1 wt percentage WPC also tended to have a slightly but not statistically significant lower elastic modulus (G') than fresh foam whipped from sweetened cream with 1.4 wt percentage WPC. This concentration can be considered as the critical value for gel formation in sweetened creams enriched by whey proteins when sheared. This study indicated the potential of WPC powder for reducing foam drainage from whipped homogenized sweetened cream.