Characterization of plasma protein gels by means of image analysis

In this study, image analysis is presented as a powerful tool to analyse changes in the microstructural properties of protein gels. Several methods were used to elucidate changes in plasma protein gels induced by changes in the pH conditions, visually noticeable but difficult to assess objectively. Fractal analysis was used to measure the degree of self-similarity, lacunarity analysis to study the distribution of pores within the protein network and the spatial variability of SEM images to describe the compactness of the gel. It was found that the lacunarity measurements and the cut-off of the autocorrelation functions complemented the fractal dimension (D_f) and the average pore size, the most used parameters in describing the microstructure of protein gels. Correlations between macroscopic properties and microstructural attributes revealed that an increase in textural attributes, such as hardness, springiness and cohesiveness, and in the capacity of gels to retain water, entailed an increase of D_f and the compactness of gels, but a decrease in the pore size and the heterogeneity of gaps.     

岩石破碎块度特性及计算方法

块度分布是衡量岩石破碎产物破碎程度的重要标志，本文分析了两种不同破碎条件下岩石破碎产物分布函数的计算方法。     

μCT技术研究煤的孔隙结构和分形特征

煤的孔隙结构是影响煤中气体吸附和渗流的一个重要因素。从实现精细化、无损化和定量化入手,应用μCT 225kVFCB型高精度CT试验分析系统,通过显微CT切片,提取研究了4个煤样孔隙分布特征,讨论了煤级、煤显微组分和灰分对煤孔隙结构的影响程度。采用公约数网格序列盒维数法定量表征了孔隙结构的复杂程度和不规则性,探讨了孔隙率、渗透率和分形维数的关系。研究表明,研究煤样的孔隙分布总体受煤显微组分含量控制,同时煤中矿物充填作用在一定程度上降低了煤的孔隙率、平均孔径和孔隙数量。煤孔隙分形维数D的变化与孔隙分布特征密切相关,有效地反映了孔隙结构的非均质性。孔隙率、渗透率与分形维数呈现显著的幂指数正相关关系。由此指示,基于显微CT切片的煤孔隙分形维数可作为煤储层孔隙特征和渗透性评价的定量指标之一。     

发动机气门漏气诊断的关联积分法

本文在信号相空间重构的基础上，求出关联积分，然后将关联积分作为一个特征集处理，并从中提取诊断特征量，进行气门漏气故障诊断。诊断实例表明该方法是可行的，并取得了较好的效果。     

On the fractal characteristics of low Damköhler number flames

Knowledge of the fractal properties of premixed flame surfaces can potentially be used to help develop turbulent combustion models. Here, direct numerical simulations of low Damköhler number flames are used to analyse the fractal nature of the flames. Two sets of data are considered: (i) thermochemical hydrogen–air turbulent premixed plane-jet flames with detailed chemistry and (ii) thermonuclear flames in type Ia supernovae. A three-dimensional box counting method is used to investigate fractal dimension of the flame surface, characterising the self similarity of flame fronts. In the premixed flames, the fractal dimension is found to vary in time between 2.1 and 2.7. The supernovae flames in distributed combustion regimes yield fractal dimension about 2.7. The results for the maximum fractal dimensions are higher than previously reported. They are explained theoretically by a Reynolds number similarity argument which posits that the high Reynolds number, low Damköhler number limiting value of the fractal dimension is 8/3. Also tested is Mandelbrot’s fractal additive law which relates the fractal dimension determined in two dimensions, which is typical of experimental measurements, to that in three dimensions. The comparison of the fractal dimension in both two-dimensional and three-dimensional spaces supports the additive law, even though the flames considered do not formally satisfy isotropy. Finally, the inner-cut off is extracted from the hydrogen flames and found to be consistent in order of magnitude with Kolmogorov scaling.     

邻域匹配和分类匹配的分形块编码

值域块的分形编码，是值域块与定义域块池中的定义域块逐一匹配后产生的。这一匹配过程是影响分形块编码速度的深层原因，此文改全局匹配为邻域匹配和分类匹配，从二条途径探讨了缩短匹配时间的方法。实验结果表明，领域匹配及分类匹配的分形块编码的时间，但信噪比略有下降。     

基于分形理论的柴油引燃天然气发动机燃烧模型

以柴油引燃天然气发动机为研究对象,针对柴油引燃油的扩散燃烧和天然气气体燃料的均质预混燃烧的特点,分别建立了引燃油多区燃烧模型和基于分形理论的预混天然气气体燃料燃烧模型.在试验验证所建模型的基础上,分析了引燃油量、喷油提前角和发动机转速对柴油引燃天然气发动机性能的影响.研究表明,适当增加引燃油量和减小喷油提前角可以降低柴油引燃天然气发动机的最大缸内压力升高率,从而有利于遏制柴油引燃天然气发动机高负荷时的爆震倾向.     

钙基脱硫剂分形孔结构的实验研究

分形维数是描述分形结构特性的一个重要参数,其反映了结构的规则程度,文章通过实验的方法,研究了钙基脱硫剂孔结构分形维数的变化特性,以及分形特性对脱硫剂的硫化能力的影响,结果表明CaO孔隙的平均孔径越大,分形维数会越小;脱硫剂硫化过程中形成的不可进入孔隙量随着分形维数的增大而增大。     

内燃机燃烧火焰的分形特征研究

介绍了发动机湍流预混燃烧火焰分形研究的进展,分析了湍流火焰分维测量的数盒子法、修正数盒子法及其优缺点,讨论了火焰特征尺度、内外截点的尺度及维数D与各参数之间的关系。