土体标度分布参数与其物理力学性质的关系研究

土体标度分布参数可以客观地表达土体颗粒组成的整体特征,便于建立其与土体物理力学性质之间的定量关系,具有重要的理论意义和实际应用价值.以土体的标度分布理论为基础,结合土体渗透实验和直剪实验,研究了土体标度分布参数与其渗透系数、抗剪强度指标(黏聚力、内摩擦角)的关系,结果表明:土体渗透系数K与标度分布参数μ呈负对数关系,与...     

天然高分子溶液流变性研究进展

天然高分子是一种储量丰富的可再生资源,在许多领域有广泛的应用前景。流变学作为研究天然高分子溶液的性质具有独特的优势。通过流变学研究能够获得许多溶液的性质,包括溶液粘弹性变化规律、溶胶凝胶转变条件和高分子链在溶液中的运动学等信息,并能为天然高分子溶液纺丝等应用提供一定程度的理论支持。综述了近几年来纤维素、甲壳素、壳聚糖、天然蛋白等天然高分子在离子液体/有机试剂、纯离子溶剂,以及氢氧化钠尿素水溶液等溶剂体系中的流变性研究进展,并对天然高分子溶液的流变学理论发展和溶解技术进行了展望。     

含引发机制的A_(f-)A_g型缩聚反应的标度研究

讨论了含引发机制的Af-Ag型缩聚反应体系,根据该反应体系的数量分布函数,导出凝胶点附近分布函数和高分子矩的渐进表示式,进一步应用标度变换,得到了描述溶胶-凝胶相变的广义标度律,揭示出含引发机制的Af-Ag型缩聚反应体系的固化过程是一个相变过程。     

溶液中高分子尺寸的测定

溶液中高分子尺寸的测定,广泛用于研究高分子链在溶液中的形态。高分子在稀溶液里的一些性质如表观粘度、扩散速度等都取决于溶液中高分子尺寸的大小。本文推荐一种粘度计,采用粘度法测得高分子溶液的特性粘数,从而计算高分子链的尺寸。原理溶液中高分子的形状和尺寸不仅与其本身的结构有关,还与溶剂性质、溶液浓度以及实     

构象概念主线在高分子物理课程中的实践探讨

高分子物理是高分子以及相关专业的一门基础专业课,课程需要掌握多种高分子的基本概念及性质,并将物理化学及高分子的物理行为相联系讨论。在课程的学习中有一条主线,围绕主线进行总结复习是课程学习的一个重要方法。其中构象概念在高分子物理中起到自始至终的串联作用,可以将高分子物理的进程结构、运程结构、分子链的运动及力学性质串成一线,本文总结了高分子物理教学过程中如何使用构象概念对课程进行教学。     

导热高分子复合材料研究进展

在介绍金属材料、无机非金属材料以及高分子材料导热机理的基础上,介绍了导热填料填充高分子复合材料的导热网链机理和热弹性组合机理2种导热机理,该理论可以解释导热高分子复合材料导热过程中不同的现象和规律;归纳了适用于粒子、纤维等填充的聚合物基复合材料的各种导热模型;讨论了树脂基体、导热填料和温度对于高分子复合材料热导率的影响...     

标度软硬酸碱的新方法

本文根据电负性标度和电负性均衡原理，提出了计算简单离子电负性的近似方法。在此基础上提出了离子电荷（或原子部分电荷）／离子半径与离子（或原子）电负性为参数标度软硬酸碱的新方法。     

撞击流混合器速度信号的混沌识别及标度分析

应用三维激光多普勒测速仪,对浸没循环撞击流混合器内的流场瞬时速度时间序列进行获取,并分别按照自相关函数和功率谱分析方法判定了该信号的混沌特性,确定了该信号的频谱变化范围为0—20 Hz;将K41理论引入到撞击流流场分析,验证了Kolmogorov惯性区标度律在撞击流这一特殊流动形式下的普适性原则;按照标度分析的方法计算出了流场不同截面处的β值,发现其撞击区内变化范围在0.8β1.6,符合分形流场特征;在撞击区内发现了轴向环形区域的存在,揭示了其存在的物理原理;此外,还发现了流体运动形式不同将会影响到转速对β值的作用效果这一规律;最后,对比了实验结果与K41理论值的差别,分析了出现这一差别的原因。     

共聚马来酸酐平平加酯盐类高分子表面活性剂的合成及特性

介绍了共聚马来酸酐平平加酯盐类高分子表面活性剂的合成方法。讨论了反应条件对其性质的影响。在高分子链中 ,同时含有长链阴离子及非离子的高分子表面活性剂对乳液的稳定性及增稠效果优于具有相同链长的同类阴离子及非离子表面活性剂的复配物     

AHP标度适应性问题的随机隐序率

研究了 AHP应用过程中的隐序现象 ,提出 1个用于判断 AHP标度适应性的新指标——随机隐序率RHO,计算了 4种 AHP标度的随机隐序率 RHO,并进行了初步分析     

The Interplay between the Theories of Mode Coupling and of Percolation Transition in Attractive Colloidal Systems

In the recent years a considerable effort has been devoted to foster the understanding of the basic mechanisms underlying the dynamical arrest that is involved in glass forming in supercooled liquids and in the sol-gel transition. The elucidation of the nature of such processes represents one of the most challenging unsolved problems in the field of material science. In this context, two important theories have contributed significantly to the interpretation of these phenomena: the Mode-Coupling theory (MCT) and the Percolation theory (PT). These theories are rooted on the two pillars of statistical physics, universality and scale laws, and their original formulations have been subsequently modified to account for the fundamental concepts of Energy Landscape (EL) and of the universality of the fragile to strong dynamical crossover (FSC). In this review, we discuss experimental and theoretical results, including Molecular Dynamics (MD) simulations, reported in the literature for colloidal and polymer systems displaying both glass and sol-gel transitions. Special focus is dedicated to the analysis of the interferences between these transitions and on the possible interplay between MCT and PT. By reviewing recent theoretical developments, we show that such interplay between sol-gel and glass transitions may be interpreted in terms of the extended F13 MCT model that describes these processes based on the presence of a glass-glass transition line terminating in an A3 cusp-like singularity (near which the logarithmic decay of the density correlator is observed). This transition line originates from the presence of two different amorphous structures, one generated by the inter-particle attraction and the other by the pure repulsion characteristic of hard spheres. We show here, combining literature results with some new results, that such a situation can be generated, and therefore experimentally studied, by considering colloidal-like particles interacting via a hard core plus an attractive square well potential. In the final part of this review, scaling laws associated both to MCT and PT are applied to describe, by means of these two theories, the specific viscoelastic properties of some systems.     

Effects of the Quantity and Structure of Hydrophobes on the Properties of Hydrophobically Modified Alginates in Aqueous Solutions

Summary Alginate is an important polysaccharide with applications in food industry, cosmetics and pharmacy. In this study, three hydrophobically modified alginates with different amount of various hydrophobic groups have been synthesized. Rheology and turbidity measurements have been carried out on polymer solutions in the concentration regime 0.005–2.0 wt %. The rheological results indicate that the introduction of hydrophobic groups induce the formation of intra- or intermolecular associations in the aqueous solutions depending on the polymer concentration and the hydrophobicity. The concentration dependency of the viscosity exhibit different power-law behaviors depending on the concentration regime and the hydrophobic modification. This has been scrutinized in view of theoretical scaling laws presented in the literature.     

Effect of FRP Pipe Scaling on its Adhesive Bonding Strength

Polymer-based materials are emerging as a potential substitute for metallic structures in the oil and gas industry. In this context, fiber-reinforced polymer (FRP) piping is one promising application. An important area of the research pertaining to FRP piping is the connection of pipe sections. Challenges associated with the joining of FRP tubular sections are often considerable, which limits more widespread industrial application. Adhesive bonding is emerging as a promising technique to join tubular FRP structures. The ability to maintain undamaged fiber architecture is a major advantage of adhesive bonding technology. In the present study a strength-of-materials as well as fracture mechanics approach was employed in conjunction with the finite element method to investigate the scaling effects on adhesively bonded tubular sections. It was found that the scaling effects in joined FRP pipe may be significant. For certain composite material configurations the analysis indicated a shift of the region of failure from the pipe structure to pure adhesive (cohesive) failure with increasing pipe diameter.     

冷指实验研究碳酸钡结垢规律

污垢中的主要成分是碳酸钙,还有碳酸钡、硫酸钡、镁盐、硫酸锶等。国内外学者对碳酸钙结垢规律的研究很多,对碳酸钡的研究相对较少一些。通过冷指实验,控制离子浓度、反应温度、pH值、反应时间和搅拌速度以及溶液的过饱和度,以研究这些参数对碳酸钡结垢的影响。结果表明,碳酸钡垢的生长速率随着温度的增加而增加,随着流速的增加而减小,pH为9时最小,浓度对其生长速率的影响不甚明显。利用冷指实验研究碳酸钡结垢规律是一种较新的方法,其研究成果为油田除垢防垢提供一定的理论依据。     

Scaling law on particle-to-fiber formation during electrospinning

The development of various morphologies such as beads, beaded fibers, pure fibers and their scaling as a function of solution properties and processing variables in electrospinning is reported. Polyvinyl pyrrolidone (PVP), at various molecular weights and concentrations dissolved in a mixture of water and ethanol, was used to prepare different morphologies and sizes. The morphology of beads and fibers was predicted and measured based on an entanglement number diagram and rheological measurements. A constant-current electrospinning system was employed to control the processing variables. Scaling laws related to solution properties and processing variables (voltage, current and flow rate), and their effect on the fiber/bead diameter, were discussed. Viscosity (η), flow rate (Q), and current (I) were found to play significant roles in the control of morphology during electrospinning. Processing variables involved in electrospinning followed a power scaling that was in agreement with the model. The dependence of fiber diameter (d_f) on the Q/I for different molecular weights and concentrations also followed a power law, and the scaling varied between 0.11-0.29 for beaded fiber and 0.36-0.51 for pure fiber. In addition, the relationship between viscosity and fiber diameter followed scaling laws: d_f ∼ η^0.98.     

Planar Brush of End-Tethered Molecular Bottle-Brushes. Scaling Mode

We present a scaling theory describing structural properties of brushes formed by molecular bottle-brushes tethered by the ends of the main chains to inert planar surface. We consider bottle-brushes where q ≥ lateral side chains (grafts) emanate from each of the branching points regularly distributed along the main chain (backbone). Such macromolecule can be envisioned as an array of polymer stars whose centres are connected by flexible spacers into a necklace. We demonstrate that such starlike mode of branching leads to novel features both in conformations of individual bottle-brushes in solution and in appearance of additional scaling regime for brushes formed by bottle-brushes tethered to the surface.     

Scaling of the viscoelasticity of highly filled carbon black polyethylene composites above the melting point

Different types of linear low-density polyethylene and ethylene butylacrylate copolymers were mixed with various types of carbon black in amounts between 25 and 40% by weight. Viscoelastic properties were measured using dynamic mechanical analysis applying a frequency sweep. Typically, the complex modulus approaches asymptotically a constant value at small frequencies, which is referred to as ‘yield modulus’. These results were analysed using a scaling approach according to which the complex modulus and the frequency are normalised by the yield modulus and the quotient of the yield modulus and the polymer viscosity, respectively. Thus a master curve is achieved for nearly all samples independent of the polymer and carbon black type and loading. A similar scaling behaviour has been observed earlier for differently concentrated suspensions of carbon black in Newtonian liquids, but not for filled polymers and different carbon blacks. Thus, contributions from polymer and carbon black to the compounds' viscoelastic properties are discussed.     

Scaling laws for network model permeability: application to wellbore oil flow simulation with solid deposition

Network absolute permeability, evaluated by solving the Kirchhoff's equations for several network realizations, was correlated with some network parameters using scaling laws. Two kinds of site-bond network assembling algorithms were used to build networks with and without spatial correlation of their element size distributions. Simple models for solid deposition damage were applied to generate morphology-evolving processes for a given network. Simple functional forms were able to correlate the permeability for the two assembling algorithms and the damage processes. Such scaling laws allow the absolute permeability prediction from the network parameters, avoiding the time-consuming solution of the Kirchhoff's equations. This enables an efficient coupling of network models to flow simulation models for morphology-evolving problems. When this method was applied to a model for wellbore flow under asphaltene deposition, a speed up between 7 and 25 times was achieved.     

Comparison of two cationic polymeric flocculant architectures on the destabilization of negatively charged latex suspensions

Flocculation studies between cationic polymers and oppositely charged colloidal particles are reported in which both flocculation kinetics and floc structures are systematically investigated. The flocculation rate constant, stability ratio and kinetics laws are experimentally determined using particle counting for two polymer architectures; a cationic linear polymer and a two-branched polymer. Comparisons are also made using NaCl at different ionic concentrations for the destabilization of the colloidal particles. Detailed measurements of electrophoretic mobility and kinetics rate constants on varying the polymer dosage are reported. Results suggest that the polymer architecture plays important roles on the polymer dosage for the rapid destabilization of the colloidal suspension. The branched polymer at optimal dosage exhibits the highest flocculation rate constant, whereas on the other hand, the linear polymer concentration range of flocculation is larger. In both cases, polymer flocculation is more efficient by a factor of 5-6 than charge screening effects due to the presence of salt. Analysis of the stability ratio indicates that tele-bridging flocculation and electrostatic forces dictate the stability of the charged latex particle suspension. It is shown that the fractal concepts which are valid for aggregation processes are also applicable here and branched polymers as well as linear polymers yield to the formation of compact flocs in comparison to those obtained with salt.