Rheological studies of hyaluronan solutions based on the scaling law and constitutive models

We have investigated the scaling relationship between rheological behavior and concentration for both salt-free and saline solutions of hyaluronan (HA), and adopted three viscoelastic constitutive models to predict the linear/non-linear viscoelastic behavior of these aqueous solutions of HA with different molecular weights at different concentrations up to 20 mg/ml. A series of concentration equations are obtained to describe the influence of HA concentration on solution viscosity. Corresponding to dilute and semi-dilute concentration region, salt-free HA solutions have scaling relationship between specific viscosity and HA concentration as η_sp ∼ c^1.0 and η_sp ∼ c^3.5, respectively, while for 0.15 M NaCl HA solutions, the scaling exponents are 1.5 and 4.2, respectively. Simulation results indicate that these constitutive models have good applicability to describe quantitatively the rheological properties of HA entangled solutions under either dynamic or steady shear flow. In addition, the plateau modulus scaling of HA solutions can be well described by the concentration-dependent length scale.     

Experimental investigation and theoretical modeling on scale behaviors of high salinity wastewater in zero liquid discharge process of coal chemical industry

Zero liquid discharge (ZLD) treatment and reuse equipment of high salinity wastewater in coal-chemical industry often occur in various types of blockage problems because of high salt content, affecting the long-term stability of the device. In this study, the effects of solution temperature, steel, reaction time and wall roughness on fouling were investigated. The changes in the contents of fouling and fouling substances were qualitatively and quantitatively analyzed by XRD and EDS respectively, and the formation of scale was observed by SEM. The results show that with temperature increasing, Q235 steel is the most difficult to scale. Scaling rate of all salt scales reaches a maximum after 12 h, and the fouling rate decreases significantly from 12 to 48 h. It gradually stabilizes at 48 to 96 h. With the roughness increasing, the thickness of fouling layer increases, and a linear relationship is presented for 1 to 10 h. By comparing actual and simulated wastewater scaling rates, the relationship between actual and simulated wastewater scaling rates is y=ax^-0.494. The composition of the scale was analyzed, calcium carbonate is the main product and increases with fouling time. Based on the above-mentioned results combining literatures, the hybrid prediction model with calcium carbonate as the main product is put forward. It is discussed microscopically that calcium carbonate is converted from aragonite and vaterite in a thermodynamically metastable state to calcite in a thermodynamically stable state.     

Using the concept of a measurement system to characterize measurement models used in psychometrics

The philosophy of measurement in the social and behavioral sciences is seen (from without) as typically following the representational viewpoint. However, in practice, this is not the case for the great majority of measures that are developed in this area. The paper surveys several approaches to measurement in the social sciences (i.e., Classical Test Theory, Guttman Scaling, Item Response Theory, Rasch Scaling, and Construct Modeling), as examples of measurement approaches in the area of psychometrics, and uses the foundational concept of a measuring system, as developed by Mari [1], to explicate the logic on which these approaches are based and thus enable a comparison with measurement approaches used by other fields such as engineering and physics. The paper uses the underlying concept of the standard reference set (one of the essential features of Mari’s formalization) to show how the five approaches differ, and also how they are related. The importance of these differences, and the consequences for measurement using those approaches are also explicated and discussed.     

环道实验研究碳酸钙结垢规律

我国出产的石油大多数属于重油,结垢问题严重。通过设计环道实验,发现随着流速的增大,碳酸钙结垢诱导期加长,结垢速率减小,渐进污垢热阻减小;表面温度越高,结垢速率越大。之前的文献中很少讨论碱度对换热表面结垢的影响,本文对不同硬度及碱度含量的水质进行了实验研究发现,碱度越大结垢越严重;随着溶液硬度的增大,结垢速率先是增大,待增大至一定浓度时降低。     

基于非平稳时间序列双标度指数特征的齿轮箱故障诊断

齿轮箱振动信号是含噪的多分量非平稳信号,故障模式相近的复杂齿轮箱振动信号的分类是齿轮箱故障诊断的难点。采用去趋势波动分析(Detrended fluctuation analysis,DFA)方法分析齿轮箱振动信号的标度行为,随着时间尺度的增大,标度指数会突然发生改变,形成双标度指数特征,由双标度指数构成的二维矢量具有明确的物理意义,可以作为表征时间序列内部动力学机制的特征参数。提出一种基于非平稳时间序列双标度指数特征的齿轮箱故障诊断方法,对正常状态和含有轻度磨损、中度磨损和断齿故障的齿轮箱故障诊断的结果表明,提出的方法成功地解决了故障模式相近的复杂齿轮箱振动信号的分类问题,很好地克服了傅里叶变换、小波变换和基于单标度指数的方法存在的缺陷,为齿轮箱的故障诊断提供了一种新的方法。     

轮南油田注水系统结垢趋势预测

本文针对轮南油田油水系统的特点,对碳酸盐垢,硫酸盐垢的结垢趋势分析进行了理论预测,同时对室内防真模拟实验结垢样品进行了Ｘ射线衍射分析,理论预测结果表明,轮地油田注水系统中可能会形成碳酸盐垢但不会形成硫酸盐后,理论预测和室内仿真实验结果完全相符,本文为轮南油田注水系统选择合适的阻垢剂提供了依据。     

Preference for newspaper size

The past few years has seen a change in the size of newspapers, with publishers moving to a smaller size format. Five ‘standard’ newspaper sizes are used in different countries: Broadsheet, Rhensch, Tabloid, Tall Tabloid and Berliner. These papers vary in both width and height of pages and hence there are implications for human reading comfort, which may be dependent on reading location such as on a lounge chair or on a train. Experiments were carried out to determine preferences for the different sizes and to relate these preferences to the geometric characteristics of the newspapers. For both comfortable and cramped/uncomfortable reading conditions, the rank order of preference for paper types was, from least to most-preferred, Broadsheet, Rhensch, Berliner, Tall Tabloid and Tabloid. Preferences were much stronger when determined in cramped/uncomfortable reading conditions, where most comparisons were significantly different. There was good correlation between participant ratings on several scales and preference, where most factors were related to comfort of holding and controlling the paper.     

CFD modeling of multiphase flow distribution in catalytic packed bed reactors: scale down issues

Flow maldistribution in either a bench-scale or commercial scale packed bed is often responsible for the failure of the scale down unit to mimic the performance of the large reactor. The modeling of multiphase flow in a bench-scale unit is needed for proper interpretation of reaction rate data obtained in such units. Understanding the mechanism of flow maldistribution is the first step to avoiding it. In order to achieve this objective, computational fluid dynamic (CFD) simulations of multiphase flow under steady state and unsteady state conditions in bench-scale cylindrical and rectangular packed beds are presented for the first time. The porosity distribution in packed beds is implemented into CFD simulation by pseudo-randomly assigned cell porosity values within certain constraints. The flow simulation results provide valuable information on velocity, pressure, and phase holdup distribution.     

A needs based methodology for classifying construction clients and selecting contractors-a rejoinder

Our original article (Chinyio et al., 1998a) ‘A needs based methodology for classifying construction clients and selecting contractors’, Construction Management and Economics, 16 (1), 91-98 discussed the empirical classification of construction clients and illustrated a new methodology for selecting contractors. The techniques we adopted have not been applied in a construction scenario before and thus their implementation may face teething difficulties as differences between construction and the disciplines from which the techniques were adopted are ironed out. Due to brevity we did not highlight some of the potential problems their implementation would encounter, as we could not explain everything on the subject matters in one article. Skitmore and Mills (1999) in a comment, Construction Management and Economics, 17 (1), 5-7, highlighted some anticipated difficulties and posed some insightful questions concerning the applicability of our concepts. From an optimistic perspective we have addressed most of the sundry issues raised by Skitmore and Mills wherein ‘Decision Analysis’ was reviewed as a basis for responding to the comments.     

Effects of Process Parameters on Gypsum Scale Formation in Pipes

Scaling often leads to a series of technical and economical problems in industrial plants and equipments by blocking water flow in pipes or limiting heat transfer in heat exchangers. While most contemporary studies are focusing on crystallization at heat‐exchanger surfaces and scaling on nanofilters in desalination plants, very little work has been done investigating scale formation on pipe and vessel walls. A comprehensive investigation of the effects of various process parameters in controlling the formation of calcium sulfate scale in pipes was undertaken. Supersaturation ratio, run time, and operational hydrodynamics were altered systematically to determine their influence on the scale growth rate. The results confirmed that the deposition of gypsum on pipe walls was significantly affected by these process parameters.